linux-kernel - Re: [RFC 2.6.27 1/1] gpiolib: add support for batch set of pins

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20081127200102.GB20443@uranus.ravnborg.org>
Date:	Thu, 27 Nov 2008 21:01:02 +0100
From:	Sam Ravnborg <sam@...nborg.org>
To:	Jaya Kumar <jayakumar.lkml@...il.com>
Cc:	David Brownell <david-b@...bell.net>,
	Eric Miao <eric.y.miao@...il.com>,
	Jean Delvare <khali@...ux-fr.org>,
	Eric Miao <eric.miao@...vell.com>,
	Haavard Skinnemoen <hskinnemoen@...el.com>,
	Philipp Zabel <philipp.zabel@...il.com>,
	Russell King <rmk@....linux.org.uk>,
	Ben Gardner <bgardner@...tec.com>, Greg KH <greg@...ah.com>,
	linux-arm-kernel@...ts.arm.linux.org.uk,
	linux-fbdev-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, linux-embedded@...r.kernel.org
Subject: Re: [RFC 2.6.27 1/1] gpiolib: add support for batch set of pins

On Wed, Nov 26, 2008 at 12:51:27AM -0500, Jaya Kumar wrote:
> On Tue, Nov 25, 2008 at 11:15 PM, David Brownell <david-b@...bell.net> wrote:
> > On Tuesday 25 November 2008, Eric Miao wrote:
> >> Using a bit mask will be more generic if the GPIOs are not contiguous.
> >> Yet I still doubt this will be generic enough to be added to gpiolib.
> >
> > My expectation for this kind of mechanism was that systems who need
> > to craft another parallel bus out of GPIO pins would be doing this
> > with some system-specific utility functions.
> >
> > So my "is it generic enough" question is more at the level of "Are
> > there enough Linux systems that need this sort of thing to justify
> > generic support?".  I happen not to have come across the need for
> > such ganged access from Linux (yet).  Whereas I've yet to use non-x86
> > Linux systems that don't need to manipulate individual GPIO pins...
> 
> I have come across the following scenarios where a bus set of gpio is useful:
> - Broadsheet E-Ink controller (uses 16-bit data bus over GPIO)
> framebuffer device (this patch is for this)
> - Apollo/Hecuba E-Ink controller (uses 8-bit data bus over GPIO)
> framebuffer device
> - 8-bit parallel IO matrix LCD controllers, such as the Samsung KS108,
> also Hitachi, etc

We have such a system at work. And we need fast acces to the gpio pins
when updating the LCD.
I have not written/looked to deep at the code I just recall it was
a bit messy and not something I would be proud of submitting to any ML.

	Sam
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/