linux-kernel - Re: [PATCH] pwm: pca9685: fix pwm/gpio inter-operation

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Message-ID: <20190604144728.GY2781@lahna.fi.intel.com>
Date:   Tue, 4 Jun 2019 17:47:28 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Sven Van Asbroeck <thesven73@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        linux-pwm@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        YueHaibing <yuehaibing@...wei.com>
Subject: Re: [PATCH] pwm: pca9685: fix pwm/gpio inter-operation

On Tue, Jun 04, 2019 at 09:34:46AM -0400, Sven Van Asbroeck wrote:
> Thank you for the review, Mika ! See comments below.
> 
> On Tue, Jun 4, 2019 at 5:14 AM Mika Westerberg
> <mika.westerberg@...ux.intel.com> wrote:
> >
> > > This approach will also prevent the request of the "all" pwm channel, if any
> > > other pwm channel is already in use. Is this correct behaviour?
> >
> > Sounds correct to me.
> 
> Something that occurred to me right after I pressed the send button:
> 
> This patch will prevent a pwm 'all channels' request if at least one
> of the pwm's is in use. But it will not guard against the opposite:
> after the 'all channels' pwm is requested, it will still allow requests
> for other pwms/gpios !
> 
> This is identical to the old behaviour. But maybe this is an oversight
> and not a feature?

Most probably an oversight.

> Proposal:
> 1. prevent request of 'all channel' if any of the pwms/gpios are in use
> 2. prevent request of all other pwms/gpios if 'all channels' is in use

Makes sense.