[v1] drm/bridge: analogix_dp: Fix bailout for devm_drm_bridge_alloc()

[PATCH] drm/bridge: analogix_dp: Fix bailout for devm_drm_bridge_alloc()

Posted by Liu Ying 1 month, 4 weeks ago

devm_drm_bridge_alloc() returns ERR_PTR on failure instead of a
NULL pointer, so use IS_ERR() to check the returned pointer.

Fixes: 48f05c3b4b70 ("drm/bridge: analogix_dp: Use devm_drm_bridge_alloc() API")
Signed-off-by: Liu Ying <victor.liu@nxp.com>
---
 drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index ed35e567d117..86cf898a09bb 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1474,7 +1474,7 @@ analogix_dp_probe(struct device *dev, struct analogix_dp_plat_data *plat_data)
 
 	dp = devm_drm_bridge_alloc(dev, struct analogix_dp_device, bridge,
 				   &analogix_dp_bridge_funcs);
-	if (!dp)
+	if (IS_ERR(dp))
 		return ERR_PTR(-ENOMEM);
 
 	dp->dev = &pdev->dev;
-- 
2.34.1

Re: [PATCH] drm/bridge: analogix_dp: Fix bailout for devm_drm_bridge_alloc()

Posted by Luca Ceresoli 1 month, 4 weeks ago

Hello Liu,

On Wed,  6 Aug 2025 16:54:24 +0800
Liu Ying <victor.liu@nxp.com> wrote:

> devm_drm_bridge_alloc() returns ERR_PTR on failure instead of a
> NULL pointer, so use IS_ERR() to check the returned pointer.
> 
> Fixes: 48f05c3b4b70 ("drm/bridge: analogix_dp: Use devm_drm_bridge_alloc() API")
> Signed-off-by: Liu Ying <victor.liu@nxp.com>
> ---
>  drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> index ed35e567d117..86cf898a09bb 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> @@ -1474,7 +1474,7 @@ analogix_dp_probe(struct device *dev, struct analogix_dp_plat_data *plat_data)
>  
>  	dp = devm_drm_bridge_alloc(dev, struct analogix_dp_device, bridge,
>  				   &analogix_dp_bridge_funcs);
> -	if (!dp)
> +	if (IS_ERR(dp))
>  		return ERR_PTR(-ENOMEM);

Good catch, thanks!

You fix is correct but now I realized one additional fix is needed in
the following line:

-		return ERR_PTR(-ENOMEM);
+		return ERR_PTR(dp);

Can you send a v2 with that fixed?

Luca

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH] drm/bridge: analogix_dp: Fix bailout for devm_drm_bridge_alloc()

Posted by Liu Ying 1 month, 4 weeks ago

On 08/06/2025, Luca Ceresoli wrote:
> Hello Liu,
> 
> On Wed,  6 Aug 2025 16:54:24 +0800
> Liu Ying <victor.liu@nxp.com> wrote:
> 
>> devm_drm_bridge_alloc() returns ERR_PTR on failure instead of a
>> NULL pointer, so use IS_ERR() to check the returned pointer.
>>
>> Fixes: 48f05c3b4b70 ("drm/bridge: analogix_dp: Use devm_drm_bridge_alloc() API")
>> Signed-off-by: Liu Ying <victor.liu@nxp.com>
>> ---
>>  drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> index ed35e567d117..86cf898a09bb 100644
>> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> @@ -1474,7 +1474,7 @@ analogix_dp_probe(struct device *dev, struct analogix_dp_plat_data *plat_data)
>>  
>>  	dp = devm_drm_bridge_alloc(dev, struct analogix_dp_device, bridge,
>>  				   &analogix_dp_bridge_funcs);
>> -	if (!dp)
>> +	if (IS_ERR(dp))
>>  		return ERR_PTR(-ENOMEM);
> 
> Good catch, thanks!
> 
> You fix is correct but now I realized one additional fix is needed in
> the following line:
> 
> -		return ERR_PTR(-ENOMEM);
> +		return ERR_PTR(dp);

You mean ERR_CAST(dp)?

> 
> Can you send a v2 with that fixed?

I find devm_drm_bridge_alloc() always returns ERR_PTR(-ENOMEM) in this
driver context, so it seems fine to keep the existing ERR_PTR(-ENOMEM).
If you prefer ERR_CAST(dp), I may send v2 to use ERR_CAST(dp).

