Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Sat, 23 May 2020 22:01:25 +0200
From:   Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= 
        <u.kleine-koenig@pengutronix.de>
To:     David Wu <david.wu@rock-chips.com>
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        Heiko Stuebner <heiko@sntech.de>, linux-pwm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>
Subject: Re: [PATCH] pwm: rockchip: simplify rockchip_pwm_get_state()
Message-ID: <20200523200125.khdw3eau5eakxqy6@pengutronix.de>
References: <20190919091728.24756-1-linux@rasmusvillemoes.dk>
 <20190919111115.5oraof2bdl4627xv@pengutronix.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20190919111115.5oraof2bdl4627xv@pengutronix.de>
User-Agent: NeoMutt/20170113 (1.7.2)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hello David,

On Thu, Sep 19, 2019 at 01:11:15PM +0200, oUwe Kleine-K?nig wrote:
> On Thu, Sep 19, 2019 at 11:17:27AM +0200, Rasmus Villemoes wrote:
> > The way state->enabled is computed is rather convoluted and hard to
> > read - both branches of the if() actually do the exact same thing. So
> > remove the if(), and further simplify "<boolean condition> ? true :
> > false" to "<boolean condition>".
> > 
> > Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> > ---
> > I stumbled on this while trying to understand how the pwm subsystem
> > works. This patch is a semantic no-op, but it's also possible that,
> > say, the first branch simply contains a "double negative" so either
> > the != should be == or the "false : true" should be "true : false".
> 
> The change looks obviously right, it's a noop.
> 
> I share your doubts however. The construct was introduced in commit 
> 831b2790507b ("pwm: rockchip: Use same PWM ops for each IP") by David
> Wu.
> 
> Before there were rockchip_pwm_get_state_v1 for the supports_polarity =
> false case and rockchip_pwm_get_state_v2 for supports_polarity = true.
> 
> In both state->enabled was assigned true if ((val & enable_conf) ==
> enable_conf). So I assume everything is fine.
> 
> A confirmation by David would be great though.

This is still open. Can you please have a look at
https://patchwork.ozlabs.org/project/linux-pwm/patch/20190919091728.24756-1-linux@rasmusvillemoes.dk/
and verify it's correct?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |