From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-gx0-f172.google.com (mail-gx0-f172.google.com [209.85.217.172]) by ozlabs.org (Postfix) with ESMTP id 80B3ADDFA3 for ; Wed, 13 May 2009 11:16:09 +1000 (EST) Received: by gxk20 with SMTP id 20so658475gxk.9 for ; Tue, 12 May 2009 18:16:07 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <4A0A109F.7070803@dlasys.net> References: <1242007203.7767.28.camel@concordia> <4A085612.9050602@dlasys.net> <4A089AC8.9080704@dlasys.net> <20090512011219.GB18223@yookeroo.seuss> <20090512232446.GB24338@yookeroo.seuss> <4A0A109F.7070803@dlasys.net> From: Grant Likely Date: Tue, 12 May 2009 19:15:47 -0600 Message-ID: Subject: Re: device trees. To: "David H. Lynch Jr." Content-Type: text/plain; charset=ISO-8859-1 Cc: linuxppc-dev@ozlabs.org, David Gibson List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Whenever I say firmware I mean executable code that executes when the processor comes out of reset. When I mean the FPGA bitstream, I say bitstream. :-) g. On Tue, May 12, 2009 at 6:13 PM, David H. Lynch Jr. wrot= e: > > > =A0 =A0Are we all using the same meaning of firmware ? > > =A0 =A0While firmware =3D=3D BIOS is the norm for PC's > =A0 =A0 atleast in the embedded FPGA space firmware could mean the FPGA > programing that creates the hardware. > =A0 =A0For an FPGA based system a dtb generated by the same software that > created the "firmware" for the FPGA, > =A0 =A0had better match the "hardware" exactly. =A0Literally welding the > "firmware" to the dtb makes alot of sense. > > =A0 =A0FPGA "firmware" is typically created with hardware programming > languages like Verilog, and VHDL. > =A0 =A0It is still "programmed" and like all programming quality varies. > > David Gibson wrote: >> On Mon, May 11, 2009 at 11:22:21PM -0600, Grant Likely wrote: >> >>> On Mon, May 11, 2009 at 7:12 PM, David Gibson >>> wrote: >>> >>>> On Mon, May 11, 2009 at 05:09:27PM -0600, Grant Likely wrote: >>>> >>>>> In other words; having your bootloader support FDT is preferred, but >>>>> not required. >>>>> >>>> I wouldn't even go so far as to say it's preferred. =A0IMO, people hav= e >>>> gone a bit prematurely keen on moving devtree handling into the >>>> firmware. =A0Putting it in the firmware has a number of advantages, bu= t >>>> it also has a number of non-trivial disadvantages. >>>> >>> I disagree. =A0The more I work with it, the more I appreciate the >>> advantage of decoupling the kernel image file from the hardware >>> description. =A0It is valuable being able to build a single image file >>> that boots on a wide range of boards because the device tree passed in >>> by firmware. >>> >> >> Heh, where all my work in the embedded space has led me to more and >> more appreciate the fact that firmware is almost invariably crap, and >> that it's therefore best not to trust anything it tells you. >> >> >>> I'm not downplaying the disadvantages and problems, but I still hold >>> the view that the striving for generic multiplatform kernel images is >>> worth the effort. >>> >>> ... but I do agree that hard linking the .dtb into firmware, or making >>> the .dtb hard to upgrade is the way of madness. >>> >> >> Ah, we're talking at cross purposes a bit then. =A0Yeah, I'm talking >> about the situation where the dtb is part of the firmware, or at least >> as difficult / inconvenient to update as the firmware. =A0If the dtb is >> separate from the kernel, but as easy to update / switch as the >> kernel, that is indeed a very nice setup. >> >> > > > -- > Dave Lynch =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0DLA Systems > Software Development: =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0= =A0 =A0 =A0 =A0 =A0Embedded Linux > 717.627.3770 =A0 =A0 =A0 =A0 =A0 dhlii@dlasys.net =A0 =A0 =A0 =A0 =A0 htt= p://www.dlasys.net > fax: 1.253.369.9244 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 =A0Cell: 1.717.587.7774 > Over 25 years' experience in platforms, languages, and technologies too n= umerous to list. > > "Any intelligent fool can make things bigger and more complex... It takes= a touch of genius - and a lot of courage to move in the opposite direction= ." > Albert Einstein > > --=20 Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd.