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Diffstat (limited to 'Documentation/i2c/old-module-parameters.rst')
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diff --git a/Documentation/i2c/old-module-parameters.rst b/Documentation/i2c/old-module-parameters.rst new file mode 100644 index 000000000000..a1939512ad66 --- /dev/null +++ b/Documentation/i2c/old-module-parameters.rst @@ -0,0 +1,49 @@ +================================================= +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". |