linux-kernel - Re: [Gta04-owner] [PATCH 3/3] tty/slaves: add a driver to power on/off UART attached devices.

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Date:	Wed, 25 Mar 2015 21:42:02 +0100
From:	Pavel Machek <pavel@....cz>
To:	"Dr. H. Nikolaus Schaller" <hns@...delico.com>
Cc:	NeilBrown <neilb@...e.de>,
	List for communicating with real GTA04 owners 
	<gta04-owner@...delico.com>, Mark Rutland <mark.rutland@....com>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Peter Hurley <peter@...leysoftware.com>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sebastian Reichel <sre@...nel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Jiri Slaby <jslaby@...e.cz>, devicetree@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [Gta04-owner] [PATCH 3/3] tty/slaves: add a driver to power
 on/off UART attached devices.

Hi!

> > In the case of our GPS, it receives control over the serial connection from
> > the UART,
> 
> Ahem - does it?
> 
> AFAIK the chip simply starts to emit NMEA records if powered on. There is no
> command going over the serial interface to address it or control it.

Well _most_ GPSes enable you to control them over the serial
line. (Things like sampling rate, AGPS data upload, ...)

> > I think the GPS is “primarily" a uart-attached device.
> 
> But not in the same way as an I2C device.
> 
> Especially the serial interface is not a bus and not used for signalling and
> power control. It is payload data (only).

Serial interface looks a lot like a (point-to-point) bus to
me. Similar to SATA, for example.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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