Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754274AbYK0T7u (ORCPT ); Thu, 27 Nov 2008 14:59:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752738AbYK0T7k (ORCPT ); Thu, 27 Nov 2008 14:59:40 -0500 Received: from pfepb.post.tele.dk ([195.41.46.236]:34755 "EHLO pfepb.post.tele.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752376AbYK0T7k (ORCPT ); Thu, 27 Nov 2008 14:59:40 -0500 Date: Thu, 27 Nov 2008 21:01:02 +0100 From: Sam Ravnborg To: Jaya Kumar Cc: David Brownell , Eric Miao , Jean Delvare , Eric Miao , Haavard Skinnemoen , Philipp Zabel , Russell King , Ben Gardner , Greg KH , linux-arm-kernel@lists.arm.linux.org.uk, linux-fbdev-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-embedded@vger.kernel.org Subject: Re: [RFC 2.6.27 1/1] gpiolib: add support for batch set of pins Message-ID: <20081127200102.GB20443@uranus.ravnborg.org> References: <12276535632759-git-send-email-jayakumar.lkml@gmail.com> <200811252015.57870.david-b@pacbell.net> <45a44e480811252151q54580e07xfa73d69596fbfaac@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45a44e480811252151q54580e07xfa73d69596fbfaac@mail.gmail.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1759 Lines: 35 On Wed, Nov 26, 2008 at 12:51:27AM -0500, Jaya Kumar wrote: > On Tue, Nov 25, 2008 at 11:15 PM, David Brownell 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/