linux-kernel - Re: [PATCH v3 5/5] drm/panel: samsung-s6e88a0-ams427ap24: Add flip option

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Message-ID: <c2c08d39-0be5-42fb-b888-0d4e8db3f85d@rocketmail.com>
Date: Sat, 26 Oct 2024 13:13:01 +0200
From: Jakob Hauser <jahau@...ketmail.com>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Neil Armstrong <neil.armstrong@...aro.org>,
 Jessica Zhang <quic_jesszhan@...cinc.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Thierry Reding <thierry.reding@...il.com>,
 Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
 Andrzej Hajda <andrzej.hajda@...el.com>, dri-devel@...ts.freedesktop.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH v3 5/5] drm/panel: samsung-s6e88a0-ams427ap24: Add flip
 option

Hi Linus,

On 25.10.24 21:32, Linus Walleij wrote:
...
> On Thu, Oct 24, 2024 at 5:18 AM Jakob Hauser <jahau@...ketmail.com> wrote:
> 
>> The way of implementing a flip option follows the existing
>> panel-samsung-s6e8aa0.c [1][2][3].
> 
> That driver is notoriously hard to read because it uses so much
> magic numbers so please don't copy that aspect of the driver.

Actually I used that same approach for the flip option. The 
implementation of flip looked very well to me. I wanted to state it as 
source in the commit message. I don't feel comfortable without declaring it.

> (...)
> 
>> +       if (ctx->flip_horizontal)
>> +               mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xcb, 0x0e);
> 
> #define S6E88A0_SET_FLIP 0xcb
> or something like this.

The 0xcb command register might be more a general panel control, not 
only serving panel flip. But I can't say for sure. Translating single 
commands to command register names becomes too arbitrary.

...

Kind regards,
Jakob