• Milo Kim's avatar
    gpio: add LP3943 I2C GPIO expander driver · 0cc59b9d
    Milo Kim authored
    This is one of LP3943 MFD driver.
    LP3943 is configurable as a GPIO expander, up to 16 GPIOs.
    
    * Application note: how to configure LP3943 as a GPIO expander
      http://www.ti.com/lit/an/snva287a/snva287a.pdf
    
    
    
    * Supported GPIO controller operations
      request, free, direction_input, direction_output, get and set
    
    * GPIO direction register not supported
      LP3943 doesn't have the GPIO direction register. It only provides input and
      output status registers.
      So, private data for the direction should be handled manually.
      This variable is updated whenever the direction is changed and
      used in 'get' operation.
    
    * Pin assignment
      A driver data, 'pin_used' is checked when a GPIO is requested.
      If the GPIO is already assigned, then returns as failure.
      If the GPIO is available, 'pin_used' is set.
      When the GPIO is not used anymore, then it is cleared.
      It is defined as unsigned long type for atomic bit operation APIs,
      but only LSB 16bits are used because LP3943 has 16 outputs.
    
    Signed-off-by: default avatarMilo Kim <milo.kim@ti.com>
    Reviewed-by: default avatarLinus Walleij <linus.walleij@linaro.org>
    Signed-off-by: default avatarLee Jones <lee.jones@linaro.org>
    0cc59b9d