1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
817 lines
31 KiB
Plaintext
817 lines
31 KiB
Plaintext
This is a small guide for those who want to write kernel drivers for I2C
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or SMBus devices.
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To set up a driver, you need to do several things. Some are optional, and
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some things can be done slightly or completely different. Use this as a
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guide, not as a rule book!
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General remarks
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===============
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Try to keep the kernel namespace as clean as possible. The best way to
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do this is to use a unique prefix for all global symbols. This is
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especially important for exported symbols, but it is a good idea to do
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it for non-exported symbols too. We will use the prefix `foo_' in this
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tutorial, and `FOO_' for preprocessor variables.
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The driver structure
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====================
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Usually, you will implement a single driver structure, and instantiate
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all clients from it. Remember, a driver structure contains general access
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routines, a client structure specific information like the actual I2C
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address.
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static struct i2c_driver foo_driver = {
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.owner = THIS_MODULE,
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.name = "Foo version 2.3 driver",
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.id = I2C_DRIVERID_FOO, /* from i2c-id.h, optional */
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.flags = I2C_DF_NOTIFY,
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.attach_adapter = &foo_attach_adapter,
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.detach_client = &foo_detach_client,
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.command = &foo_command /* may be NULL */
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}
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The name can be chosen freely, and may be upto 40 characters long. Please
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use something descriptive here.
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If used, the id should be a unique ID. The range 0xf000 to 0xffff is
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reserved for local use, and you can use one of those until you start
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distributing the driver, at which time you should contact the i2c authors
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to get your own ID(s). Note that most of the time you don't need an ID
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at all so you can just omit it.
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Don't worry about the flags field; just put I2C_DF_NOTIFY into it. This
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means that your driver will be notified when new adapters are found.
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This is almost always what you want.
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All other fields are for call-back functions which will be explained
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below.
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There use to be two additional fields in this structure, inc_use et dec_use,
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for module usage count, but these fields were obsoleted and removed.
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Extra client data
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=================
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The client structure has a special `data' field that can point to any
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structure at all. You can use this to keep client-specific data. You
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do not always need this, but especially for `sensors' drivers, it can
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be very useful.
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An example structure is below.
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struct foo_data {
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struct semaphore lock; /* For ISA access in `sensors' drivers. */
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int sysctl_id; /* To keep the /proc directory entry for
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`sensors' drivers. */
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enum chips type; /* To keep the chips type for `sensors' drivers. */
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/* Because the i2c bus is slow, it is often useful to cache the read
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information of a chip for some time (for example, 1 or 2 seconds).
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It depends of course on the device whether this is really worthwhile
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or even sensible. */
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struct semaphore update_lock; /* When we are reading lots of information,
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another process should not update the
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below information */
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char valid; /* != 0 if the following fields are valid. */
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unsigned long last_updated; /* In jiffies */
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/* Add the read information here too */
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};
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Accessing the client
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====================
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Let's say we have a valid client structure. At some time, we will need
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to gather information from the client, or write new information to the
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client. How we will export this information to user-space is less
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important at this moment (perhaps we do not need to do this at all for
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some obscure clients). But we need generic reading and writing routines.
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I have found it useful to define foo_read and foo_write function for this.
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For some cases, it will be easier to call the i2c functions directly,
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but many chips have some kind of register-value idea that can easily
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be encapsulated. Also, some chips have both ISA and I2C interfaces, and
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it useful to abstract from this (only for `sensors' drivers).
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The below functions are simple examples, and should not be copied
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literally.
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int foo_read_value(struct i2c_client *client, u8 reg)
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{
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if (reg < 0x10) /* byte-sized register */
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return i2c_smbus_read_byte_data(client,reg);
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else /* word-sized register */
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return i2c_smbus_read_word_data(client,reg);
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}
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int foo_write_value(struct i2c_client *client, u8 reg, u16 value)
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{
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if (reg == 0x10) /* Impossible to write - driver error! */ {
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return -1;
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else if (reg < 0x10) /* byte-sized register */
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return i2c_smbus_write_byte_data(client,reg,value);
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else /* word-sized register */
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return i2c_smbus_write_word_data(client,reg,value);
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}
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For sensors code, you may have to cope with ISA registers too. Something
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like the below often works. Note the locking!