> 
> Luca
> 


-- 
Regards,
Liu Ying

Re: [PATCH] drm/bridge: analogix_dp: Fix bailout for devm_drm_bridge_alloc()

Posted by Luca Ceresoli 1 month, 4 weeks ago

On Wed, 6 Aug 2025 17:38:17 +0800
Liu Ying <victor.liu@nxp.com> wrote:

> On 08/06/2025, Luca Ceresoli wrote:
> > Hello Liu,
> > 
> > On Wed,  6 Aug 2025 16:54:24 +0800
> > Liu Ying <victor.liu@nxp.com> wrote:
> >   
> >> devm_drm_bridge_alloc() returns ERR_PTR on failure instead of a
> >> NULL pointer, so use IS_ERR() to check the returned pointer.
> >>
> >> Fixes: 48f05c3b4b70 ("drm/bridge: analogix_dp: Use devm_drm_bridge_alloc() API")
> >> Signed-off-by: Liu Ying <victor.liu@nxp.com>
> >> ---
> >>  drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> >> index ed35e567d117..86cf898a09bb 100644
> >> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> >> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> >> @@ -1474,7 +1474,7 @@ analogix_dp_probe(struct device *dev, struct analogix_dp_plat_data *plat_data)
> >>  
> >>  	dp = devm_drm_bridge_alloc(dev, struct analogix_dp_device, bridge,
> >>  				   &analogix_dp_bridge_funcs);
> >> -	if (!dp)
> >> +	if (IS_ERR(dp))
> >>  		return ERR_PTR(-ENOMEM);  
> > 
> > Good catch, thanks!
> > 
> > You fix is correct but now I realized one additional fix is needed in
> > the following line:
> > 
> > -		return ERR_PTR(-ENOMEM);
> > +		return ERR_PTR(dp);  
> 
> You mean ERR_CAST(dp)?

Ah, indeed!

> > Can you send a v2 with that fixed?  
> 
> I find devm_drm_bridge_alloc() always returns ERR_PTR(-ENOMEM) in this
> driver context, so it seems fine to keep the existing ERR_PTR(-ENOMEM).
> If you prefer ERR_CAST(dp), I may send v2 to use ERR_CAST(dp).

The documentation says:

 * Returns:                  
 * Pointer to new bridge, or ERR_PTR on failure.

So let's follow that, which is a (relatively) immutable contract, and
not the implementation which might change over time.

This is also what all callers of devm_drm_bridge_alloc() do, unless I
missed something.

Thanks,
Luca

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH] drm/bridge: analogix_dp: Fix bailout for devm_drm_bridge_alloc()

Posted by Liu Ying 1 month, 4 weeks ago

On 08/06/2025, Luca Ceresoli wrote:
> On Wed, 6 Aug 2025 17:38:17 +0800
> Liu Ying <victor.liu@nxp.com> wrote:
> 
>> On 08/06/2025, Luca Ceresoli wrote:
>>> Hello Liu,
>>>
>>> On Wed,  6 Aug 2025 16:54:24 +0800
>>> Liu Ying <victor.liu@nxp.com> wrote:
>>>   
>>>> devm_drm_bridge_alloc() returns ERR_PTR on failure instead of a
>>>> NULL pointer, so use IS_ERR() to check the returned pointer.
>>>>
>>>> Fixes: 48f05c3b4b70 ("drm/bridge: analogix_dp: Use devm_drm_bridge_alloc() API")
>>>> Signed-off-by: Liu Ying <victor.liu@nxp.com>
>>>> ---
>>>>  drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>>>> index ed35e567d117..86cf898a09bb 100644
>>>> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>>>> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>>>> @@ -1474,7 +1474,7 @@ analogix_dp_probe(struct device *dev, struct analogix_dp_plat_data *plat_data)
>>>>  
>>>>  	dp = devm_drm_bridge_alloc(dev, struct analogix_dp_device, bridge,
>>>>  				   &analogix_dp_bridge_funcs);
>>>> -	if (!dp)
>>>> +	if (IS_ERR(dp))
>>>>  		return ERR_PTR(-ENOMEM);  
>>>
>>> Good catch, thanks!
>>>
>>> You fix is correct but now I realized one additional fix is needed in
>>> the following line:
>>>
>>> -		return ERR_PTR(-ENOMEM);
>>> +		return ERR_PTR(dp);  
>>
>> You mean ERR_CAST(dp)?
> 
> Ah, indeed!
> 
>>> Can you send a v2 with that fixed?  
>>
>> I find devm_drm_bridge_alloc() always returns ERR_PTR(-ENOMEM) in this
>> driver context, so it seems fine to keep the existing ERR_PTR(-ENOMEM).
>> If you prefer ERR_CAST(dp), I may send v2 to use ERR_CAST(dp).
> 
> The documentation says:
> 
>  * Returns:                  
>  * Pointer to new bridge, or ERR_PTR on failure.
> 
> So let's follow that, which is a (relatively) immutable contract, and
> not the implementation which might change over time.

Fair enough.  v2 is on the way.

> 
> This is also what all callers of devm_drm_bridge_alloc() do, unless I
> missed something.
> 
> Thanks,
> Luca
> 


-- 
Regards,
Liu Ying