• Jean Delvare's avatar
    i2c-mux-gpio: Add support for dynamically allocated GPIO pins · e7ee5140
    Jean Delvare authored
    The code instantiating an i2c-mux-gpio platform device doesn't
    necessarily know in advance the GPIO pin numbers it wants to use. If
    pins are on a GPIO device which gets its base GPIO number assigned
    dynamically at run-time, the values can't be hard-coded.
    
    In that case, let the caller tell i2c-mux-gpio the name of the GPIO
    chip and the (relative) GPIO pin numbers to use. At probe time, the
    i2c-mux-gpio driver will look for the chip and apply the proper offset
    to turn relative GPIO pin numbers to absolute GPIO pin numbers.
    
    The same could be (and was so far) done on the caller's end, however
    doing it in i2c-mux-gpio has two benefits:
    * It avoids duplicating the code on every caller's side (about 30
      lines of code.)
    * It allows for deferred probing for the muxed part of the I2C bus
      only. If finding the GPIO chip is the caller's responsibility, then
      deferred probing (if the GPIO chip isn't there yet) will not only
      affect the mux and the I2C bus segments behind it, but also the I2C
      bus trunk.
    Signed-off-by: default avatarJean Delvare <khali@linux-fr.org>
    Cc: Peter Korsgaard <peter.korsgaard@barco.com>
    e7ee5140
i2c-mux-gpio.h 1.35 KB