linux-kernel - Re: [PATCH V6] serial/uart/8250: Add tunable RX interrupt trigger I/F of FIFO buffers

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Message-ID: <535573D5.9050805@wwwdotorg.org>
Date:	Mon, 21 Apr 2014 13:39:01 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Stephen Warren <swarren@...dia.com>,
	Alan <gnomes@...rguk.ukuu.org.uk>
CC:	Jingoo Han <jg1.han@...sung.com>, linux-kernel@...r.kernel.org,
	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>,
	linux-serial@...r.kernel.org, yrl.pp-manager.tt@...achi.com,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Aaron Sierra <asierra@...-inc.com>, Jiri Slaby <jslaby@...e.cz>
Subject: Re: [PATCH V6] serial/uart/8250: Add tunable RX interrupt trigger
 I/F of FIFO buffers

On 04/17/2014 12:06 AM, Yoshihiro YUNOMAE wrote:
> Add tunable RX interrupt trigger I/F of FIFO buffers.
> Serial devices are used as not only message communication devices but control
> or sending communication devices. For the latter uses, normally small data
> will be exchanged, so user applications want to receive data unit as soon as
> possible for real-time tendency. If we have a sensor which sends a 1 byte data
> each time and must control a device based on the sensor feedback, the RX
> interrupt should be triggered for each data.
> 
> According to HW specification of serial UART devices, RX interrupt trigger
> can be changed, but the trigger is hard-coded. For example, RX interrupt trigger
> in 16550A can be set to 1, 4, 8, or 14 bytes for HW, but current driver sets
> the trigger to only 8bytes.
> 
> This patch makes some devices change RX interrupt trigger from userland.

Reviewed-by: Stephen Warren <swarren@...dia.com>
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