From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jaya Kumar" Subject: Re: [RFC 2.6.27 1/1] gpiolib: add support for batch set of pins Date: Sun, 30 Nov 2008 07:33:50 +0800 Message-ID: <45a44e480811291533ve0218dcvf07666064cb94d47@mail.gmail.com> References: <12276535632759-git-send-email-jayakumar.lkml@gmail.com> <45a44e480811252151q54580e07xfa73d69596fbfaac@mail.gmail.com> <20081127200102.GB20443@uranus.ravnborg.org> <200811291448.52483.david-b@pacbell.net> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200811291448.52483.david-b@pacbell.net> Content-Disposition: inline Sender: linux-embedded-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: David Brownell Cc: Sam Ravnborg , Eric Miao , 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 Jean emailed me saying he didn't want to be CCed. On Sun, Nov 30, 2008 at 6:48 AM, David Brownell wrote: > On Thursday 27 November 2008, Sam Ravnborg wrote: >> > > 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 > > All of those can also be handled with traditional parallel data > busses too, of course. Are you saying you've seen these used > with Linux systems? Enough to justify generic support? Assuming I've understood you correctly about generic support, yes. I used the 3 above with Linux arm systems that were interfaced to them via gpio. The matrix displays had just 128x64 so the 8x gpio_set_value penalty wasn't a biggie. The E-Ink displays range from 800x600 to 1200x826 so the 16x gpio_set_value became a bottleneck. In terms of generic support, the Broadsheet display controller is also used on i.MX31 and SC2410/2440 boards so those platform drivers (assuming those good folks submit them, (i've only written and submitted am300epd.c)) should also benefit. Thanks, jaya