From mboxrd@z Thu Jan 1 00:00:00 1970 From: "M. Warner Losh" Subject: Re: [RFC PATCH 13/14] ARM: vexpress: Definition of vexpress dts specification Date: Fri, 20 Aug 2010 15:03:36 -0600 (MDT) Message-ID: <20100820.150336.619446192412742106.imp@bsdimp.com> References: <977313260285850582@unknownmsgid> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org To: grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org Cc: linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org, nico-vtqb6HGKxmzR7s880joybQ@public.gmane.org, Catalin.Marinas-5wv7dgnIgG8@public.gmane.org, devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, Philippe.Robin-5wv7dgnIgG8@public.gmane.org, jeremy.kerr-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org List-Id: devicetree@vger.kernel.org In message: Grant Likely writes: : Regardless though, the linux mapping doesn't actually have any bearing : on the device tree because the mapping from HW to linux irq number is : all internal to the kernel. The kernel could choose to start the : mapping at 42 or somewhere else and it would all still work. Some (all?) PowerPC platforms start their interrupt numbering at 16, since interrupts 0-15 are reserved for old-school ISA interrupts from the Super I/O chip that may (or may not) be present on these systems. It's all handled inside the kernel, so is invisible to the device-tree, as Grant is saying. Also, more OSes than Linux use device trees, so hard-coding Linux IRQ numbers would be displeasing from that point of view. Just to give one concrete example. Warner