linux-kernel - Re: [PATCH] media: rockchip: rkisp1: remove some dead code

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Message-ID: <cedd1dd1-36c5-ff63-4092-e5f6b40e6286@collabora.com>
Date:   Tue, 1 Dec 2020 11:38:33 -0300
From:   Helen Koike <helen.koike@...labora.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Dafna Hirschfeld <dafna.hirschfeld@...labora.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>, linux-media@...r.kernel.org,
        linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] media: rockchip: rkisp1: remove some dead code

Hi Dan,

On 12/1/20 11:27 AM, Dan Carpenter wrote:
> On Mon, Nov 30, 2020 at 11:20:05AM -0300, Helen Koike wrote:
>> Hi Dan,
>>
>> Thank you for your patch.
>>
>> On 11/30/20 9:53 AM, Dan Carpenter wrote:
>>> The debugfs_create_dir() function never returns NULLs.  It's not supposed
>>> to checked for errors in the normal case and there is no need to check
>>> in this function so let's just delete this dead code.
>>>
>>> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
>>> ---
>>>  drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c | 4 ----
>>>  1 file changed, 4 deletions(-)
>>>
>>> diff --git a/drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c b/drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c
>>> index 9af137e4967f..68da1eed753d 100644
>>> --- a/drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c
>>> +++ b/drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c
>>> @@ -430,10 +430,6 @@ static void rkisp1_debug_init(struct rkisp1_device *rkisp1)
>>>  	struct rkisp1_debug *debug = &rkisp1->debug;
>>>  
>>>  	debug->debugfs_dir = debugfs_create_dir(RKISP1_DRIVER_NAME, NULL);
>>> -	if (!debug->debugfs_dir) {
>>> -		dev_dbg(rkisp1->dev, "failed to create debugfs directory\n");
>>> -		return;
>>> -	}
>>
>> I was taking a look at the debugfs_create_dir() code, and I saw it can
>> return ERR_PTR(), so ideally we should check for errors with IS_ERR() / PTR_ERR().
> 
> Debugfs functions aren't meant to be error checked in the normal case.
> There are some drivers which dereference the dentry pointer so those
> need to check it but that's not very common and isn't the case here.

right, I just saw the functions in inode.c already checks the parent with
IS_ERR(). the debugfs_create_*() function calls start_creating() which
already checks the parent.

ok, fair enough, I'll ack v2.

Regards,
Helen

> 
> I'm really sure this must be documented somewhere but I can't find it
> at all.  :P  But look at commit 057e212eae72 ("media: usb: uvc: no need
> to check return value of debugfs_create functions") for example.
> 
> regards,
> dan carpenter
>