Re: [PATCH] drm/vc4: remove all usages of of_node_put()

[Amer Al Shanawany <amer.shanawany@gmail.com>]

On 27/04/2024 15.40, Amer Al Shanawany wrote:
> Use the scope-based cleanup feature to clean up 'struct device_node *'
> when they go out of scope, and remove all instances of of_node_put()
> within the same scope, to simplify function exit and avoid potential
> memory leaks.
> 
> Suggested-by: Julia Lawall <julia.lawall@inria.fr>
> Signed-off-by: Amer Al Shanawany <amer.shanawany@gmail.com>
> ---
>   drivers/gpu/drm/vc4/vc4_drv.c  | 14 ++++++--------
>   drivers/gpu/drm/vc4/vc4_hdmi.c |  4 +---
>   drivers/gpu/drm/vc4/vc4_hvs.c  |  4 +---
>   3 files changed, 8 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_drv.c b/drivers/gpu/drm/vc4/vc4_drv.c
> index c133e96b8aca..bb0bb052e595 100644
> --- a/drivers/gpu/drm/vc4/vc4_drv.c
> +++ b/drivers/gpu/drm/vc4/vc4_drv.c
> @@ -289,7 +289,6 @@ static int vc4_drm_bind(struct device *dev)
>   	struct rpi_firmware *firmware = NULL;
>   	struct drm_device *drm;
>   	struct vc4_dev *vc4;
> -	struct device_node *node;
>   	struct drm_crtc *crtc;
>   	bool is_vc5;
>   	int ret = 0;
> @@ -302,11 +301,10 @@ static int vc4_drm_bind(struct device *dev)
>   	else
>   		driver = &vc4_drm_driver;
>   
> -	node = of_find_matching_node_and_match(NULL, vc4_dma_range_matches,
> -					       NULL);
> +	struct device_node *node __free(device_node) =
> +		of_find_matching_node_and_match(NULL, vc4_dma_range_matches, NULL);
>   	if (node) {
>   		ret = of_dma_configure(dev, node, true);
> -		of_node_put(node);
>   
>   		if (ret)
>   			return ret;
> @@ -341,10 +339,10 @@ static int vc4_drm_bind(struct device *dev)
>   			goto err;
>   	}
>   
> -	node = of_find_compatible_node(NULL, NULL, "raspberrypi,bcm2835-firmware");
> -	if (node) {
> -		firmware = rpi_firmware_get(node);
> -		of_node_put(node);
> +	struct device_node *np __free(device_node) =
> +		of_find_compatible_node(NULL, NULL, "raspberrypi,bcm2835-firmware");
> +	if (np) {
> +		firmware = rpi_firmware_get(np);
>   
>   		if (!firmware) {
>   			ret = -EPROBE_DEFER;
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index d30f8e8e8967..915e8da3f41a 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -3661,7 +3661,6 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
>   	struct drm_device *drm = dev_get_drvdata(master);
>   	struct vc4_hdmi *vc4_hdmi;
>   	struct drm_encoder *encoder;
> -	struct device_node *ddc_node;
>   	int ret;
>   
>   	vc4_hdmi = drmm_kzalloc(drm, sizeof(*vc4_hdmi), GFP_KERNEL);
> @@ -3699,14 +3698,13 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
>   	if (ret)
>   		return ret;
>   
> -	ddc_node = of_parse_phandle(dev->of_node, "ddc", 0);
> +	struct device_node *ddc_node __free(device_node) = of_parse_phandle(dev->of_node, "ddc", 0);
>   	if (!ddc_node) {
>   		DRM_ERROR("Failed to find ddc node in device tree\n");
>   		return -ENODEV;
>   	}
>   
>   	vc4_hdmi->ddc = of_find_i2c_adapter_by_node(ddc_node);
> -	of_node_put(ddc_node);
>   	if (!vc4_hdmi->ddc) {
>   		DRM_DEBUG("Failed to get ddc i2c adapter by node\n");
>   		return -EPROBE_DEFER;
> diff --git a/drivers/gpu/drm/vc4/vc4_hvs.c b/drivers/gpu/drm/vc4/vc4_hvs.c
> index 04af672caacb..6e3613e06e09 100644
> --- a/drivers/gpu/drm/vc4/vc4_hvs.c
> +++ b/drivers/gpu/drm/vc4/vc4_hvs.c
> @@ -845,15 +845,13 @@ static int vc4_hvs_bind(struct device *dev, struct device *master, void *data)
>   
>   	if (vc4->is_vc5) {
>   		struct rpi_firmware *firmware;
> -		struct device_node *node;
> +		struct device_node *node __free(device_node) = rpi_firmware_find_node();
>   		unsigned int max_rate;
>   
> -		node = rpi_firmware_find_node();
>   		if (!node)
>   			return -EINVAL;
>   
>   		firmware = rpi_firmware_get(node);
> -		of_node_put(node);
>   		if (!firmware)
>   			return -EPROBE_DEFER;
>   
Hi,

This patch is marked as new/archived on patchwork[1], however it didn't 
receive any feedback, and a similar patch has been already merged [2].


[1]: 
https://patchwork.kernel.org/project/dri-devel/patch/20240427134044.38910-1-amer.shanawany@gmail.com/

[2]: 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d65bfb9546eb627e3c578336355c5b81797f2255

Thank you

Amer