From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Brezillon Subject: Re: [PATCH] pwm: don't allow duty cycle higher than period Date: Fri, 27 May 2016 09:34:39 +0200 Message-ID: <20160527093439.5ad237c5@bbrezillon> References: <1464296730-121773-1-git-send-email-briannorris@chromium.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from down.free-electrons.com ([37.187.137.238]:48089 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751451AbcE0Hem (ORCPT ); Fri, 27 May 2016 03:34:42 -0400 In-Reply-To: <1464296730-121773-1-git-send-email-briannorris@chromium.org> Sender: linux-pwm-owner@vger.kernel.org List-Id: linux-pwm@vger.kernel.org To: Brian Norris Cc: Thierry Reding , linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org, Brian Norris , Doug Anderson Hi Brian, On Thu, 26 May 2016 14:05:30 -0700 Brian Norris 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 > --- > 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() :-/. I think we should check all the corner cases (see this diff [2]), once done you can add my Acked-by: Boris Brezillon Thierry, can you include that in your material for 4.7-rc1? Thanks, Boris [1]http://lxr.free-electrons.com/source/drivers/pwm/core.c#L443 [2]http://code.bulix.org/wtqja4-99473 -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com