linux-kernel - Re: [PATCH] media: st-mipid02: add a check for devm_gpiod_get

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Date:   Thu, 17 Oct 2019 12:24:04 +0000
From:   Mickael GUENE <mickael.guene@...com>
To:     Chuhong Yuan <hslester96@...il.com>
CC:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: st-mipid02: add a check for
 devm_gpiod_get_optional

Hello Chuhong,

 Sorry I missed 'if (PTR_ERR(desc) == -ENOENT)' check ....
 Can you in this case add an error message ?

Regards
Mickael
 
On 10/17/19 09:48, Chuhong Yuan wrote:
> On Thu, Oct 17, 2019 at 1:43 PM Mickael GUENE <mickael.guene@...com> wrote:
>>
>> Hello Chuhong,
>>
>>  Is this check necessary ?
>> since looking into code it seems to me devm_gpiod_get_optional() can only
>> return NULL in case of error due to following check in devm_gpiod_get_index_optional()
>>         if (IS_ERR(desc)) {
>>                 if (PTR_ERR(desc) == -ENOENT)
>>                         return NULL;
>>         }
>>  And in that case reset_gpio is not used
>>
> 
> The problem may not be a null return value, but a returned error,
> which is a minus value,
> like -EPROBE_DEFER or -EINVAL returned by gpiod_find in gpiod_get_index.
> In these cases, devm_gpiod_get_index_optional will not return null but
> return the error.
> Therefore, this check is necessary.
> 
>> Regards
>> Mickael
>>
>> On 10/16/19 12:56, Chuhong Yuan wrote:
>>> mipid02_probe misses a check for devm_gpiod_get_optional and may miss
>>> the failure.
>>> Add a check to fix the problem.
>>>
>>> Signed-off-by: Chuhong Yuan <hslester96@...il.com>
>>> ---
>>>  drivers/media/i2c/st-mipid02.c | 3 +++
>>>  1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/media/i2c/st-mipid02.c b/drivers/media/i2c/st-mipid02.c
>>> index 81285b8d5cfb..d38e888b0a43 100644
>>> --- a/drivers/media/i2c/st-mipid02.c
>>> +++ b/drivers/media/i2c/st-mipid02.c
>>> @@ -971,6 +971,9 @@ static int mipid02_probe(struct i2c_client *client)
>>>       bridge->reset_gpio = devm_gpiod_get_optional(dev, "reset",
>>>                                                    GPIOD_OUT_HIGH);
>>>
>>> +     if (IS_ERR(bridge->reset_gpio))
>>> +             return PTR_ERR(bridge->reset_gpio);
>>> +
>>>       ret = mipid02_get_regulators(bridge);
>>>       if (ret) {
>>>               dev_err(dev, "failed to get regulators %d", ret);
>>>