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SubjectRe: [PATCH] media: stkwebcam: move stk_camera_read_reg() scratch buffer to struct stk_camera
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Hi Trix,

On 3/12/22 20:30, trix@redhat.com wrote:
> From: Tom Rix <trix@redhat.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@redhat.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);


Wouldn't it be better to move to modern USB API like usb_control_msg_recv()?

This API does not require buffer to be allocated via kmalloc(), so you
will be able to use value directly.




With regards,
Pavel Skripkin

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