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int foo_read_value(struct i2c_client *client, u8 reg)
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{
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int res;
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if (i2c_is_isa_client(client)) {
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down(&(((struct foo_data *) (client->data)) -> lock));
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outb_p(reg,client->addr + FOO_ADDR_REG_OFFSET);
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res = inb_p(client->addr + FOO_DATA_REG_OFFSET);
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up(&(((struct foo_data *) (client->data)) -> lock));
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return res;
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} else
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return i2c_smbus_read_byte_data(client,reg);
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}
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Writing is done the same way.
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Probing and attaching
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=====================
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Most i2c devices can be present on several i2c addresses; for some this
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is determined in hardware (by soldering some chip pins to Vcc or Ground),
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for others this can be changed in software (by writing to specific client
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registers). Some devices are usually on a specific address, but not always;
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and some are even more tricky. So you will probably need to scan several
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i2c addresses for your clients, and do some sort of detection to see
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whether it is actually a device supported by your driver.
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To give the user a maximum of possibilities, some default module parameters
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are defined to help determine what addresses are scanned. Several macros
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are defined in i2c.h to help you support them, as well as a generic
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detection algorithm.
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You do not have to use this parameter interface; but don't try to use
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function i2c_probe() (or i2c_detect()) if you don't.
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NOTE: If you want to write a `sensors' driver, the interface is slightly
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different! See below.
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Probing classes (i2c)
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---------------------
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All parameters are given as lists of unsigned 16-bit integers. Lists are
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terminated by I2C_CLIENT_END.
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The following lists are used internally:
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normal_i2c: filled in by the module writer.
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A list of I2C addresses which should normally be examined.
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normal_i2c_range: filled in by the module writer.
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A list of pairs of I2C addresses, each pair being an inclusive range of
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addresses which should normally be examined.
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probe: insmod parameter.
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A list of pairs. The first value is a bus number (-1 for any I2C bus),
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the second is the address. These addresses are also probed, as if they
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were in the 'normal' list.
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probe_range: insmod parameter.
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A list of triples. The first value is a bus number (-1 for any I2C bus),
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the second and third are addresses. These form an inclusive range of
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addresses that are also probed, as if they were in the 'normal' list.
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ignore: insmod parameter.
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A list of pairs. The first value is a bus number (-1 for any I2C bus),
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the second is the I2C address. These addresses are never probed.
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This parameter overrules 'normal' and 'probe', but not the 'force' lists.
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ignore_range: insmod parameter.
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A list of triples. The first value is a bus number (-1 for any I2C bus),
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the second and third are addresses. These form an inclusive range of
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I2C addresses that are never probed.
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This parameter overrules 'normal' and 'probe', but not the 'force' lists.
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force: insmod parameter.
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A list of pairs. The first value is a bus number (-1 for any I2C bus),
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the second is the I2C address. A device is blindly assumed to be on
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the given address, no probing is done.
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Fortunately, as a module writer, you just have to define the `normal'
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and/or `normal_range' parameters. The complete declaration could look
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like this:
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/* Scan 0x20 to 0x2f, 0x37, and 0x40 to 0x4f */
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static unsigned short normal_i2c[] = { 0x37,I2C_CLIENT_END };
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static unsigned short normal_i2c_range[] = { 0x20, 0x2f, 0x40, 0x4f,
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I2C_CLIENT_END };
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/* Magic definition of all other variables and things */
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I2C_CLIENT_INSMOD;
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Note that you *have* to call the two defined variables `normal_i2c' and
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`normal_i2c_range', without any prefix!
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Probing classes (sensors)
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-------------------------
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If you write a `sensors' driver, you use a slightly different interface.
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As well as I2C addresses, we have to cope with ISA addresses. Also, we
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use a enum of chip types. Don't forget to include `sensors.h'.
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The following lists are used internally. They are all lists of integers.
