From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolas Pitre Subject: Re: Pinmux with device tree Date: Thu, 19 May 2011 22:23:12 -0400 (EDT) Message-ID: References: <4DD41F02.4050108@firmworks.com> <20110519171029.GH3085@ponder.secretlab.ca> <4DD576BD.7090307@firmworks.com> <4DD5839C.2020809@firmworks.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-reply-to: <4DD5839C.2020809-D5eQfiDGL7eakBO8gow8eQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org To: Mitch Bradley Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org List-Id: devicetree@vger.kernel.org On Thu, 19 May 2011, Mitch Bradley wrote: > On 5/19/2011 10:36 AM, Nicolas Pitre wrote: > > On Thu, 19 May 2011, Mitch Bradley wrote: > > > > > So, in my world, space is always an issue. > > > > I'm guessing that in such a scenario you have the kernel stored > > somewhere else, right? You therefore simply have to store the FDT data > > along with the kernel in that other location, and have your boot > > firmware load an additional and relatively small file. > > There is no stored FDT. The firmware generates the device tree dynamically > from a combination of static information and dynamic probing. > > > > > It is very important that the DT data be updateable independently from > > the firmware, just like the kernel is. Ideally, the DT would indeed be > > exported by the firmware, but that works only in theory. In practice it > > _will_ contain bugs that might be visible only after kernel development > > has progressed, and therefore it is primordial to be able to update it > > easily. Hence in practice it is best if it is not exported/generated by > > the firmware directly. > > > In our world it works in practice. We control the hardware, firmware, and OS > releases. In many cases, a firmware update is less expensive than an OS > release by several orders of magnitude. I don't think this can be said for ARM in general though. This is where all the recent surge of activity around DT comes from. Nicolas