linux-kernel - Re: [PATCH v2 1/3] net/usb/r815x: replace USB buffer from stack to DMA-able

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Message-Id: <20130727.202107.555068116238400560.davem@davemloft.net>
Date:	Sat, 27 Jul 2013 20:21:07 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	hayeswang@...ltek.com
Cc:	gregkh@...uxfoundation.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v2 1/3] net/usb/r815x: replace USB buffer from stack to
 DMA-able

From: Hayes Wang <hayeswang@...ltek.com>
Date: Thu, 25 Jul 2013 15:59:02 +0800

> Some USB buffers use stack which may not be DMA-able.
> Use the buffers from kmalloc to replace those one.
> 
> Signed-off-by: Hayes Wang <hayeswang@...ltek.com>

I don't think it's reasonable to kmalloc() a small integer every time
you want to use a USB message transfer to read or write chip
registers.

Instead, add a scratch buffer to struct r8152 which is allocated once
at driver attach time and which you can use for the transfers.

I think you only need an array of two u32's so something like:

	u32		transfer_buf[2];

ought to be sufficient.

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