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normal_i2c: filled in by the module writer. Terminated by SENSORS_I2C_END.
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A list of I2C addresses which should normally be examined.
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normal_i2c_range: filled in by the module writer. Terminated by
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SENSORS_I2C_END
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A list of pairs of I2C addresses, each pair being an inclusive range of
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addresses which should normally be examined.
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normal_isa: filled in by the module writer. Terminated by SENSORS_ISA_END.
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A list of ISA addresses which should normally be examined.
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normal_isa_range: filled in by the module writer. Terminated by
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SENSORS_ISA_END
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A list of triples. The first two elements are ISA addresses, being an
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range of addresses which should normally be examined. The third is the
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modulo parameter: only addresses which are 0 module this value relative
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to the first address of the range are actually considered.
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probe: insmod parameter. Initialize this list with SENSORS_I2C_END values.
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A list of pairs. The first value is a bus number (SENSORS_ISA_BUS for
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the ISA bus, -1 for any I2C bus), the second is the address. These
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addresses are also probed, as if they were in the 'normal' list.
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probe_range: insmod parameter. Initialize this list with SENSORS_I2C_END
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values.
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A list of triples. The first value is a bus number (SENSORS_ISA_BUS for
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the ISA bus, -1 for any I2C bus), the second and third are addresses.
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These form an inclusive range of addresses that are also probed, as
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if they were in the 'normal' list.
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ignore: insmod parameter. Initialize this list with SENSORS_I2C_END values.
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A list of pairs. The first value is a bus number (SENSORS_ISA_BUS for
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the ISA bus, -1 for any I2C bus), the second is the I2C address. These
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addresses are never probed. This parameter overrules 'normal' and
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'probe', but not the 'force' lists.
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ignore_range: insmod parameter. Initialize this list with SENSORS_I2C_END
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values.
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A list of triples. The first value is a bus number (SENSORS_ISA_BUS for
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the ISA bus, -1 for any I2C bus), the second and third are addresses.
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These form an inclusive range of I2C addresses that are never probed.
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This parameter overrules 'normal' and 'probe', but not the 'force' lists.
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Also used is a list of pointers to sensors_force_data structures:
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force_data: insmod parameters. A list, ending with an element of which
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the force field is NULL.
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Each element contains the type of chip and a list of pairs.
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The first value is a bus number (SENSORS_ISA_BUS for the ISA bus,
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-1 for any I2C bus), the second is the address.
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These are automatically translated to insmod variables of the form
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force_foo.
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So we have a generic insmod variabled `force', and chip-specific variables
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`force_CHIPNAME'.
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Fortunately, as a module writer, you just have to define the `normal'
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and/or `normal_range' parameters, and define what chip names are used.
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The complete declaration could look like this:
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/* Scan i2c addresses 0x20 to 0x2f, 0x37, and 0x40 to 0x4f
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static unsigned short normal_i2c[] = {0x37,SENSORS_I2C_END};
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static unsigned short normal_i2c_range[] = {0x20,0x2f,0x40,0x4f,
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SENSORS_I2C_END};
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/* Scan ISA address 0x290 */
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static unsigned int normal_isa[] = {0x0290,SENSORS_ISA_END};
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static unsigned int normal_isa_range[] = {SENSORS_ISA_END};
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/* Define chips foo and bar, as well as all module parameters and things */
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SENSORS_INSMOD_2(foo,bar);
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If you have one chip, you use macro SENSORS_INSMOD_1(chip), if you have 2
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you use macro SENSORS_INSMOD_2(chip1,chip2), etc. If you do not want to
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bother with chip types, you can use SENSORS_INSMOD_0.
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A enum is automatically defined as follows:
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enum chips { any_chip, chip1, chip2, ... }
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Attaching to an adapter
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-----------------------
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Whenever a new adapter is inserted, or for all adapters if the driver is
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being registered, the callback attach_adapter() is called. Now is the
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time to determine what devices are present on the adapter, and to register
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a client for each of them.
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The attach_adapter callback is really easy: we just call the generic
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detection function. This function will scan the bus for us, using the
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information as defined in the lists explained above. If a device is
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detected at a specific address, another callback is called.
