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

[Liu Ying <victor.liu@nxp.com>]

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