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    • D
      PWM LED driver · de5c9ede
      David Brownell 提交于
      This is a LED driver using the PWM on newer SOCs from Atmel; brightness is
      controlled by changing the PWM duty cycle.  So for example if you've set up
      two leds labeled "pwm0" and "pwm1":
      
      	echo 0 > /sys/class/leds/pwm2/brightness	# off (0%)
      	echo 80 > /sys/class/leds/pwm2/brightness
      	echo 255 > /sys/class/leds/pwm2/brightness	# on (100%)
      
      Note that "brightness" here isn't linear; maybe that should change.  Going
      from 4 to 8 probably doubles perceived brightness, while 244 to 248 is
      imperceptible.
      
      This is mostly intended to be a simple example of PWM, although it's
      realistic since LCD backlights are often driven with PWM to conserve
      battery power (and offer brightness options).
      Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
      Signed-off-by: NHaavard Skinnemoen <hskinnemoen@atmel.com>
      Cc: Richard Purdie <rpurdie@rpsys.net>
      Cc: Andrew Victor <linux@maxim.org.za>
      Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      de5c9ede
  18. 07 2月, 2008 2 次提交