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int foo_attach_adapter(struct i2c_adapter *adapter)
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{
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return i2c_probe(adapter,&addr_data,&foo_detect_client);
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}
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For `sensors' drivers, use the i2c_detect function instead:
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int foo_attach_adapter(struct i2c_adapter *adapter)
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{
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return i2c_detect(adapter,&addr_data,&foo_detect_client);
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}
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Remember, structure `addr_data' is defined by the macros explained above,
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so you do not have to define it yourself.
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The i2c_probe or i2c_detect function will call the foo_detect_client
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function only for those i2c addresses that actually have a device on
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them (unless a `force' parameter was used). In addition, addresses that
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are already in use (by some other registered client) are skipped.
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The detect client function
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--------------------------
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The detect client function is called by i2c_probe or i2c_detect.
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The `kind' parameter contains 0 if this call is due to a `force'
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parameter, and -1 otherwise (for i2c_detect, it contains 0 if
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this call is due to the generic `force' parameter, and the chip type
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number if it is due to a specific `force' parameter).
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Below, some things are only needed if this is a `sensors' driver. Those
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parts are between /* SENSORS ONLY START */ and /* SENSORS ONLY END */
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markers.
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This function should only return an error (any value != 0) if there is
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some reason why no more detection should be done anymore. If the
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detection just fails for this address, return 0.
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For now, you can ignore the `flags' parameter. It is there for future use.
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int foo_detect_client(struct i2c_adapter *adapter, int address,
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unsigned short flags, int kind)
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{
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int err = 0;
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int i;
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struct i2c_client *new_client;
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struct foo_data *data;
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const char *client_name = ""; /* For non-`sensors' drivers, put the real
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name here! */
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/* Let's see whether this adapter can support what we need.
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Please substitute the things you need here!
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For `sensors' drivers, add `! is_isa &&' to the if statement */
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if (!i2c_check_functionality(adapter,I2C_FUNC_SMBUS_WORD_DATA |
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I2C_FUNC_SMBUS_WRITE_BYTE))
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goto ERROR0;
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/* SENSORS ONLY START */
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const char *type_name = "";
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int is_isa = i2c_is_isa_adapter(adapter);
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if (is_isa) {
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/* If this client can't be on the ISA bus at all, we can stop now
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(call `goto ERROR0'). But for kicks, we will assume it is all
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right. */
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/* Discard immediately if this ISA range is already used */
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if (check_region(address,FOO_EXTENT))
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goto ERROR0;
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/* Probe whether there is anything on this address.
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Some example code is below, but you will have to adapt this
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for your own driver */
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if (kind < 0) /* Only if no force parameter was used */ {
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/* We may need long timeouts at least for some chips. */
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#define REALLY_SLOW_IO
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i = inb_p(address + 1);
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if (inb_p(address + 2) != i)
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goto ERROR0;
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if (inb_p(address + 3) != i)
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goto ERROR0;
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if (inb_p(address + 7) != i)
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goto ERROR0;
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#undef REALLY_SLOW_IO
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/* Let's just hope nothing breaks here */
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i = inb_p(address + 5) & 0x7f;
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outb_p(~i & 0x7f,address+5);
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if ((inb_p(address + 5) & 0x7f) != (~i & 0x7f)) {
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outb_p(i,address+5);
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return 0;
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}
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}
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}
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/* SENSORS ONLY END */
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/* OK. For now, we presume we have a valid client. We now create the
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client structure, even though we cannot fill it completely yet.
