[PATCH] drm/panel-edp: take i2c adapter module reference

[PATCH] drm/panel-edp: take i2c adapter module reference

[Johan Hovold]

The i2c subsystem currently blocks during adapter deregistration
whenever there are consumers holding a reference.

Switch to using of_get_i2c_adapter_by_node() which also takes a
reference to the adapter module so that an attempt to unload the module
while in use fails gracefully instead of blocking uninterruptibly.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/gpu/drm/panel/panel-edp.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
index aa27d6cd932e..1606b50513d1 100644
--- a/drivers/gpu/drm/panel/panel-edp.c
+++ b/drivers/gpu/drm/panel/panel-edp.c
@@ -873,7 +873,7 @@ static int panel_edp_probe(struct device *dev, const struct panel_desc *desc,
 
 	ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);
 	if (ddc) {
-		panel->ddc = of_find_i2c_adapter_by_node(ddc);
+		panel->ddc = of_get_i2c_adapter_by_node(ddc);
 		of_node_put(ddc);
 
 		if (!panel->ddc)
@@ -938,7 +938,7 @@ static int panel_edp_probe(struct device *dev, const struct panel_desc *desc,
 	pm_runtime_disable(dev);
 err_finished_ddc_init:
 	if (panel->ddc && (!panel->aux || panel->ddc != &panel->aux->ddc))
-		put_device(&panel->ddc->dev);
+		i2c_put_adapter(panel->ddc);
 
 	return err;
 }
@@ -983,7 +983,7 @@ static void panel_edp_remove(struct device *dev)
 	pm_runtime_dont_use_autosuspend(dev);
 	pm_runtime_disable(dev);
 	if (panel->ddc && (!panel->aux || panel->ddc != &panel->aux->ddc))
-		put_device(&panel->ddc->dev);
+		i2c_put_adapter(panel->ddc);
 
 	drm_edid_free(panel->drm_edid);
 	panel->drm_edid = NULL;
-- 
2.54.0

Re: [PATCH] drm/panel-edp: take i2c adapter module reference

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] When the devicetree's `ddc-i2c-bus` property explicitly points to the DP AUX I2C adapter, the module and device references acquired by `of_get_i2c_adapter_by_node()` are leaked during error cleanup and driver removal.
--

--- Patch [1]: [PATCH] drm/panel-edp: take i2c adapter module reference ---
commit 2c5917c76c861a6fb28736134884b2a3575fb31a
Author: Johan Hovold <johan@kernel.org>

drm/panel-edp: take i2c adapter module reference

The i2c subsystem currently blocks during adapter deregistration
whenever there are consumers holding a reference.

Switch to using of_get_i2c_adapter_by_node() which also takes a
reference to the adapter module so that an attempt to unload the module
while in use fails gracefully instead of blocking uninterruptibly.

> diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
> index f66474d3ef65e..a65bfe50be817 100644
> --- a/drivers/gpu/drm/panel/panel-edp.c
> +++ b/drivers/gpu/drm/panel/panel-edp.c
> @@ -874,7 +874,7 @@ static int panel_edp_probe(struct device *dev, const struct panel_desc *desc,
>  
>  	ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);
>  	if (ddc) {
> -		panel->ddc = of_find_i2c_adapter_by_node(ddc);
> +		panel->ddc = of_get_i2c_adapter_by_node(ddc);
>  		of_node_put(ddc);

[ ... ]

> @@ -939,7 +939,7 @@ static int panel_edp_probe(struct device *dev, const struct panel_desc *desc,
>  	pm_runtime_disable(dev);
>  err_finished_ddc_init:
>  	if (panel->ddc && (!panel->aux || panel->ddc != &panel->aux->ddc))
> -		put_device(&panel->ddc->dev);
> +		i2c_put_adapter(panel->ddc);

[Severity: Medium]
If the devicetree's "ddc-i2c-bus" property explicitly points to the DP AUX I2C
adapter node, panel->ddc will equal &panel->aux->ddc.

While the check panel->ddc != &panel->aux->ddc was already present, switching
to of_get_i2c_adapter_by_node() means a module reference is now acquired here
if the node is parsed from the devicetree.

Does skipping i2c_put_adapter() in this case cause a module reference leak when
an error occurs during probe?

>  
>  	return err;
>  }
> @@ -984,7 +984,7 @@ static void panel_edp_remove(struct device *dev)
>  	pm_runtime_dont_use_autosuspend(dev);
>  	pm_runtime_disable(dev);
>  	if (panel->ddc && (!panel->aux || panel->ddc != &panel->aux->ddc))
> -		put_device(&panel->ddc->dev);
> +		i2c_put_adapter(panel->ddc);

[Severity: Medium]
Similarly, does this skip i2c_put_adapter() and leak the module reference
during driver removal if the devicetree explicitly pointed to the AUX DDC
adapter?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260716132245.1565121-1-johan@kernel.org?part=1

Re: [PATCH] drm/panel-edp: take i2c adapter module reference

[Doug Anderson]

Hi,

On Thu, Jul 16, 2026 at 6:22 AM Johan Hovold <johan@kernel.org> wrote:
>
> The i2c subsystem currently blocks during adapter deregistration
> whenever there are consumers holding a reference.
>
> Switch to using of_get_i2c_adapter_by_node() which also takes a
> reference to the adapter module so that an attempt to unload the module
> while in use fails gracefully instead of blocking uninterruptibly.
>
> Signed-off-by: Johan Hovold <johan@kernel.org>
> ---
>  drivers/gpu/drm/panel/panel-edp.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)

Reviewed-by: Douglas Anderson <dianders@chromium.org>

Worth adding any "Fixes:" tag? I guess this has been using
of_find_i2c_adapter_by_node() for a long time...

Sashiko-bot review [1] seems right, even though it's pointing out
something that isn't really a new problem and is very much a corner
case where someone is crafting an intentionally ridiculous device
tree. If you agree, I wouldn't mind a followup patch fixing that, too.
;-)

[1] https://lore.kernel.org/r/20260716133420.187131F000E9@smtp.kernel.org/