linux-kernel - RE: About TRB_TO_EP

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Message-ID: <0C18FE92A7765D4EB9EE5D38D86A563A01966F92@SHSMSX103.ccr.corp.intel.com>
Date:	Tue, 6 Aug 2013 08:59:32 +0000
From:	"Du, ChangbinX" <changbinx.du@...el.com>
To:	"'gregkh@...uxfoundation.org'" <gregkh@...uxfoundation.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"balbi@...com" <balbi@...com>,
	"sarah.a.sharp@...uxfoundation.org" 
	<sarah.a.sharp@...uxfoundation.org>, "Wu, Hao" <hao.wu@...el.com>,
	"Tang, Jianqiang" <jianqiang.tang@...el.com>,
	"Zhuang, Jin Can" <jin.can.zhuang@...el.com>,
	"Huang, Xiaochao" <xiaochao.huang@...el.com>
Subject: RE: About TRB_TO_EP_INDEX() macro using

> On Mon, Aug 05, 2013 at 08:07:25AM +0000, Du, ChangbinX wrote:
> > Recently when I check xHCI code, find that some functions try to get EP index
> > from a Command Completion Event TRB via TRB_TO_EP_INDEX() macro.
> >
> > This is totally wrong. The macro definition is:
> >
> > 	#define TRB_TO_EP_INDEX(p)		((((p) & (0x1f << 16)) >> 16) - 1)
> >
> > TRB_TO_EP_INDEX only applies to Transfer Event TRB. But for Command
> > Completion Event TRB, there is no Endpoint ID field. So, we cannot directly
> > get EP index from these TRBs, but we can find it by the TRB Pointer.
> >
> > Here list two functions for you to check:
> > 	handle_stopped_endpoint()
> > 	handle_reset_ep_completion()
> 
> Care to send a patch showing how you would change this if it is
> incorrect?
> 
> thanks,
> 
> greg k-h
> --

Hello, Greg k-h. I am not very sure about this issue. If this is true, kernel will panic when 
invoking above functions. I want someone help to confirm if I miss something. If it's really 
a bug, I will work out a patch to fix it.
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