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But it allows us to access several i2c functions safely */
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/* Note that we reserve some space for foo_data too. If you don't
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need it, remove it. We do it here to help to lessen memory
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fragmentation. */
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if (! (new_client = kmalloc(sizeof(struct i2c_client) +
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sizeof(struct foo_data),
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GFP_KERNEL))) {
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err = -ENOMEM;
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goto ERROR0;
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}
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/* This is tricky, but it will set the data to the right value. */
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client->data = new_client + 1;
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data = (struct foo_data *) (client->data);
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new_client->addr = address;
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new_client->data = data;
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new_client->adapter = adapter;
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new_client->driver = &foo_driver;
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new_client->flags = 0;
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/* Now, we do the remaining detection. If no `force' parameter is used. */
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/* First, the generic detection (if any), that is skipped if any force
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parameter was used. */
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if (kind < 0) {
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/* The below is of course bogus */
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if (foo_read(new_client,FOO_REG_GENERIC) != FOO_GENERIC_VALUE)
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goto ERROR1;
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}
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/* SENSORS ONLY START */
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/* Next, specific detection. This is especially important for `sensors'
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devices. */
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/* Determine the chip type. Not needed if a `force_CHIPTYPE' parameter
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was used. */
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if (kind <= 0) {
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i = foo_read(new_client,FOO_REG_CHIPTYPE);
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if (i == FOO_TYPE_1)
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kind = chip1; /* As defined in the enum */
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else if (i == FOO_TYPE_2)
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kind = chip2;
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else {
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printk("foo: Ignoring 'force' parameter for unknown chip at "
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"adapter %d, address 0x%02x\n",i2c_adapter_id(adapter),address);
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goto ERROR1;
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}
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}
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|
|
/* Now set the type and chip names */
|
|
if (kind == chip1) {
|
|
type_name = "chip1"; /* For /proc entry */
|
|
client_name = "CHIP 1";
|
|
} else if (kind == chip2) {
|
|
type_name = "chip2"; /* For /proc entry */
|
|
client_name = "CHIP 2";
|
|
}
|
|
|
|
/* Reserve the ISA region */
|
|
if (is_isa)
|
|
request_region(address,FOO_EXTENT,type_name);
|
|
|
|
/* SENSORS ONLY END */
|
|
|
|
/* Fill in the remaining client fields. */
|
|
strcpy(new_client->name,client_name);
|
|
|
|
/* SENSORS ONLY BEGIN */
|
|
data->type = kind;
|
|
/* SENSORS ONLY END */
|
|
|
|
data->valid = 0; /* Only if you use this field */
|
|
init_MUTEX(&data->update_lock); /* Only if you use this field */
|
|
|
|
/* Any other initializations in data must be done here too. */
|
|
|
|
/* Tell the i2c layer a new client has arrived */
|
|
if ((err = i2c_attach_client(new_client)))
|
|
goto ERROR3;
|
|
|
|
/* SENSORS ONLY BEGIN */
|
|
/* Register a new directory entry with module sensors. See below for
|
|
the `template' structure. */
|
|
if ((i = i2c_register_entry(new_client, type_name,
|
|
foo_dir_table_template,THIS_MODULE)) < 0) {
|
|
err = i;
|
|
goto ERROR4;
|
|
}
|
|
data->sysctl_id = i;
|
|
|
|
/* SENSORS ONLY END */
|
|
|
|
/* This function can write default values to the client registers, if
|
|
needed. */
|
|
foo_init_client(new_client);
|
|
return 0;
|
|
|
|
/* OK, this is not exactly good programming practice, usually. But it is
|
|
very code-efficient in this case. */
|
|
|
|
ERROR4:
|
|
i2c_detach_client(new_client);
|
|
ERROR3:
|
|
ERROR2:
|
|
/* SENSORS ONLY START */
|
|
if (is_isa)
|
|
release_region(address,FOO_EXTENT);
|
|
/* SENSORS ONLY END */
|
|
ERROR1:
|
|
kfree(new_client);
|
|
ERROR0:
|
|
return err;
|
|
}
|
|
|
|
|
|
Removing the client
|
|
===================
|
|
|
|
The detach_client call back function is called when a client should be
|
|
removed. It may actually fail, but only when panicking. This code is
|
|
much simpler than the attachment code, fortunately!
