Re: [PATCH 1/1] usb: xhci: remove unused variable 'len' in xhci_unmap_temp_buf()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Wed, May 19, 2021 at 10:37:07PM +0800, Leizhen (ThunderTown) wrote:
> 
> 
> On 2021/5/19 21:40, Leizhen (ThunderTown) wrote:
> > 
> > 
> > On 2021/5/19 21:12, Greg Kroah-Hartman wrote:
> >> On Wed, May 19, 2021 at 08:33:04PM +0800, Zhen Lei wrote:
> >>> GCC reports the following warning with W=1:
> >>>
> >>> drivers/usb/host/xhci.c:1349:15: warning:
> >>>  variable 'len' set but not used [-Wunused-but-set-variable]
> >>>  1349 |  unsigned int len;
> >>>       |               ^~~
> >>>
> >>> This variable is not used, remove it to fix the warning.
> >>>
> >>> Reported-by: Hulk Robot <hulkci@huawei.com>
> >>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> >>> ---
> >>>  drivers/usb/host/xhci.c | 3 +--
> >>>  1 file changed, 1 insertion(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> >>> index 27283654ca08..a75ed4a00997 100644
> >>> --- a/drivers/usb/host/xhci.c
> >>> +++ b/drivers/usb/host/xhci.c
> >>> @@ -1346,7 +1346,6 @@ static bool xhci_urb_temp_buffer_required(struct usb_hcd *hcd,
> >>>  
> >>>  static void xhci_unmap_temp_buf(struct usb_hcd *hcd, struct urb *urb)
> >>>  {
> >>> -	unsigned int len;
> >>>  	unsigned int buf_len;
> >>>  	enum dma_data_direction dir;
> >>>  
> >>> @@ -1362,7 +1361,7 @@ static void xhci_unmap_temp_buf(struct usb_hcd *hcd, struct urb *urb)
> >>>  				 dir);
> >>>  
> >>>  	if (usb_urb_dir_in(urb))
> >>> -		len = sg_pcopy_from_buffer(urb->sg, urb->num_sgs,
> >>> +		(void)sg_pcopy_from_buffer(urb->sg, urb->num_sgs,
> >>>  					   urb->transfer_buffer,
> >>>  					   buf_len,
> >>>  					   0);
> >>> -- 
> >>> 2.25.1
> >>>
> >>>
> >>
> >> Wow, no.  I keep telling you that this is not ok.  Why keep sending
> >> this?
> > 
> > Sorry, I forgot to google it, someone already posted it.
> 
> Hi, Greg Kroah-Hartman:
>   I've read your two exchange emails from https://patchwork.kernel.org/project/linux-usb/patch/20210306120644.74406-1-zhangkun4jr@163.com/#24019765
>   How about just give a warning when the copy is not complete? This W=1 warning will probably be detected by someone else.

Handle the error properly.  Just spitting a message to a user where they
can't do anything about it does not seems like the correct solution to
me, would you want the kernel to do that?

thanks,

greg k-h