1. 07 May, 2014 1 commit
    • Alexandre Courbot's avatar
      pwm-backlight: switch to gpiod interface · 257462db
      Alexandre Courbot authored
      Switch to the new gpiod interface, which allows to handle GPIO
      properties such as active low transparently and removes a whole bunch of
      code.
      
      There are still a couple of users of this driver that rely on passing
      the enable GPIO number through platform data, so a fallback mechanism
      using a GPIO number is still available to avoid breaking them. It will
      be removed once current users have switched to the GPIO lookup tables
      provided by the gpiod interface.
      Signed-off-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
      Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
      257462db
  2. 16 Oct, 2013 1 commit
    • Thierry Reding's avatar
      pwm-backlight: Add optional enable GPIO · 2b9b1620
      Thierry Reding authored
      To support a wider variety of backlight setups, introduce an optional
      enable GPIO. Legacy users of the platform data already have a means of
      supporting GPIOs by using the .init(), .exit() and .notify() hooks. DT
      users however cannot use those, so an alternative method is required.
      
      In order to ease the introduction of the optional enable GPIO, make it
      available in the platform data first, so that existing users can be
      converted. Once that has happened a second patch will add code to make
      use of it in the driver.
      Signed-off-by: default avatarThierry Reding <treding@nvidia.com>
      2b9b1620
  3. 23 Jul, 2012 1 commit
  4. 25 Aug, 2011 1 commit
  5. 23 Mar, 2011 1 commit
    • Robert Morell's avatar
      pwm_backlight: add check_fb() hook · ef0a5e80
      Robert Morell authored
      In systems with multiple framebuffer devices, one of the devices might be
      blanked while another is unblanked.  In order for the backlight blanking
      logic to know whether to turn off the backlight for a particular
      framebuffer's blanking notification, it needs to be able to check if a
      given framebuffer device corresponds to the backlight.
      
      This plumbs the check_fb hook from core backlight through the
      pwm_backlight helper to allow platform code to plug in a check_fb hook.
      Signed-off-by: default avatarRobert Morell <rmorell@nvidia.com>
      Cc: Richard Purdie <rpurdie@rpsys.net>
      Cc: Arun Murthy <arun.murthy@stericsson.com>
      Cc: Linus Walleij <linus.walleij@stericsson.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ef0a5e80
  6. 12 Nov, 2010 1 commit
    • Arun Murthy's avatar
      backlight: add low threshold to pwm backlight · fef7764f
      Arun Murthy authored
      The intensity of the backlight can be varied from a range of
      max_brightness to zero.  Though most, if not all the pwm based backlight
      devices start flickering at lower brightness value.  And also for each
      device there exists a brightness value below which the backlight appears
      to be turned off though the value is not equal to zero.
      
      If the range of brightness for a device is from zero to max_brightness.  A
      graph is plotted for brightness Vs intensity for the pwm based backlight
      device has to be a linear graph.
      
      intensity
      	  |   /
      	  |  /
      	  | /
      	  |/
      	  ---------
      	 0	max_brightness
      
      But pratically on measuring the above we note that the intensity of
      backlight goes to zero(OFF) when the value in not zero almost nearing to
      zero(some x%).  so the graph looks like
      
      intensity
      	  |    /
      	  |   /
      	  |  /
      	  |  |
      	  ------------
      	 0   x	 max_brightness
      
      In order to overcome this drawback knowing this x% i.e nothing but the low
      threshold beyond which the backlight is off and will have no effect, the
      brightness value is being offset by the low threshold value(retaining the
      linearity of the graph).  Now the graph becomes
      
      intensity
      	  |     /
      	  |    /
      	  |   /
      	  |  /
      	  -------------
      	   0	  max_brightness
      
      With this for each and every digit increment in the brightness from zero
      there is a change in the intensity of backlight.  Devices having this
      behaviour can set the low threshold brightness(lth_brightness) and pass
      the same as platform data else can have it as zero.
      
      [akpm@linux-foundation.org: coding-style fixes]
      Signed-off-by: default avatarArun Murthy <arun.murthy@stericsson.com>
      Acked-by: default avatarLinus Walleij <linus.walleij@stericsson.com>
      Acked-by: default avatarRichard Purdie <rpurdie@linux.intel.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      fef7764f
  7. 17 Dec, 2009 1 commit
  8. 03 Jul, 2008 2 commits