|
|
|
|
int foo_detach_client(struct i2c_client *client)
|
|
{
|
|
int err,i;
|
|
|
|
/* SENSORS ONLY START */
|
|
/* Deregister with the `i2c-proc' module. */
|
|
i2c_deregister_entry(((struct lm78_data *)(client->data))->sysctl_id);
|
|
/* SENSORS ONLY END */
|
|
|
|
/* Try to detach the client from i2c space */
|
|
if ((err = i2c_detach_client(client))) {
|
|
printk("foo.o: Client deregistration failed, client not detached.\n");
|
|
return err;
|
|
}
|
|
|
|
/* SENSORS ONLY START */
|
|
if i2c_is_isa_client(client)
|
|
release_region(client->addr,LM78_EXTENT);
|
|
/* SENSORS ONLY END */
|
|
|
|
kfree(client); /* Frees client data too, if allocated at the same time */
|
|
return 0;
|
|
}
|
|
|
|
|
|
Initializing the module or kernel
|
|
=================================
|
|
|
|
When the kernel is booted, or when your foo driver module is inserted,
|
|
you have to do some initializing. Fortunately, just attaching (registering)
|
|
the driver module is usually enough.
|
|
|
|
/* Keep track of how far we got in the initialization process. If several
|
|
things have to initialized, and we fail halfway, only those things
|
|
have to be cleaned up! */
|
|
static int __initdata foo_initialized = 0;
|
|
|
|
static int __init foo_init(void)
|
|
{
|
|
int res;
|
|
printk("foo version %s (%s)\n",FOO_VERSION,FOO_DATE);
|
|
|
|
if ((res = i2c_add_driver(&foo_driver))) {
|
|
printk("foo: Driver registration failed, module not inserted.\n");
|
|
foo_cleanup();
|
|
return res;
|
|
}
|
|
foo_initialized ++;
|
|
return 0;
|
|
}
|
|
|
|
void foo_cleanup(void)
|
|
{
|
|
if (foo_initialized == 1) {
|
|
if ((res = i2c_del_driver(&foo_driver))) {
|
|
printk("foo: Driver registration failed, module not removed.\n");
|
|
return;
|
|
}
|
|
foo_initialized --;
|
|
}
|
|
}
|
|
|
|
/* Substitute your own name and email address */
|
|
MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl>"
|
|
MODULE_DESCRIPTION("Driver for Barf Inc. Foo I2C devices");
|
|
|
|
module_init(foo_init);
|
|
module_exit(foo_cleanup);
|
|
|
|
Note that some functions are marked by `__init', and some data structures
|
|
by `__init_data'. Hose functions and structures can be removed after
|
|
kernel booting (or module loading) is completed.
|
|
|
|
Command function
|
|
================
|
|
|
|
A generic ioctl-like function call back is supported. You will seldom
|
|
need this. You may even set it to NULL.
|
|
|
|
/* No commands defined */
|
|
int foo_command(struct i2c_client *client, unsigned int cmd, void *arg)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
|
|
Sending and receiving
|
|
=====================
|
|
|
|
If you want to communicate with your device, there are several functions
|
|
to do this. You can find all of them in i2c.h.
|
|
|
|
If you can choose between plain i2c communication and SMBus level
|
|
communication, please use the last. All adapters understand SMBus level
|
|
commands, but only some of them understand plain i2c!
|
|
|
|
|
|
Plain i2c communication
|
|
-----------------------
|
|
|
|
extern int i2c_master_send(struct i2c_client *,const char* ,int);
|
|
extern int i2c_master_recv(struct i2c_client *,char* ,int);
|
|
|
|
These routines read and write some bytes from/to a client. The client
|
|
contains the i2c address, so you do not have to include it. The second
|
|
parameter contains the bytes the read/write, the third the length of the
|
|
buffer. Returned is the actual number of bytes read/written.
|
|
|
|
extern int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msg,
|
|
int num);
|
|
|
|
This sends a series of messages. Each message can be a read or write,
|
|
and they can be mixed in any way. The transactions are combined: no
|
|
stop bit is sent between transaction. The i2c_msg structure contains
|
|
for each message the client address, the number of bytes of the message
|
|
and the message data itself.
|
|
|
|
You can read the file `i2c-protocol' for more information about the
|
|
actual i2c protocol.
