From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sam Ravnborg Subject: Re: [RFC 2.6.27 1/1] gpiolib: add support for batch set of pins Date: Thu, 27 Nov 2008 21:01:02 +0100 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 Return-path: Content-Disposition: inline In-Reply-To: <45a44e480811252151q54580e07xfa73d69596fbfaac@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 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