linux-kernel - Re: [PATCH 2/2] drm/panel: add BOE tv101wum-ll2 panel driver

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Message-ID: <e3dee615-1df5-400c-82a3-3baff08c66bf@linaro.org>
Date: Wed, 28 Aug 2024 11:02:05 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Doug Anderson <dianders@...omium.org>
Cc: Jessica Zhang <quic_jesszhan@...cinc.com>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, dri-devel@...ts.freedesktop.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] drm/panel: add BOE tv101wum-ll2 panel driver

On 24/07/2024 09:50, Neil Armstrong wrote:
> On 23/07/2024 21:17, Doug Anderson wrote:
>> Hi,
>>
>> On Tue, Jul 9, 2024 at 6:06 AM Neil Armstrong <neil.armstrong@...aro.org> wrote:
>>>

<snip>

>>
>>> +static int boe_tv101wum_ll2_get_modes(struct drm_panel *panel,
>>> +                                     struct drm_connector *connector)
>>> +{
>>> +       return drm_connector_helper_get_modes_fixed(connector, &boe_tv101wum_ll2_mode);
>>
>> Random question for you: on panels that don't use the
>> drm_connector_helper the "bpc" gets set here. Is there a reason why
>> some panel drivers (like this one) don't set bpc?
> 
> Good question, I'll check

Ok so the documentation says :
https://elixir.bootlin.com/linux/v6.11-rc5/source/include/drm/drm_connector.h#L698
	 * @bpc: Maximum bits per color channel. Used by HDMI and DP outputs.

and looking at the code, all drivers considers bpc=8 when unset.

but yeah ultimately drm_connector_helper_get_modes_fixed should have a variant to set the bpc
when != 8.

In this case it's useless.

Neil


<snip>