linux-kernel - Re: [PATCH 5/5] usb_debug: EXPERIMENTAL

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Date:	Wed, 6 May 2009 08:45:06 -0700
From:	Greg KH <greg@...ah.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Jason Wessel <jason.wessel@...driver.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] usb_debug: EXPERIMENTAL - poll hcd device to force
	writes

On Wed, May 06, 2009 at 04:41:41PM +0100, Alan Cox wrote:
> In other words never lie in the write_room method. Try to send data as
> early as possible, but don't queue data inefficiently when the port has
> plenty left to send.
> 
> The rules for write_room are simple
> 
> 	If you say you have space for X bytes you can't say you have room
> 	for less bytes unless those bytes have actually been written - no
> 	window shrinking so to speak.
> 
> If your write_room method works properly, and you fix the buffering logic
> then the rest will work. Probably we need usb/serial/buffer.c which has a
> generic implementation in then that can be used to replace the completely
> bogus hacks in most of the drivers.

I agree, this is the correct solution.

thanks,

greg k-h
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