Re: [PATCH v5 13/14] video: backlight: lm3533_bl: Implement backlight_scale property

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Race condition in `store_linear` leading to hardware and software state mismatch.
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commit 52a62eb2455ff3beba4492c4d5e3f63ad2e5e71d
Author: Svyatoslav Ryhel <clamor95@gmail.com>
video: backlight: lm3533_bl: Implement backlight_scale property

This commit implements the backlight_scale property for the lm3533_bl driver.
It describes whether the backlight operates in linear or non-linear mode
based on the device state.

> diff --git a/drivers/video/backlight/lm3533_bl.c b/drivers/video/backlight/lm3533_bl.c
> --- a/drivers/video/backlight/lm3533_bl.c
> +++ b/drivers/video/backlight/lm3533_bl.c
> @@ -142,6 +142,7 @@ static ssize_t store_linear(struct device *dev, struct device_attribute *attr,
>  {
>  	struct lm3533_bl *bl = dev_get_drvdata(dev);
>  	int ctrlbank = lm3533_bl_get_ctrlbank_id(bl);
> +	struct backlight_device *bd = bl->bd;
>  	unsigned long linear;
>  	int ret;
>  
> @@ -153,6 +154,9 @@ static ssize_t store_linear(struct device *dev, struct device_attribute *attr,
>  	if (ret)
>  		return ret;
>  
> +	bd->props.scale = linear ? BACKLIGHT_SCALE_LINEAR :
> +				   BACKLIGHT_SCALE_NON_LINEAR;

[Severity: Medium]
Could this allow the hardware state and the software property to diverge
during concurrent writes?

Since kernfs does not serialize concurrent writes to sysfs files, if two
threads write contradictory values at the same time, the regmap updates and
the bd->props.scale updates could interleave. This might result in the
hardware being configured in one mode while bd->props.scale incorrectly
reports the opposite mode.

Would it make sense to protect this update sequence with a lock to ensure both
the hardware and software properties are updated atomically?

> +
>  	return len;
>  }

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Sashiko AI review · https://sashiko.dev/#/patchset/20260617080031.99156-1-clamor95@gmail.com?part=13