linux-kernel - Re: [PATCH 1/2] Export usb_serial_generic_write

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Date:	Sun, 24 Oct 2010 20:10:57 +0200
From:	Alon Ziv <alon@...aviz.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Greg KH <gregkh@...e.de>, Alon Ziv <alon+git@...aviz.org>,
	linux-usb@...r.kernel.org, Johan Hovold <jhovold@...il.com>,
	Stefani Seibold <stefani@...bold.net>,
	Jason Wessel <jason.wessel@...driver.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] Export usb_serial_generic_write_room for use in other
 modules

On 10/24/2010 10:37 AM, Alan Cox wrote:

>> The generic code does not invoke the write_room callback before invoking
>> break_ctl, so there is no way to use this function in usb_serial.
>>     
> Why would it ?
>
>   
Oops, typo...  Last sentence was supposed to end with "in usb_debug".
usb_debug invokes usb_serial_generic_write from break_ctl and ignores
the result; therefore, if there is no room in the generic write FIFO,
the write will fail.  However--usb_debug _only_ uses
usb_serial_generic_write for break_ctl; so if there is no room, it is
because of a previous (uncompleted) break_ctl, and according to standard
UART semantics there is no difference between one break and two...

-a
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