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Message-ID: <20090506154506.GB4941@kroah.com>
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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