linux-kernel - Re: usb: dwc3: ep0: return early on NULL requests

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Date:	Mon, 10 Nov 2014 14:37:39 -0600
From:	Felipe Balbi <balbi@...com>
To:	Dave Jones <davej@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	<balbi@...com>
Subject: Re: usb: dwc3: ep0: return early on NULL requests

On Mon, Nov 10, 2014 at 03:32:29PM -0500, Dave Jones wrote:
> On Sat, Nov 01, 2014 at 10:20:47PM +0000, Linux Kernel wrote:
>  > Gitweb:     http://git.kernel.org/linus/;a=commit;h=6856d30c6c0038dc0648009853533af3af6c5ba8
>  > Commit:     6856d30c6c0038dc0648009853533af3af6c5ba8
>  > Parent:     7d643664ea559b36188cae264047ce3c9bfec3a2
>  > Refname:    refs/heads/master
>  > Author:     Felipe Balbi <balbi@...com>
>  > AuthorDate: Tue Sep 30 11:43:20 2014 -0500
>  > Committer:  Felipe Balbi <balbi@...com>
>  > CommitDate: Mon Oct 20 15:58:49 2014 -0500
>  > 
>  >     usb: dwc3: ep0: return early on NULL requests
>  >     
>  >     if our list of requests is empty, return early.
> 
> ....
> 
>  > diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
>  > index ae6b575..a47cc1e 100644
>  > --- a/drivers/usb/dwc3/ep0.c
>  > +++ b/drivers/usb/dwc3/ep0.c
>  > @@ -789,9 +789,6 @@ static void dwc3_ep0_complete_data(struct dwc3 *dwc,
>  >  
>  >  	dwc->ep0_next_event = DWC3_EP0_NRDY_STATUS;
>  >  
>  > -	r = next_request(&ep0->request_list);
>  > -	ur = &r->request;
>  > -
>  >  	trb = dwc->ep0_trb;
> 
>  
> Since the deletion of this assignment to 'r', we're now doing
> a comparison on it, resulting in dead code that will never be
> reached..

very true, here's a patch to fix it up again :-) i'll send it properly
in a bit.

diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
index 711b230..df38e7e 100644
--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -791,6 +791,10 @@ static void dwc3_ep0_complete_data(struct dwc3 *dwc,
 
 	trb = dwc->ep0_trb;
 
+	r = next_request(&ep0->request_list);
+	if (!r)
+		return;
+
 	status = DWC3_TRB_SIZE_TRBSTS(trb->size);
 	if (status == DWC3_TRBSTS_SETUP_PENDING) {
 		dwc3_trace(trace_dwc3_ep0, "Setup Pending received");
@@ -801,10 +805,6 @@ static void dwc3_ep0_complete_data(struct dwc3 *dwc,
 		return;
 	}
 
-	r = next_request(&ep0->request_list);
-	if (!r)
-		return;
-
 	ur = &r->request;
 
 	length = trb->size & DWC3_TRB_SIZE_MASK;

-- 
balbi

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