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authorLinus Torvalds <torvalds@linux-foundation.org>2009-12-08 11:12:16 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-08 11:12:16 -0500
commit41440ffe21f29bdb985cab76b2d0b06d83e63b19 (patch)
tree1d7d1ff6f699ccbabb71c7bc4172f7d15bc4bc45 /Documentation/i2c/old-module-parameters
parentdad3de7d0090280f44ff27131ed2878f1ab6ddad (diff)
parent6471b68982d3bb1a593c3e183c804ecf830125d3 (diff)
Merge branch 'i2c-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging
* 'i2c-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging: i2c-stub: Documentation update i2c-stub: Allow user to disable some commands i2c-stub: Implement I2C block support i2c: Refactor for_each callbacks i2c-i801: Retry on lost arbitration i2c: Remove big kernel lock from i2cdev_open ics932s401: Clean up detect function i2c: Simplify i2c_detect_address i2c: Drop probe, ignore and force module parameters i2c: Add missing __devinit markers to old i2c adapter drivers i2c: Bus drivers don't have to support I2C_M_REV_DIR_ADDR i2c: Prevent priority inversion on top of bus lock i2c-voodoo3: Delete i2c-powermac: Drop temporary name buffer i2c-powermac: Include the i2c_adapter in struct pmac_i2c_bus i2c-powermac: Log errors i2c-powermac: Refactor i2c_powermac_smbus_xfer i2c-powermac: Reject unsupported I2C transactions i2c/chips: Move ds1682 to drivers/misc
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1I2C device driver binding control from user-space
2=================================================
3
4Up to kernel 2.6.32, many i2c drivers used helper macros provided by
5<linux/i2c.h> which created standard module parameters to let the user
6control how the driver would probe i2c buses and attach to devices. These
7parameters were known as "probe" (to let the driver probe for an extra
8address), "force" (to forcibly attach the driver to a given device) and
9"ignore" (to prevent a driver from probing a given address).
10
11With the conversion of the i2c subsystem to the standard device driver
12binding model, it became clear that these per-module parameters were no
13longer needed, and that a centralized implementation was possible. The new,
14sysfs-based interface is described in the documentation file
15"instantiating-devices", section "Method 4: Instantiate from user-space".
16
17Below is a mapping from the old module parameters to the new interface.
18
19Attaching a driver to an I2C device
20-----------------------------------
21
22Old method (module parameters):
23# modprobe <driver> probe=1,0x2d
24# modprobe <driver> force=1,0x2d
25# modprobe <driver> force_<device>=1,0x2d
26
27New method (sysfs interface):
28# echo <device> 0x2d > /sys/bus/i2c/devices/i2c-1/new_device
29
30Preventing a driver from attaching to an I2C device
31---------------------------------------------------
32
33Old method (module parameters):
34# modprobe <driver> ignore=1,0x2f
35
36New method (sysfs interface):
37# echo dummy 0x2f > /sys/bus/i2c/devices/i2c-1/new_device
38# modprobe <driver>
39
40Of course, it is important to instantiate the "dummy" device before loading
41the driver. The dummy device will be handled by i2c-core itself, preventing
42other drivers from binding to it later on. If there is a real device at the
43problematic address, and you want another driver to bind to it, then simply
44pass the name of the device in question instead of "dummy".