Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755424AbYK2XeG (ORCPT ); Sat, 29 Nov 2008 18:34:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752995AbYK2Xdx (ORCPT ); Sat, 29 Nov 2008 18:33:53 -0500 Received: from nf-out-0910.google.com ([64.233.182.189]:12671 "EHLO nf-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752915AbYK2Xdw (ORCPT ); Sat, 29 Nov 2008 18:33:52 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=jRi7Su8J6nJ31SYiQoPL8PLuIBqPJ7sL8yJBJNNq01bKYfQlMcb7MoIB1vzhwoF2ch 2ceAwX0It03E8okAW0BxAPfLTtojJ/o/XqePo7pMwLakZ188rVHBCh/YGqH2rEX5yJnn ySA6VzlGfx25Ra5rbO7zDIiRFSkEEPRBKeLn8= Message-ID: <45a44e480811291533ve0218dcvf07666064cb94d47@mail.gmail.com> Date: Sun, 30 Nov 2008 07:33:50 +0800 From: "Jaya Kumar" To: "David Brownell" Subject: Re: [RFC 2.6.27 1/1] gpiolib: add support for batch set of pins 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 In-Reply-To: <200811291448.52483.david-b@pacbell.net> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <12276535632759-git-send-email-jayakumar.lkml@gmail.com> <45a44e480811252151q54580e07xfa73d69596fbfaac@mail.gmail.com> <20081127200102.GB20443@uranus.ravnborg.org> <200811291448.52483.david-b@pacbell.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1980 Lines: 39 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 -- 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/