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

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Date:   Wed, 27 Apr 2022 12:03:21 -0700
From:   Tom Rix <trix@...hat.com>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>, mchehab@...nel.org,
        cai.huoqing@...ux.dev, paskripkin@...il.com, 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 4/26/22 10:38 PM, Hans Verkuil wrote:
> Hi Tom,
>
> On 12/03/2022 18:30, 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.
> I read the replies to this patch, but I am not certain if you still want
> this patch to be merged, or will make a v2. I have no problem applying this
> patch as-is, but I just want to have confirmation that there won't be a v2.

Merged as-is is fine.

Thanks

Tom


>
> Regards,
>
> 	Hans
>
>> 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)
>>   {
>>   	struct usb_device *udev = dev->udev;
>> -	unsigned char *buf;
>>   	int ret;
>>   
>> -	buf = kmalloc(sizeof(u8), GFP_KERNEL);
>> -	if (!buf)
>> -		return -ENOMEM;
>> -
>>   	ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
>>   			0x00,
>>   			USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
>>   			0x00,
>>   			index,
>> -			buf,
>> +			&dev->read_reg_scratch,
>>   			sizeof(u8),
>>   			500);
>>   	if (ret >= 0)
>> -		*value = *buf;
>> -
>> -	kfree(buf);
>> +		*value = dev->read_reg_scratch;
>>   
>>   	if (ret < 0)
>>   		return ret;
>> diff --git a/drivers/media/usb/stkwebcam/stk-webcam.h b/drivers/media/usb/stkwebcam/stk-webcam.h
>> index 14519e5308b18..136decffe9ced 100644
>> --- a/drivers/media/usb/stkwebcam/stk-webcam.h
>> +++ b/drivers/media/usb/stkwebcam/stk-webcam.h
>> @@ -105,6 +105,8 @@ struct stk_camera {
>>   	struct list_head sio_avail;
>>   	struct list_head sio_full;
>>   	unsigned sequence;
>> +
>> +	u8 read_reg_scratch;
>>   };
>>   
>>   #define vdev_to_camera(d) container_of(d, struct stk_camera, vdev)