On Fri, 27 May 2016 09:35:33 -0700 Brian Norris <[email protected]> wrote:
> Hi Boris, > > On Fri, May 27, 2016 at 09:34:39AM +0200, Boris Brezillon wrote: > > On Thu, 26 May 2016 14:05:30 -0700 > > Brian Norris <[email protected]> wrote: > > > > > 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 <[email protected]> > > > --- > > > 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; > > > + > > > > Argh, I forgot to move the pwm_config() checks [1] into > > pwm_apply_state() :-/. > > Oh, I didn't actually notice this was a regression. > > > I think we should check all the corner cases (see this diff [2]), > > Now that you mention it, I think you've also dropped some signed > (negative value) checking in pwm_config(). I'll squash in your diff + > some pwm_config() fixes. ->period and ->duty_cycle are unsigned now ;). -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