|
|
|
|
|
|
SMBus communication
|
|
-------------------
|
|
|
|
extern s32 i2c_smbus_xfer (struct i2c_adapter * adapter, u16 addr,
|
|
unsigned short flags,
|
|
char read_write, u8 command, int size,
|
|
union i2c_smbus_data * data);
|
|
|
|
This is the generic SMBus function. All functions below are implemented
|
|
in terms of it. Never use this function directly!
|
|
|
|
|
|
extern s32 i2c_smbus_write_quick(struct i2c_client * client, u8 value);
|
|
extern s32 i2c_smbus_read_byte(struct i2c_client * client);
|
|
extern s32 i2c_smbus_write_byte(struct i2c_client * client, u8 value);
|
|
extern s32 i2c_smbus_read_byte_data(struct i2c_client * client, u8 command);
|
|
extern s32 i2c_smbus_write_byte_data(struct i2c_client * client,
|
|
u8 command, u8 value);
|
|
extern s32 i2c_smbus_read_word_data(struct i2c_client * client, u8 command);
|
|
extern s32 i2c_smbus_write_word_data(struct i2c_client * client,
|
|
u8 command, u16 value);
|
|
extern s32 i2c_smbus_write_block_data(struct i2c_client * client,
|
|
u8 command, u8 length,
|
|
u8 *values);
|
|
|
|
These ones were removed in Linux 2.6.10 because they had no users, but could
|
|
be added back later if needed:
|
|
|
|
extern s32 i2c_smbus_read_i2c_block_data(struct i2c_client * client,
|
|
u8 command, u8 *values);
|
|
extern s32 i2c_smbus_read_block_data(struct i2c_client * client,
|
|
u8 command, u8 *values);
|
|
extern s32 i2c_smbus_write_i2c_block_data(struct i2c_client * client,
|
|
u8 command, u8 length,
|
|
u8 *values);
|
|
extern s32 i2c_smbus_process_call(struct i2c_client * client,
|
|
u8 command, u16 value);
|
|
extern s32 i2c_smbus_block_process_call(struct i2c_client *client,
|
|
u8 command, u8 length,
|
|
u8 *values)
|
|
|
|
All these transactions return -1 on failure. The 'write' transactions
|
|
return 0 on success; the 'read' transactions return the read value, except
|
|
for read_block, which returns the number of values read. The block buffers
|
|
need not be longer than 32 bytes.
|
|
|
|
You can read the file `smbus-protocol' for more information about the
|
|
actual SMBus protocol.
|
|
|
|
|
|
General purpose routines
|
|
========================
|
|
|
|
Below all general purpose routines are listed, that were not mentioned
|
|
before.
|
|
|
|
/* This call returns a unique low identifier for each registered adapter,
|
|
* or -1 if the adapter was not registered.
|
|
*/
|
|
extern int i2c_adapter_id(struct i2c_adapter *adap);
|
|
|
|
|
|
The sensors sysctl/proc interface
|
|
=================================
|
|
|
|
This section only applies if you write `sensors' drivers.
|
|
|
|
Each sensors driver creates a directory in /proc/sys/dev/sensors for each
|
|
registered client. The directory is called something like foo-i2c-4-65.
|
|
The sensors module helps you to do this as easily as possible.
|
|
|
|
The template
|
|
------------
|
|
|
|
You will need to define a ctl_table template. This template will automatically
|
|
be copied to a newly allocated structure and filled in where necessary when
|
|
you call sensors_register_entry.
|
|
|
|
First, I will give an example definition.
|
|
static ctl_table foo_dir_table_template[] = {
|
|
{ FOO_SYSCTL_FUNC1, "func1", NULL, 0, 0644, NULL, &i2c_proc_real,
|
|
&i2c_sysctl_real,NULL,&foo_func },
|
|
{ FOO_SYSCTL_FUNC2, "func2", NULL, 0, 0644, NULL, &i2c_proc_real,
|
|
&i2c_sysctl_real,NULL,&foo_func },
|
|
{ FOO_SYSCTL_DATA, "data", NULL, 0, 0644, NULL, &i2c_proc_real,
|
|
&i2c_sysctl_real,NULL,&foo_data },
|
|
{ 0 }
|
|
};
|
|
|
|
In the above example, three entries are defined. They can either be
|
|
accessed through the /proc interface, in the /proc/sys/dev/sensors/*
|
|
directories, as files named func1, func2 and data, or alternatively
|
|
through the sysctl interface, in the appropriate table, with identifiers
|
|
FOO_SYSCTL_FUNC1, FOO_SYSCTL_FUNC2 and FOO_SYSCTL_DATA.
