50 lines
1.9 KiB
ReStructuredText
50 lines
1.9 KiB
ReStructuredText
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=================================================
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I2C device driver binding control from user-space
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=================================================
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Up to kernel 2.6.32, many i2c drivers used helper macros provided by
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<linux/i2c.h> which created standard module parameters to let the user
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control how the driver would probe i2c buses and attach to devices. These
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parameters were known as "probe" (to let the driver probe for an extra
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address), "force" (to forcibly attach the driver to a given device) and
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"ignore" (to prevent a driver from probing a given address).
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With the conversion of the i2c subsystem to the standard device driver
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binding model, it became clear that these per-module parameters were no
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longer needed, and that a centralized implementation was possible. The new,
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sysfs-based interface is described in the documentation file
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"instantiating-devices", section "Method 4: Instantiate from user-space".
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Below is a mapping from the old module parameters to the new interface.
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Attaching a driver to an I2C device
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-----------------------------------
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Old method (module parameters)::
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# modprobe <driver> probe=1,0x2d
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# modprobe <driver> force=1,0x2d
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# modprobe <driver> force_<device>=1,0x2d
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New method (sysfs interface)::
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# echo <device> 0x2d > /sys/bus/i2c/devices/i2c-1/new_device
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Preventing a driver from attaching to an I2C device
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---------------------------------------------------
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Old method (module parameters)::
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# modprobe <driver> ignore=1,0x2f
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New method (sysfs interface)::
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# echo dummy 0x2f > /sys/bus/i2c/devices/i2c-1/new_device
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# modprobe <driver>
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Of course, it is important to instantiate the "dummy" device before loading
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the driver. The dummy device will be handled by i2c-core itself, preventing
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other drivers from binding to it later on. If there is a real device at the
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problematic address, and you want another driver to bind to it, then simply
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pass the name of the device in question instead of "dummy".
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