linux-kernel - Re: USB mass storage and ARM cache coherency

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Date:	Tue, 2 Feb 2010 13:07:56 +0100
From:	Oliver Neukum <oliver@...kum.org>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Matthew Dharm <mdharm-kernel@...-eyed-alien.net>,
	Sergei Shtylyov <sshtylyov@...mvista.com>,
	Ming Lei <tom.leiming@...il.com>, linux-usb@...r.kernel.org,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	Sebastian Siewior <bigeasy@...utronix.de>,
	Greg KH <greg@...ah.com>
Subject: Re: USB mass storage and ARM cache coherency

Am Dienstag, 2. Februar 2010 13:01:12 schrieb Catalin Marinas:
> On Tue, 2010-02-02 at 11:48 +0000, Oliver Neukum wrote:
> > Am Montag, 1. Februar 2010 18:29:14 schrieb Catalin Marinas:
> > > +       if (usb_pipein(urb->pipe) && usb_pipetype(urb->pipe) == PIPE_BULK) {
> > > +               void *ptr;
> > > +               for (ptr = urb->transfer_buffer;
> > > +                    ptr < urb->transfer_buffer + urb->transfer_buffer_length;
> > > +                    ptr += PAGE_SIZE)
> > > +                       flush_dcache_page(virt_to_page(ptr));
> > 
> > Is it correct to limit this to BULK pipes?
> 
> I'm not entirely sure. The flush_dcache_page() should only be called for
> pages that may be mapped into user space (page cache pages). We don't
> need this for control buffers. It was my impression that what's coming
> from the mass storage layer intended for page cache pages has the
> PIPE_BULK type (I may be wrong though).

For storage that is correct. But what about other sources of pages,
for example iSCSI?

	Regards
		Oliver
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