From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brian Norris Subject: Re: [PATCH] pwm: don't allow duty cycle higher than period Date: Fri, 27 May 2016 09:35:33 -0700 Message-ID: <20160527163533.GA80118@google.com> References: <1464296730-121773-1-git-send-email-briannorris@chromium.org> <20160527093439.5ad237c5@bbrezillon> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-pf0-f171.google.com ([209.85.192.171]:34376 "EHLO mail-pf0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753336AbcE0Qfi (ORCPT ); Fri, 27 May 2016 12:35:38 -0400 Received: by mail-pf0-f171.google.com with SMTP id y69so43219381pfb.1 for ; Fri, 27 May 2016 09:35:38 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20160527093439.5ad237c5@bbrezillon> Sender: linux-pwm-owner@vger.kernel.org List-Id: linux-pwm@vger.kernel.org To: Boris Brezillon Cc: Thierry Reding , linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org, Brian Norris , Doug Anderson 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 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() :-/. 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. > once done you can add my > > Acked-by: Boris Brezillon I'll send v2 without your ack, since I'm going to add a tiny bit extra. That'll give you a chance to ack the final (?) version. > Thierry, can you include that in your material for 4.7-rc1? That sounds like it would be a good idea, IMO. Thanks for noticing this was a regression! :) Regards, Brian > 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