linux-kernel - Re: [PATCH] n_tty: Don't lose characters when PARMRK is enabled

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Message-ID: <20120727140931.19ed2bf4@pyramind.ukuu.org.uk>
Date:	Fri, 27 Jul 2012 14:09:31 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Jaeden Amero <jaeden.amero@...com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] n_tty: Don't lose characters when PARMRK is enabled

On Thu, 26 Jul 2012 17:12:31 -0500
Jaeden Amero <jaeden.amero@...com> wrote:

> When PARMRK is set and large transfers of characters that will get
> marked are being received, n_tty could drop data silently (i.e.
> without reporting any error to the client). This is because
> characters have the potential to take up to three bytes in the line
> discipline (when they get marked with parity or framing errors), but
> the amount of free space reported to tty_buffer flush_to_ldisc (via
> tty->receive_room) is based on the pre-marked data size.
> 
> With this patch, the n_tty layer will no longer assume that each byte
> will only take up one byte in the line discipline. Instead, it will
> make an overly conservative estimate that each byte will take up
> three bytes in the line discipline when PARMRK is set.
> 
> Signed-off-by: Jaeden Amero <jaeden.amero@...com>

What a fun corner case. Patch looks good to me.

Acked-by: Alan Cox <alan@...ux.intel.com>
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