linux-kernel - Re: [PATCH 2/2] fbcon: expose cursor blink interval via sysfs

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Message-ID: <20150226220243.GC9935@amd>
Date:	Thu, 26 Feb 2015 23:02:43 +0100
From:	Pavel Machek <pavel@....cz>
To:	Scot Doyle <lkml14@...tdoyle.com>
Cc:	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	linux-fbdev@...r.kernel.org, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] fbcon: expose cursor blink interval via sysfs

On Wed 2015-02-25 23:32:00, Scot Doyle wrote:
> On Wed, 25 Feb 2015, Pavel Machek wrote:
> > On Mon 2015-01-26 20:41:53, Scot Doyle wrote:
> > > The fbcon cursor, when set to blink, is hardcoded to toggle display state
> > > five times per second. Expose this setting via
> > > /sys/class/graphics/fbcon/cursor_blink_ms
> > > 
> > > Values written to the interface set the approximate time interval in
> > > milliseconds between cursor toggles, from 1 to 32767. Since the interval
> > > is stored internally as a number of jiffies, the millisecond value read
> > > from the interface may not exactly match the entered value.
> > > 
> > > An outstanding blink timer is reset after a new value is entered.
> > > 
> > > If the cursor blink is disabled, either via the 'cursor_blink' boolean
> > > setting or some other mechanism, the 'cursor_blink_ms' setting may still
> > > be modified. The new value will be used if the blink is reactivated.
> > > 
> > > Signed-off-by: Scot Doyle <lkml14@...tdoyle.com>
> > 
> > Normally, this would be set by ansi escape sequences, no? We can hide
> > cursor using them, set its appearance.. makes sense to change timing
> > value there, too....
> > 									Pavel
> 
> Hi Pavel, what about something like this? For example,
> "echo -e '\033[16;500]' would set the blink interval to 500 milliseconds.
> 
> The duration is stored twice to avoid locking the console in
> cursor_timer_handler().

Yes, I'd say this matches the existing code better.

Acked-by: Pavel Machek <pavel@....cz>

> +		case 16: /* set cursor blink duration in msec */
> +			if (vc->vc_npar >= 1 && vc->vc_par[1] > 0 &&
> +					vc->vc_par[1] <= USHRT_MAX)
> +				vc->vc_cur_blink_ms = vc->vc_par[1];
> +			else

Actually, vc_cur_blink_ms less then about 50 probably does not make
sense (and may overload the system). Should that be checked?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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