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

[Brian Norris]

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 <briannor...@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