Re: [v2 05/11] rsi: Remove unnecessary buffer allocation

[Kalle Valo <kvalo@codeaurora.org>]

Amitkumar Karwar <amitkarwar@gmail.com> writes:

> From: Prameela Rani Garnepudi <prameela.j04cs@gmail.com>
>
> In functions usb read register and usb write register, dynamic allocation
> of 4 bytes is used. This is removed as it is unncessary for local variable
> and for such small data.
>
> Signed-off-by: Prameela Rani Garnepudi <prameela.j04cs@gmail.com>
> Signed-off-by: Amitkumar Karwar <amit.karwar@redpinesignals.com>
> ---
>  drivers/net/wireless/rsi/rsi_91x_usb.c | 18 ++++--------------
>  1 file changed, 4 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/net/wireless/rsi/rsi_91x_usb.c b/drivers/net/wireless/rsi/rsi_91x_usb.c
> index 73b01a8..8eb7407 100644
> --- a/drivers/net/wireless/rsi/rsi_91x_usb.c
> +++ b/drivers/net/wireless/rsi/rsi_91x_usb.c
> @@ -157,12 +157,8 @@ static int rsi_usb_reg_read(struct usb_device *usbdev,
>  			    u16 *value,
>  			    u16 len)
>  {
> -	u8 *buf;
> -	int status = -ENOMEM;
> -
> -	buf  = kmalloc(0x04, GFP_KERNEL);
> -	if (!buf)
> -		return status;
> +	u8 buf[4];
> +	int status;
>  
>  	status = usb_control_msg(usbdev,
>  				 usb_rcvctrlpipe(usbdev, 0),

Recently I got a patch to orinoco_usb which did exactly the opposite
(unless I'm missing something):

https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/wireless-drivers-next.git/commit/?id=2f6ae79cb04bb7f9b4be3f1c32b6fda35bf976bc

The documentation for usb_control_msg() does not mention anything if
it's possible to use stack memory, but AFAIU it's not possible to use
stack memory with DMA. Can anyone clarify?

-- 
Kalle Valo