Re: [PATCH v4 07/20] drm/bridge: inno-hdmi: Split probe out of bind

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Medium] drm/bridge: inno-hdmi: Meaningful code and commit message mismatch for inno_hdmi_remove()
- [Medium] drm/bridge: inno-hdmi: TOCTOU race on hdmi->bridge.dev leading to potential NULL pointer dereference
--

commit 619d70bf74f8f0e498489e8aa8a7c0c9e4e2d3fb
Author: Michal Wilczynski <m.wilczynski@samsung.com>

drm/bridge: inno-hdmi: Split probe out of bind

This commit splits the bridge setup into a new exported inno_hdmi_probe()
function and reduces inno_hdmi_bind() to a wrapper around it. This
decoupling allows a platform device to register its own bridge without
attaching it to the DRM encoder immediately.

>     Move the setup into a new exported inno_hdmi_probe(), with a matching
>     inno_hdmi_remove(), and reduce inno_hdmi_bind() to a wrapper around it.

[Severity: Medium]
Is the commit message description accurate regarding the removal function?

The commit message explicitly claims to introduce a matching
inno_hdmi_remove() function for teardown alongside inno_hdmi_probe(), but
this function appears to be missing from the patch. Does this break the
expected API contract described for external decoupled drivers?

> diff --git a/drivers/gpu/drm/bridge/inno-hdmi.c b/drivers/gpu/drm/bridge/inno-hdmi.c
> index dd35f5a875d3d..840f1c7bc2029 100644
> --- a/drivers/gpu/drm/bridge/inno-hdmi.c
> +++ b/drivers/gpu/drm/bridge/inno-hdmi.c
> @@ -929,7 +929,14 @@ static irqreturn_t inno_hdmi_irq(int irq, void *dev_id)
>  {
>  	struct inno_hdmi *hdmi = dev_id;
>  
> -	drm_helper_hpd_irq_event(hdmi->bridge.dev);
> +	/*
> +	 * The interrupt is requested in probe, but bridge.dev is only set once
> +	 * the DRM master binds and attaches the bridge, which may never happen.
> +	 * Drop hotplug events that arrive before then rather than dereference a
> +	 * NULL drm_device.
> +	 */
> +	if (hdmi->bridge.dev)
> +		drm_helper_hpd_irq_event(hdmi->bridge.dev);

[Severity: Medium]
Can this lockless check of hdmi->bridge.dev lead to a NULL pointer
dereference?

Without READ_ONCE(), the compiler might double-fetch the pointer. If the
pointer is cleared concurrently (for example, during a failed
drm_bridge_attach() or a teardown path) after the check but before it is
passed to drm_helper_hpd_irq_event(), it could result in a NULL pointer
dereference.

Could we use READ_ONCE() and a local variable to prevent a potential race
condition in inno_hdmi_irq()?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260915-jh7110-clean-send-v4-0-f0e4fd6f2cc8@samsung.com?part=7