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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/i2c/old-module-parameters.rst | |
parent | Initial commit. (diff) | |
download | linux-upstream/5.10.209.tar.xz linux-upstream/5.10.209.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | Documentation/i2c/old-module-parameters.rst | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/Documentation/i2c/old-module-parameters.rst b/Documentation/i2c/old-module-parameters.rst new file mode 100644 index 000000000..38e55829d --- /dev/null +++ b/Documentation/i2c/old-module-parameters.rst @@ -0,0 +1,54 @@ +================================================================ +I2C device driver binding control from user-space in old kernels +================================================================ + +.. NOTE:: + Note: this section is only relevant if you are handling some old code + found in kernel 2.6. If you work with more recent kernels, you can + safely skip this section. + +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 :doc:`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``. |