forked from mirrors/linux
ccf988b66d
Convert each file at I2C subsystem, renaming them to .rst and adding to the driver-api book. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Wolfram Sang <wsa@the-dreams.de> Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
49 lines
1.9 KiB
ReStructuredText
49 lines
1.9 KiB
ReStructuredText
=================================================
|
|
I2C device driver binding control from user-space
|
|
=================================================
|
|
|
|
Up to kernel 2.6.32, many i2c drivers used helper macros provided by
|
|
<linux/i2c.h> which created standard module parameters to let the user
|
|
control how the driver would probe i2c buses and attach to devices. These
|
|
parameters were known as "probe" (to let the driver probe for an extra
|
|
address), "force" (to forcibly attach the driver to a given device) and
|
|
"ignore" (to prevent a driver from probing a given address).
|
|
|
|
With the conversion of the i2c subsystem to the standard device driver
|
|
binding model, it became clear that these per-module parameters were no
|
|
longer needed, and that a centralized implementation was possible. The new,
|
|
sysfs-based interface is described in the documentation file
|
|
"instantiating-devices", section "Method 4: Instantiate from user-space".
|
|
|
|
Below is a mapping from the old module parameters to the new interface.
|
|
|
|
Attaching a driver to an I2C device
|
|
-----------------------------------
|
|
|
|
Old method (module parameters)::
|
|
|
|
# modprobe <driver> probe=1,0x2d
|
|
# modprobe <driver> force=1,0x2d
|
|
# modprobe <driver> force_<device>=1,0x2d
|
|
|
|
New method (sysfs interface)::
|
|
|
|
# echo <device> 0x2d > /sys/bus/i2c/devices/i2c-1/new_device
|
|
|
|
Preventing a driver from attaching to an I2C device
|
|
---------------------------------------------------
|
|
|
|
Old method (module parameters)::
|
|
|
|
# modprobe <driver> ignore=1,0x2f
|
|
|
|
New method (sysfs interface)::
|
|
|
|
# echo dummy 0x2f > /sys/bus/i2c/devices/i2c-1/new_device
|
|
# modprobe <driver>
|
|
|
|
Of course, it is important to instantiate the "dummy" device before loading
|
|
the driver. The dummy device will be handled by i2c-core itself, preventing
|
|
other drivers from binding to it later on. If there is a real device at the
|
|
problematic address, and you want another driver to bind to it, then simply
|
|
pass the name of the device in question instead of "dummy".
|