linux-kernel - Re: [RFT] rtl8187: use DMA-aware buffers with usb_control

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Message-ID: <20090509163523.GA1200@kroah.com>
Date:	Sat, 9 May 2009 09:35:23 -0700
From:	Greg KH <greg@...ah.com>
To:	"John W. Linville" <linville@...driver.com>
Cc:	Eric Valette <eric.valette@...e.fr>,
	Hin-Tak Leung <hintak.leung@...il.com>,
	linux-wireless@...r.kernel.org,
	Larry Finger <Larry.Finger@...inger.net>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [RFT] rtl8187: use DMA-aware buffers with usb_control_msg

On Sat, May 09, 2009 at 11:50:14AM -0400, John W. Linville wrote:
> > usb_control messages are slow and should not be on the "fast path" of
> > any data being sent through the device.  Any overhead of the
> > kmalloc/kfree is totally eaten up by the actual transmission turn around
> > time of the message itself, so you don't have to worry about the
> > performance impact.
> 
> Yeah, I don't like the original version either.  Even if the kmalloc's
> aren't a big performance hit, the failure path sucks.  I've included a
> new version below, but unfortunately I haven't had a chance to test it.
> Please give it a try if you get a chance?

Looks good to me, a bit cleaner even.

thanks,

greg k-h
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