linux-kernel - Re: [PATCH] media: stkwebcam: move stk_camera_read_reg() scratch buffer to struct stk

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Date:   Sat, 12 Mar 2022 15:48:39 -0800
From:   Tom Rix <trix@...hat.com>
To:     Pavel Skripkin <paskripkin@...il.com>, mchehab@...nel.org,
        hverkuil-cisco@...all.nl, cai.huoqing@...ux.dev,
        xose.vazquez@...il.com
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: stkwebcam: move stk_camera_read_reg() scratch
 buffer to struct stk_camera


On 3/12/22 11:58 AM, Pavel Skripkin wrote:
> On 3/12/22 20:30, trix@...hat.com wrote:
>> From: Tom Rix <trix@...hat.com>
>>
>> In stk_camera_read_reg() a single byte buffer is alloc-ed and
>> freed on every function call.  Since the size is known,
>> move the buffer to the struct stk_camera where it will be alloc-ed
>> and freed once.
>>
>> Signed-off-by: Tom Rix <trix@...hat.com>
>> ---
>>   drivers/media/usb/stkwebcam/stk-webcam.c | 11 ++---------
>>   drivers/media/usb/stkwebcam/stk-webcam.h |  2 ++
>>   2 files changed, 4 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/media/usb/stkwebcam/stk-webcam.c 
>> b/drivers/media/usb/stkwebcam/stk-webcam.c
>> index 5b822214ccc5c..787edb3d47c23 100644
>> --- a/drivers/media/usb/stkwebcam/stk-webcam.c
>> +++ b/drivers/media/usb/stkwebcam/stk-webcam.c
>> @@ -150,25 +150,18 @@ int stk_camera_write_reg(struct stk_camera 
>> *dev, u16 index, u8 value)
>>   int stk_camera_read_reg(struct stk_camera *dev, u16 index, u8 *value)
>
> And just random note: there are 4 possible uninit value bugs.
>
> stk_start_stream() calls stk_camera_read_reg 4 times, but ignores 
> return values.
>
> stk_camera_read_reg() should have __must_check annotation and return 
> value should be checked on each call.
>
>
> If you have time you can take care of it :) Or I will fix it one day...

These do show up in my usual static analysis and it why I was looking at 
this file.

And was sidetracked by the short malloc.

Unfortunately I looked and there are many other similar instances 
treewide ~100

These aren't caught in checkpatch, so working on that..

Tom

>
>
>
>
>
> With regards,
> Pavel Skripkin
>