linux-kernel - Re: [PATCH] OMAP: DSS: DPI: disable vt-switch on suspend/resume.

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Message-ID: <20150302210349.GE13270@amd>
Date:	Mon, 2 Mar 2015 22:03:49 +0100
From:	Pavel Machek <pavel@....cz>
To:	NeilBrown <neilb@...e.de>
Cc:	Tomi Valkeinen <tomi.valkeinen@...com>, linux-omap@...r.kernel.org,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	GTA04 owners <gta04-owner@...delico.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH] OMAP: DSS: DPI: disable vt-switch on suspend/resume.

Hi!

> > Looking at the drivers/tty/vt/vt_ioctl.c, it sounds to me that we should
> > always do pm_set_vt_switch(0), as omapdss restores everything just fine
> > on resume. Although it makes me wonder how it works if there are two
> > display controllers, one needing the switch and the other not...
> 
> I wondered that too.  It would seem to make more sense for
> pm_set_vt_switch(0) to be the default, that drivers which need the textmode
> switch should call (1).  But I suspect there are "historical reasons" for the
> current situation.

Well... historically, we did not have drivers for graphics cards --
kernel did not know how to handle it, only X knew. For cards that do
not have kernel driver, only X one, we need to switch vts.

For cards that have proper driver, we should be able to survive
without VT switch.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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