From: Oliver Neukum <oliver@neukum.org>
Organization: NOvell
To: "Francis Moreau" <francis.moro@gmail.com>
Subject: Re: usb_get_status(): what a weird implementation !
Date: Mon, 30 Jun 2008 16:11:41 +0200
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Cc: "David Brownell" <david-b@pacbell.net>, linux-usb@vger.kernel.org,
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Am Montag 30 Juni 2008 16:03:52 schrieb Francis Moreau:
> On Mon, Jun 30, 2008 at 3:51 PM, Oliver Neukum <oliver@neukum.org> wrote:
> >
> > If your buffer is smaller than CACHE_LINE_SIZE it should work.
> > However, this needs input from people who understand DMA in and out.
> 
> yeah, that's the reason why it's a hack.
> 
> Maybe adding a new helper in  the dma API would be better...
> 
> > But how large is 2 * CACHE_LINE_SIZE compared to the kernel stack?
> 
> CACHE_LINE_SIZE = 32 bytes is common for embedded systems I guess.
> For big system, I dunno.
> 
> Kernel stack size is usually  4KiB.
> 

Well, we have:
asm-mips/mach-ip32/kmalloc.h:#define ARCH_KMALLOC_MINALIGN      128
That's 256 bytes, that is 1/16 of the stack.

	Regards
		Oliver

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