Re: [PATCH v4 4/6] dt-bindings: display: stm32-ltdc: add optional st,fb-bpp property

From: Conor Dooley <conor@kernel.org>
To: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Cc: linux-kernel@vger.kernel.org,
	Philippe Cornu <philippe.cornu@foss.st.com>,
	Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>,
	Amarula patchwork <linux-amarula@amarulasolutions.com>,
	michael@amarulasolutions.com,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Conor Dooley <conor+dt@kernel.org>,
	Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@gmail.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Rob Herring <robh+dt@kernel.org>,
	Yannick Fertre <yannick.fertre@foss.st.com>,
	devicetree@vger.kernel.org, dri-devel@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org,
	linux-stm32@st-md-mailman.stormreply.com
Subject: Re: [PATCH v4 4/6] dt-bindings: display: stm32-ltdc: add optional st,fb-bpp property
Date: Mon, 19 Jun 2023 21:18:25 +0100	[thread overview]
Message-ID: <20230619-ion-decree-c63d2eb11e83@spud> (raw)
In-Reply-To: <20230619165525.1035243-5-dario.binacchi@amarulasolutions.com>

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Hey,

On Mon, Jun 19, 2023 at 06:55:23PM +0200, Dario Binacchi wrote:
> Boards that use the STM32F{4,7} series have limited amounts of RAM. The
> added property allows to size, within certain limits, the memory footprint
> required by the framebuffer.

Hmm, this sounds quite a lot like "software policy", since the actual
display doesn't have these limitations. Rob, Krzysztof?

> 
> Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
> ---
> 
> (no changes since v1)

Really?
https://lore.kernel.org/all/?q=dfn:st,stm32-ltdc.yaml%20

You sure this shouldn't be "new in v4"?

>  .../devicetree/bindings/display/st,stm32-ltdc.yaml          | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/st,stm32-ltdc.yaml b/Documentation/devicetree/bindings/display/st,stm32-ltdc.yaml
> index d6ea4d62a2cf..1c3a3653579f 100644
> --- a/Documentation/devicetree/bindings/display/st,stm32-ltdc.yaml
> +++ b/Documentation/devicetree/bindings/display/st,stm32-ltdc.yaml
> @@ -42,6 +42,12 @@ properties:
>        - for internal dpi input of the MIPI DSI host controller.
>        Note: These 2 endpoints cannot be activated simultaneously.
>  
> +  st,fb-bpp:

Is there not a more understandable property name than this?
Maybe I just had to think about it because fbdev stuff aint something
I've worked with...

> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +      bit depth of framebuffer (8, 16 or 32)
> +    maxItems: 1

Why not make it an enum, since there are only 4 values?

Cheers,
Conor.

> +
>  required:
>    - compatible
>    - reg
> -- 
> 2.32.0
> 

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