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[PATCH] pwm: don't allow duty cycle higher than period

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It doesn't make sense to allow the duty cycle to be larger than the
period. I can see this behavior by, e.g.:

  # echo 1 > /sys/class/pwm/pwmchip0/export
  # cat /sys/class/pwm/pwmchip0/pwm1/period
  100
  # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
  [... driver may or may not reject the value, or trigger some logic bug ...]

It's better to see:

  # echo 1 > /sys/class/pwm/pwmchip0/export
  # cat /sys/class/pwm/pwmchip0/pwm1/period
  100
  # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
  -bash: echo: write error: Invalid argument

Signed-off-by: Brian Norris <briannorris@chromium.org>
---
 drivers/pwm/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index dba3843c53b8..9246b60f894a 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -463,6 +463,9 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
 	if (!memcmp(state, &pwm->state, sizeof(*state)))
 		return 0;
 
+	if (state->duty_cycle > state->period)
+		return -EINVAL;
+
 	if (pwm->chip->ops->apply) {
 		err = pwm->chip->ops->apply(pwm->chip, pwm, state);
 		if (err)
-- 
2.8.0.rc3.226.g39d4020

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[PATCH] pwm: don't allow duty cycle higher than period Brian Norris <briannorris@chromium.org> - 2016-05-26 23:10 +0200
  Re: [PATCH] pwm: don't allow duty cycle higher than period Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-05-27 09:40 +0200
    Re: [PATCH] pwm: don't allow duty cycle higher than period Brian Norris <briannorris@chromium.org> - 2016-05-27 18:40 +0200
      Re: [PATCH] pwm: don't allow duty cycle higher than period Brian Norris <briannorris@chromium.org> - 2016-05-27 19:00 +0200
    Re: [PATCH] pwm: don't allow duty cycle higher than period Brian Norris <briannorris@chromium.org> - 2016-05-27 18:40 +0200
      Re: [PATCH] pwm: don't allow duty cycle higher than period Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-05-27 18:40 +0200
        Re: [PATCH] pwm: don't allow duty cycle higher than period Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-05-27 18:50 +0200

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