Re: [PATCH v4 2/2] media: i2c: Add Sony IMX908 image sensor driver

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] pm: runtime PM usage counter underflow due to unhandled -EINVAL
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commit 8e82ea0902df5655064466676b372c25f29a3de5
Author: Lachlan Michael <lachlan.michael@sony.com>

media: i2c: Add Sony IMX908 image sensor driver

The IMX908 is an 8.39 MP (3856x2176) CMOS image sensor with a MIPI CSI-2
output interface. The driver supports RAW10 and RAW12 output formats,
exposure and analogue gain controls, image flipping, blanking controls
and test pattern generation.

> diff --git a/drivers/media/i2c/imx908.c b/drivers/media/i2c/imx908.c
> new file mode 100644
> index 0000000000000..4c7e78cfdcc4f
> --- /dev/null
> +++ b/drivers/media/i2c/imx908.c
[ ... ]
> +static int imx908_set_ctrl(struct v4l2_ctrl *ctrl)
> +{
[ ... ]
> +	/* Hardware writes only when powered; cached ctrls applied on resume */
> +	if (IS_ENABLED(CONFIG_PM) && !pm_runtime_get_if_active(imx->dev))
> +		return 0;

[Severity: High]
Does this logic correctly handle errors from pm_runtime_get_if_active()?

The pm_runtime_get_if_active() function returns 1 when the device is
active, 0 when suspended, and a negative error code (like -EINVAL) when
Runtime PM is disabled.

If it returns -EINVAL, the logical NOT operator evaluates to false. This
causes the safety check to be bypassed, allowing the driver to proceed to
execute hardware writes on a potentially unpowered device.

[ ... ]
> +	if (IS_ENABLED(CONFIG_PM))
> +		pm_runtime_put(imx->dev);

[Severity: High]
If the initial pm_runtime_get_if_active() call failed and returned -EINVAL,
does this unmatched pm_runtime_put() cause a usage counter underflow?

Since the initial get call did not increment the usage counter on failure,
executing this put drops the usage counter below its baseline, corrupting
the device's Runtime PM state.

> +
> +	return ret;
> +}

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Sashiko AI review · https://sashiko.dev/#/patchset/20261016075918.19345-1-lachlan.michael@sony.com?part=2