linux-kernel - Re: [PATCH 2/2] USB: ehci: tegra: Align DMA transfers to 32 bytes

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Message-ID: <20101218012937.GM25105@morell.nvidia.com>
Date:	Fri, 17 Dec 2010 17:29:38 -0800
From:	rmorell@...dia.com
To:	Greg KH <gregkh@...e.de>
Cc:	David Brownell <dbrownell@...rs.sourceforge.net>,
	Benoit Goby <benoit@...roid.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Ming Lei <tom.leiming@...il.com>,
	Jacob Pan <jacob.jun.pan@...el.com>,
	Olof Johansson <olof@...om.net>,
	Erik Gilling <konkers@...roid.com>,
	Colin Cross <ccross@...roid.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] USB: ehci: tegra: Align DMA transfers to 32 bytes

On Fri, Dec 17, 2010 at 04:37:47PM -0800, Greg KH wrote:
> On Fri, Dec 17, 2010 at 03:40:08PM -0800, rmorell@...dia.com wrote:
> > On Fri, Dec 17, 2010 at 03:09:40PM -0800, Greg KH wrote:
> > > On Fri, Dec 17, 2010 at 02:42:21PM -0800, rmorell@...dia.com wrote:
> > > > On Fri, Dec 17, 2010 at 02:35:02PM -0800, Greg KH wrote:
> > > > > On Fri, Dec 17, 2010 at 01:58:49PM -0800, Robert Morell wrote:
> > > > > > --- a/include/linux/usb.h
> > > > > > +++ b/include/linux/usb.h
> > > > > > @@ -975,6 +975,7 @@ extern int usb_disabled(void);
> > > > > >  #define URB_SETUP_MAP_SINGLE	0x00100000	/* Setup packet DMA mapped */
> > > > > >  #define URB_SETUP_MAP_LOCAL	0x00200000	/* HCD-local setup packet */
> > > > > >  #define URB_DMA_SG_COMBINED	0x00400000	/* S-G entries were combined */
> > > > > > +#define URB_DRIVER_PRIVATE	0x80000000	/* For driver-private use */
> > > > > 
> > > > > Um, what?  You are using this for a build check, which seems pointless
> > > > > as you already modified the code to not need this.
> > > > > 
> > > > > So it doesn't look like this is needed, right?
> > > > 
> > > > The intention was to reserve space in the URB flags for
> > > > implementation-specific use.
> > > 
> > > Yes, but _which_ driver are you talking about here?  You didn't say that
> > > this was a HCD-only flag, right?
> > 
> > Sorry, I may not have been clear.  I did mean HCD-only flag; its exact
> > meaning depends on the HCD in question.  In the case of tegra-ehci, it
> > means that a temporary buffer has been allocated that needs freeing
> > later.
> > 
> > Would it make more sense if I called it URB_HCD_PRIVATE_MASK?
> 
> How about naming it what it is being used for?

Sure, I can do that.  I was just trying to avoid polluting the general
USB namespace with HCD-specific constants, but I'll send out a revised
patchset with this change.

Thanks,
Robert
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