Re: [Qemu-devel] [PATCH 2/3] xhci: remove unused code

[Michael Tokarev <mjt@tls.msk.ru>]

28.04.2015 12:11, arei.gonglei@huawei.com wrote:
> From: Gonglei <arei.gonglei@huawei.com>
> 
> Value from xfer->packet.ep is assigned to ep here, but that
> stored value is not used before it is overwritten. Remove it.
> 
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Signed-off-by: Gonglei <arei.gonglei@huawei.com>
> ---
>  hw/usb/hcd-xhci.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/hw/usb/hcd-xhci.c b/hw/usb/hcd-xhci.c
> index ba15ae0..99f11fc 100644
> --- a/hw/usb/hcd-xhci.c
> +++ b/hw/usb/hcd-xhci.c
> @@ -2204,7 +2204,6 @@ static void xhci_kick_ep(XHCIState *xhci, unsigned int slotid,
>          if (epid == 1) {
>              if (xhci_fire_ctl_transfer(xhci, xfer) >= 0) {
>                  epctx->next_xfer = (epctx->next_xfer + 1) % TD_QUEUE;
> -                ep = xfer->packet.ep;
>              } else {
>                  DPRINTF("xhci: error firing CTL transfer\n");
>              }

This one is somewhat fun.  ep variable is not used in whole this
function until the very end, with the code:


    ep = xhci_epid_to_usbep(xhci, slotid, epid);
    if (ep) {
        usb_device_flush_ep_queue(ep->dev, ep);
    }

There are only 2 assignments to it here, it is the NULL
initializer and this place which is being removed by this
patch (which is obviously unused).

So, I think if we were to drop this assignment, we should
remove the initializer too.  But before doing this, I think
we should try to remember _why_ this assignment is here in
the first place. The code looks like after the loop, this
ep variable was supposed to be used for something.  Or is
it just a leftover from 518ad5f2a075 (Cc'ing the author)?

I haven't looked at all this in more details without good
knowlege of the protocol and background.

Thanks,

/mjt