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

[Gonglei]

On 2015/4/29 14:48, Michael Tokarev wrote:
> 28.04.2015 12:11, address@hidden wrote:
>> From: Gonglei <address@hidden>
>>
>> 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 <address@hidden>
>> Signed-off-by: Gonglei <address@hidden>
>> ---
>>  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 can't agree with you more. :)

Regards,
-Gonglei

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