[PATCH] drm: bridge: adv7511: Add check for mipi_dsi_driver_register

[PATCH] drm: bridge: adv7511: Add check for mipi_dsi_driver_register

[Jiasheng Jiang]

As mipi_dsi_driver_register could return error if fails,
it should be better to check the return value and return error
if fails.

Fixes: 1e4d58cd7f88 ("drm/bridge: adv7533: Create a MIPI DSI device")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
---
 drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
index 5bb9300040dd..795855b41eb2 100644
--- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
+++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
@@ -1392,8 +1392,13 @@ static struct i2c_driver adv7511_driver = {
 
 static int __init adv7511_init(void)
 {
-	if (IS_ENABLED(CONFIG_DRM_MIPI_DSI))
-		mipi_dsi_driver_register(&adv7533_dsi_driver);
+	int ret;
+
+	if (IS_ENABLED(CONFIG_DRM_MIPI_DSI)) {
+		ret = mipi_dsi_driver_register(&adv7533_dsi_driver);
+		if (ret)
+			return ret;
+	}
 
 	return i2c_add_driver(&adv7511_driver);
 }
-- 
2.25.1

Re: [PATCH] drm: bridge: adv7511: Add check for mipi_dsi_driver_register

[Laurent Pinchart]

Hi Jiasheng,

Thank you for the patch.

On Wed, Jun 01, 2022 at 10:48:22AM +0800, Jiasheng Jiang wrote:
> As mipi_dsi_driver_register could return error if fails,
> it should be better to check the return value and return error
> if fails.
> 
> Fixes: 1e4d58cd7f88 ("drm/bridge: adv7533: Create a MIPI DSI device")
> Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
> ---
>  drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> index 5bb9300040dd..795855b41eb2 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> @@ -1392,8 +1392,13 @@ static struct i2c_driver adv7511_driver = {
>  
>  static int __init adv7511_init(void)
>  {
> -	if (IS_ENABLED(CONFIG_DRM_MIPI_DSI))
> -		mipi_dsi_driver_register(&adv7533_dsi_driver);
> +	int ret;
> +
> +	if (IS_ENABLED(CONFIG_DRM_MIPI_DSI)) {
> +		ret = mipi_dsi_driver_register(&adv7533_dsi_driver);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	return i2c_add_driver(&adv7511_driver);

While at it, should this then call mipi_dsi_driver_unregister() on
failure ?

>  }
> -- 
> 2.25.1
> 

-- 
Regards,

Laurent Pinchart

Re: Re: [PATCH] drm: bridge: adv7511: Add check for mipi_dsi_driver_register

[Jiasheng Jiang]

On Wed, Jun 01, 2022 at 05:15:37PM +0800, Laurent Pinchart wrote:
>> Well, as far as I am concerned, the adv7511_exit() in the same file has already dealt with the issue.
>> Therefore, it might not be necessary to add another mipi_dsi_driver_unregister().
> 
> The issue is that adv7511_exit() is not called if adv7511_init() fails.

Sorry, I can not find the caller of adv7511_init().
Please give me more detail.

Thanks,
Jiang

Re: [PATCH] drm: bridge: adv7511: Add check for mipi_dsi_driver_register

[Maxime Ripard]

On Wed, Jun 01, 2022 at 07:12:55PM +0800, Jiasheng Jiang wrote:
> On Wed, Jun 01, 2022 at 05:15:37PM +0800, Laurent Pinchart wrote:
> >> Well, as far as I am concerned, the adv7511_exit() in the same file has already dealt with the issue.
> >> Therefore, it might not be necessary to add another mipi_dsi_driver_unregister().
> > 
> > The issue is that adv7511_exit() is not called if adv7511_init() fails.
> 
> Sorry, I can not find the caller of adv7511_init().
> Please give me more detail.

It's called by the kernel when the module is unloaded (module_exit).
It's not what Laurent is saying though.

His point is that in adv7511, if i2c_add_driver fails, you'll still need
to call mipi_dsi_driver_unregister to clean things up.

Maxime