linux-kernel - Re: About TRB_TO_EP

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Message-ID: <20130805083445.GA15885@kroah.com>
Date:	Mon, 5 Aug 2013 16:34:45 +0800
From:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To:	"Du, ChangbinX" <changbinx.du@...el.com>
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
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