linux-kernel - Re: [PATCH 3/5] gpu: drm: adp: Add a backlight driver for the Summit LCD

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Message-ID: <3a6fb7fd-eb3d-428b-a37c-f04d81e7fbd0@gmail.com>
Date: Mon, 25 Nov 2024 23:03:11 +0800
From: Nick Chan <towinchenmi@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, fnkl.kernel@...il.com,
 Hector Martin <marcan@...can.st>, Sven Peter <sven@...npeter.dev>,
 Alyssa Rosenzweig <alyssa@...enzweig.io>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Neil Armstrong <neil.armstrong@...aro.org>,
 Jessica Zhang <quic_jesszhan@...cinc.com>, asahi@...ts.linux.dev
Cc: linux-arm-kernel@...ts.infradead.org, dri-devel@...ts.freedesktop.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] gpu: drm: adp: Add a backlight driver for the Summit
 LCD



Krzysztof Kozlowski 於 2024/11/25 晚上10:49 寫道:
> On 24/11/2024 23:29, Sasha Finkelstein via B4 Relay wrote:
>> From: Sasha Finkelstein <fnkl.kernel@...il.com>
>>
>> This is the display panel used for the touchbar on laptops that have it.
> 
> 
> ...
> 
> 
>> +static int summit_probe(struct mipi_dsi_device *dsi)
>> +{
>> +	struct backlight_properties props = { 0 };
>> +	struct device *dev = &dsi->dev;
>> +	struct summit_data *panel;
>> +
>> +	panel = devm_kzalloc(dev, sizeof(*panel), GFP_KERNEL);
>> +	if (!panel)
>> +		return -ENOMEM;
>> +
>> +	mipi_dsi_set_drvdata(dsi, panel);
>> +	panel->dsi = dsi;
>> +
>> +	int ret = device_property_read_u32(dev, "max-brightness", &props.max_brightness);
> That's an undocumented property, which suggests you did not test your DTS.

Actually, testing the DTS would not have caught this issue. For more
context,
all summit panels found in touch bar have a max brightness of 255, but the
summit panel in Apple A11 devices like the iPhone X is latter found to have
a max brightness of 2047.

However, A11 cannot be properly supported right now due to not having a
driver
for the DART IOMMU.

In the meantime, max-brightness could documented and be made required,
and the
default 255 brightness could be removed.

> 
> It does not look like you tested the DTS against bindings. Please run
> `make dtbs_check W=1` (see
> Documentation/devicetree/bindings/writing-schema.rst or
> https://www.linaro.org/blog/tips-and-tricks-for-validating-devicetree-sources-with-the-devicetree-schema/
> for instructions).
> 
> Best regards,
> Krzysztof

Nick Chan