|
|
|
|
The third, sixth and ninth parameters should always be NULL, and the
|
|
fourth should always be 0. The fifth is the mode of the /proc file;
|
|
0644 is safe, as the file will be owned by root:root.
|
|
|
|
The seventh and eighth parameters should be &i2c_proc_real and
|
|
&i2c_sysctl_real if you want to export lists of reals (scaled
|
|
integers). You can also use your own function for them, as usual.
|
|
Finally, the last parameter is the call-back to gather the data
|
|
(see below) if you use the *_proc_real functions.
|
|
|
|
|
|
Gathering the data
|
|
------------------
|
|
|
|
The call back functions (foo_func and foo_data in the above example)
|
|
can be called in several ways; the operation parameter determines
|
|
what should be done:
|
|
|
|
* If operation == SENSORS_PROC_REAL_INFO, you must return the
|
|
magnitude (scaling) in nrels_mag;
|
|
* If operation == SENSORS_PROC_REAL_READ, you must read information
|
|
from the chip and return it in results. The number of integers
|
|
to display should be put in nrels_mag;
|
|
* If operation == SENSORS_PROC_REAL_WRITE, you must write the
|
|
supplied information to the chip. nrels_mag will contain the number
|
|
of integers, results the integers themselves.
|
|
|
|
The *_proc_real functions will display the elements as reals for the
|
|
/proc interface. If you set the magnitude to 2, and supply 345 for
|
|
SENSORS_PROC_REAL_READ, it would display 3.45; and if the user would
|
|
write 45.6 to the /proc file, it would be returned as 4560 for
|
|
SENSORS_PROC_REAL_WRITE. A magnitude may even be negative!
|
|
|
|
An example function:
|
|
|
|
/* FOO_FROM_REG and FOO_TO_REG translate between scaled values and
|
|
register values. Note the use of the read cache. */
|
|
void foo_in(struct i2c_client *client, int operation, int ctl_name,
|
|
int *nrels_mag, long *results)
|
|
{
|
|
struct foo_data *data = client->data;
|
|
int nr = ctl_name - FOO_SYSCTL_FUNC1; /* reduce to 0 upwards */
|
|
|
|
if (operation == SENSORS_PROC_REAL_INFO)
|
|
*nrels_mag = 2;
|
|
else if (operation == SENSORS_PROC_REAL_READ) {
|
|
/* Update the readings cache (if necessary) */
|
|
foo_update_client(client);
|
|
/* Get the readings from the cache */
|
|
results[0] = FOO_FROM_REG(data->foo_func_base[nr]);
|
|
results[1] = FOO_FROM_REG(data->foo_func_more[nr]);
|
|
results[2] = FOO_FROM_REG(data->foo_func_readonly[nr]);
|
|
*nrels_mag = 2;
|
|
} else if (operation == SENSORS_PROC_REAL_WRITE) {
|
|
if (*nrels_mag >= 1) {
|
|
/* Update the cache */
|
|
data->foo_base[nr] = FOO_TO_REG(results[0]);
|
|
/* Update the chip */
|
|
foo_write_value(client,FOO_REG_FUNC_BASE(nr),data->foo_base[nr]);
|
|
}
|
|
if (*nrels_mag >= 2) {
|
|
/* Update the cache */
|
|
data->foo_more[nr] = FOO_TO_REG(results[1]);
|
|
/* Update the chip */
|
|
foo_write_value(client,FOO_REG_FUNC_MORE(nr),data->foo_more[nr]);
|
|
}
|
|
}
|
|
}
|