Documentation/i2c/old-module-parameters

   1 I2C device driver binding control from user-space
   2 =================================================
   3
   4 Up to kernel 2.6.32, many i2c drivers used helper macros provided by
   5 <linux/i2c.h> which created standard module parameters to let the user
   6 control how the driver would probe i2c buses and attach to devices. These
   7 parameters were known as "probe" (to let the driver probe for an extra
   8 address), "force" (to forcibly attach the driver to a given device) and
   9 "ignore" (to prevent a driver from probing a given address).
  10
  11 With the conversion of the i2c subsystem to the standard device driver
  12 binding model, it became clear that these per-module parameters were no
  13 longer needed, and that a centralized implementation was possible. The new,
  14 sysfs-based interface is described in the documentation file
  15 "instantiating-devices", section "Method 4: Instantiate from user-space".
  16
  17 Below is a mapping from the old module parameters to the new interface.
  18
  19 Attaching a driver to an I2C device
  20 -----------------------------------
  21
  22 Old method (module parameters):
  23 # modprobe <driver> probe=1,0x2d
  24 # modprobe <driver> force=1,0x2d
  25 # modprobe <driver> force_<device>=1,0x2d
  26
  27 New method (sysfs interface):
  28 # echo <device> 0x2d > /sys/bus/i2c/devices/i2c-1/new_device
  29
  30 Preventing a driver from attaching to an I2C device
  31 ---------------------------------------------------
  32
  33 Old method (module parameters):
  34 # modprobe <driver> ignore=1,0x2f
  35
  36 New method (sysfs interface):
  37 # echo dummy 0x2f > /sys/bus/i2c/devices/i2c-1/new_device
  38 # modprobe <driver>
  39
  40 Of course, it is important to instantiate the "dummy" device before loading
  41 the driver. The dummy device will be handled by i2c-core itself, preventing
  42 other drivers from binding to it later on. If there is a real device at the
  43 problematic address, and you want another driver to bind to it, then simply
  44 pass the name of the device in question instead of "dummy".