linux-kernel - Re: tty/serial: Need clarification on Support for 4+M Baudrate

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Message-ID: <20120112114913.21809bed@pyramind.ukuu.org.uk>
Date:	Thu, 12 Jan 2012 11:49:13 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Rajanikanth H V <rajanikanth.hv@...ricsson.com>
Cc:	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"gregkh@...e.de" <gregkh@...e.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: tty/serial: Need clarification on Support for 4+M Baudrate

On Thu, 12 Jan 2012 10:49:38 +0100
Rajanikanth H V <rajanikanth.hv@...ricsson.com> wrote:

> Alan,
> 
> Thanks for your response, suggested modification helped to get 4.8M baud
> but not 4.05M as this is being approximated to 4.0M baud which happens in
> tty_termios_encode_baud_rate(...).

Only if you don't have the BOTHER flag set and only for returned data to
user space.

When you do a TCSETS2 ioctl and have BOTHER set as the rate as well as a
c_ispeed/c_ospeed the exactly value is given to the driver.

Alan
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