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authorDavid Brownell <david-b@pacbell.net>2008-02-08 13:21:22 +0100
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-08 18:22:38 +0100
commitde5c9edee7a3cfdc6dd1a31c4794dc41ef3c70f9 (patch)
tree2cc474aa124cd9efb8aa5b96072dd3fd2325148b /fs/pipe.c
parentBasic PWM driver for AVR32 and AT91 (diff)
downloadlinux-de5c9edee7a3cfdc6dd1a31c4794dc41ef3c70f9.tar.xz
linux-de5c9edee7a3cfdc6dd1a31c4794dc41ef3c70f9.zip
PWM LED driver
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: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Haavard 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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