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author | Jean Delvare <khali@linux-fr.org> | 2009-12-06 17:06:24 +0100 |
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committer | Jean Delvare <khali@linux-fr.org> | 2009-12-06 17:06:24 +0100 |
commit | c7b25a9e96dc89954ae8d8f473f56fae62030f84 (patch) | |
tree | cc1f924445517a16e3923112e77edbfe33cd3b25 /Documentation/i2c/old-module-parameters | |
parent | abe38388e50f4d89726fd0c0cceea61563c7026b (diff) | |
download | linux-c7b25a9e96dc89954ae8d8f473f56fae62030f84.tar.bz2 |
i2c: Drop probe, ignore and force module parameters
The legacy probe and force module parameters are obsolete now, the
same can be achieved using the new_device sysfs interface, which is
both more flexible and cheaper (it is implemented by i2c-core rather
than replicated in every driver module.)
The legacy ignore module parameters can be dropped as well. Ignoring
can be done by instantiating a "dummy" device at the problematic
address.
This is the first step of a huge cleanup to i2c-core's i2c_detect
function, i2c.h's I2C_CLIENT_INSMOD* macros, and all drivers that made
use of them.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Diffstat (limited to 'Documentation/i2c/old-module-parameters')
-rw-r--r-- | Documentation/i2c/old-module-parameters | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/Documentation/i2c/old-module-parameters b/Documentation/i2c/old-module-parameters new file mode 100644 index 000000000000..8e2b629d533c --- /dev/null +++ b/Documentation/i2c/old-module-parameters @@ -0,0 +1,44 @@ +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". |