e97b81ddbb
This patch forces the user to specify what type of adapter is present when loading i2c-parport or i2c-parport-light. If none is specified, the driver init simply fails - instead of assuming adapter type 0. This alleviates the sometimes lengthy boot time delays which can be caused by accidentally building one of these into a kernel along with several i2c slave drivers that have lengthy probe routines (e.g. hwmon drivers). Kconfig and documentation updated accordingly. Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com> Signed-off-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
160 lines
6.6 KiB
Plaintext
160 lines
6.6 KiB
Plaintext
Kernel driver i2c-parport
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Author: Jean Delvare <khali@linux-fr.org>
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This is a unified driver for several i2c-over-parallel-port adapters,
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such as the ones made by Philips, Velleman or ELV. This driver is
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meant as a replacement for the older, individual drivers:
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* i2c-philips-par
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* i2c-elv
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* i2c-velleman
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* video/i2c-parport (NOT the same as this one, dedicated to home brew
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teletext adapters)
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It currently supports the following devices:
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* (type=0) Philips adapter
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* (type=1) home brew teletext adapter
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* (type=2) Velleman K8000 adapter
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* (type=3) ELV adapter
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* (type=4) Analog Devices ADM1032 evaluation board
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* (type=5) Analog Devices evaluation boards: ADM1025, ADM1030, ADM1031
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* (type=6) Barco LPT->DVI (K5800236) adapter
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These devices use different pinout configurations, so you have to tell
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the driver what you have, using the type module parameter. There is no
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way to autodetect the devices. Support for different pinout configurations
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can be easily added when needed.
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Earlier kernels defaulted to type=0 (Philips). But now, if the type
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parameter is missing, the driver will simply fail to initialize.
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Building your own adapter
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-------------------------
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If you want to build you own i2c-over-parallel-port adapter, here is
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a sample electronics schema (credits go to Sylvain Munaut):
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Device PC
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Side ___________________Vdd (+) Side
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--- --- ---
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|R| |R| |R|
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--- --- ---
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SCL ----------x--------o |-----------x------------------- pin 2
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SDA ----------x----x---| o---x--------------------------- pin 13
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---------o |----------------x-------------- pin 3
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\| | |
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--- ---
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|R| |R|
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--- ---
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### ###
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GND GND
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Remarks:
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- This is the exact pinout and electronics used on the Analog Devices
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evaluation boards.
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/|
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- All inverters -o |- must be 74HC05, they must be open collector output.
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\|
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- All resitors are 10k.
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- Pins 18-25 of the parallel port connected to GND.
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- Pins 4-9 (D2-D7) could be used as VDD is the driver drives them high.
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The ADM1032 evaluation board uses D4-D7. Beware that the amount of
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current you can draw from the parallel port is limited. Also note that
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all connected lines MUST BE driven at the same state, else you'll short
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circuit the output buffers! So plugging the I2C adapter after loading
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the i2c-parport module might be a good safety since data line state
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prior to init may be unknown.
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- This is 5V!
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- Obviously you cannot read SCL (so it's not really standard-compliant).
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Pretty easy to add, just copy the SDA part and use another input pin.
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That would give (ELV compatible pinout):
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Device PC
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Side ______________________________Vdd (+) Side
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--- --- --- ---
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|R| |R| |R| |R|
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--- --- --- ---
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SCL ----------x--------x--| o---x------------------------ pin 15
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| ---o |-------------x-------------- pin 2
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SDA ---------------x---x--| o--------x------------------- pin 10
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---o |------------------x--------- pin 3
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\| | |
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--- ---
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|R| |R|
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--- ---
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### ###
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GND GND
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If possible, you should use the same pinout configuration as existing
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adapters do, so you won't even have to change the code.
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Similar (but different) drivers
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-------------------------------
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This driver is NOT the same as the i2c-pport driver found in the i2c
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package. The i2c-pport driver makes use of modern parallel port features so
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that you don't need additional electronics. It has other restrictions
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however, and was not ported to Linux 2.6 (yet).
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This driver is also NOT the same as the i2c-pcf-epp driver found in the
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lm_sensors package. The i2c-pcf-epp driver doesn't use the parallel port as
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an I2C bus directly. Instead, it uses it to control an external I2C bus
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master. That driver was not ported to Linux 2.6 (yet) either.
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Legacy documentation for Velleman adapter
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-----------------------------------------
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Useful links:
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Velleman http://www.velleman.be/
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Velleman K8000 Howto http://howto.htlw16.ac.at/k8000-howto.html
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The project has lead to new libs for the Velleman K8000 and K8005:
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LIBK8000 v1.99.1 and LIBK8005 v0.21
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With these libs, you can control the K8000 interface card and the K8005
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stepper motor card with the simple commands which are in the original
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Velleman software, like SetIOchannel, ReadADchannel, SendStepCCWFull and
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many more, using /dev/velleman.
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http://home.wanadoo.nl/hihihi/libk8000.htm
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http://home.wanadoo.nl/hihihi/libk8005.htm
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http://struyve.mine.nu:8080/index.php?block=k8000
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http://sourceforge.net/projects/libk8005/
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