linux-kernel - Re: [PATCH] drm/bridge: ti-sn65dsi86: Implement the pwm

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Date:   Thu, 10 Dec 2020 18:43:38 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Shawn Guo <shawn.guo@...aro.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Thierry Reding <thierry.reding@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Doug Anderson <dianders@...omium.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pwm@...r.kernel.org
Subject: Re: [PATCH] drm/bridge: ti-sn65dsi86: Implement the pwm_chip

On Thu, Dec 10, 2020 at 10:40:36PM +0800, Shawn Guo wrote:
> Hi Uwe,
> 
> On Thu, Dec 10, 2020 at 9:05 PM Uwe Kleine-König
> <u.kleine-koenig@...gutronix.de> wrote:
> > > > @@ -111,6 +118,8 @@
> > > >
> > > >  #define SN_LINK_TRAINING_TRIES             10
> > > >
> > > > +#define SN_PWM_GPIO                        3
> > >
> > > So this maps to the GPIO4 described in sn65dsi86 datasheet.  I'm
> > > wondering if it's more readable to define the following SHIFT constants
> > > (your code), and use GPIO_MUX_GPIO4_SHIFT >> 2 where you need GPIO
> > > offset?
> > >
> > > #define  GPIO_MUX_GPIO1_SHIFT 0
> > > #define  GPIO_MUX_GPIO2_SHIFT 2
> > > #define  GPIO_MUX_GPIO3_SHIFT 4
> > > #define  GPIO_MUX_GPIO4_SHIFT 6
> > >
> > > If you agree, you may consider to integrate this patch beforehand:
> > >
> > > https://github.com/shawnguo2/linux/commit/7cde887ffb3b27a36e77a08bee3666d14968b586
> >
> > My preferred way here would be to add a prefix for the other constants.
> > It (IMHO) looks nicer and
> >
> >         GPIO_INPUT_SHIFT
> >
> > looks like a quite generic name for a hardware specific definition.
> 
> While this looks like a reasonable argument, I also like the naming
> choice for these constants in the beginning for that distinction
> between registers and bits.  And changing the names the other way
> around means there will be a much bigger diffstat, which I would like
> to avoid.  I suggest let's just focus on what really matters here -
> keep the naming consistent, so that people do not get confused when
> they want to add more constants in there.

In my eyes the bigger diffstat is justified. As I wrote,
GPIO_INPUT_SHIFT isn't used in other files, but please look how many
definitions there are for RESET. The usefulness of ctags/cscope is quite
reduced if generic terms are used this way.

Best regards
Uwe

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

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