Re: [PATCH 17/24] usb: host: xhci: Remove unused variable 'len'

Lee Jones
2021-05-27T11:06:27Z

On Thu, 27 May 2021, Mathias Nyman wrote:

> On 27.5.2021 11.16, Lee Jones wrote:
> > On Thu, 27 May 2021, Greg Kroah-Hartman wrote:
> >
> >> On Wed, May 26, 2021 at 02:00:30PM +0100, Lee Jones wrote:
> >>> Fixes the following W=1 kernel build warning(s):
> >>>
> >>> drivers/usb/host/xhci.c: In function ‘xhci_unmap_temp_buf’:
> >>> drivers/usb/host/xhci.c:1349:15: warning: variable ‘len’ set but not used [-Wunused-but-set-variable]
> >>>
> >>> Cc: Mathias Nyman <mathias.nyman@intel.com>
> >>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >>> Cc: linux-usb@vger.kernel.org
> >>> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> >>> ---
> >>> drivers/usb/host/xhci.c | 9 ++++-----
> >>> 1 file changed, 4 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> >>> index 27283654ca080..ac2a7d4288883 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;
> >>>
> >>> @@ -1362,10 +1361,10 @@ 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,
> >>> - urb->transfer_buffer,
> >>> - buf_len,
> >>> - 0);
> >>> + sg_pcopy_from_buffer(urb->sg, urb->num_sgs,
> >>> + urb->transfer_buffer,
> >>> + buf_len,
> >>> + 0);
> >>
> >> Sorry, but no, I keep rejecting this over and over, it needs to handle
> >> the error handling properly and not paper over it like this :(
> >
> > Will fix.
> >
> >> All the bots keep tripping up on it, you are not alone.
> >
>
> This is getting a lot of attention. Something like this should fix it:
>
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 27283654ca08..306ab81421fd 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -1361,12 +1361,16 @@ static void xhci_unmap_temp_buf(struct usb_hcd *hcd, struct urb *urb)
> urb->transfer_buffer_length,
> dir);
>
> - if (usb_urb_dir_in(urb))
> + if (usb_urb_dir_in(urb)) {
> len = sg_pcopy_from_buffer(urb->sg, urb->num_sgs,
> urb->transfer_buffer,
> buf_len,
> 0);
> -
> + if (len != buf_len) {
> + xhci_dbg(xhci, "Copy from tmp buf to urb sg list failed\n");
> + urb->actual_length = len;
> + }
> + }
> urb->transfer_flags &= ~URB_DMA_MAP_SINGLE;
> kfree(urb->transfer_buffer);
> urb->transfer_buffer = NULL;
>
> urb->actual_length is now properly set.
> The debug level message will help me find the cause if we ever need
> to debug oddly behaving devices.
>
> Note this is a very rarly taken codepath for quirky xHC harware that
> can't handle a specific sequence of buffer lengths queued.
>
> I can write a proper commit message and push this forward

Okay by me.

--
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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