From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-in-01.arcor-online.net (mail-in-01.arcor-online.net [151.189.21.41]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mx.arcor.de", Issuer "Thawte Premium Server CA" (verified OK)) by ozlabs.org (Postfix) with ESMTP id B2658DDEC6 for ; Tue, 27 Feb 2007 01:26:53 +1100 (EST) In-Reply-To: <20070226130837.GA32080@localhost.localdomain> References: <20070222011811.GA18364@localhost.localdomain> <45b623f395654fc4f4920b9553794def@kernel.crashing.org> <20070222103410.GB11014@localhost.localdomain> <9696D7A991D0824DBA8DFAC74A9C5FA302A592C7@az33exm25.fsl.freescale.net> <259dc2545888e6588a8a0707ad2e84b0@kernel.crashing.org> <9696D7A991D0824DBA8DFAC74A9C5FA302A59732@az33exm25.fsl.freescale.net> <1172299259.1902.22.camel@localhost.localdomain> <20070226041646.GC29826@localhost.localdomain> <4540139ce9bb2426dbcc3822e6c1a63a@kernel.crashing.org> <20070226130837.GA32080@localhost.localdomain> Mime-Version: 1.0 (Apple Message framework v623) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: From: Segher Boessenkool Subject: Re: [PATCH] powerpc: document new interrupt-array property Date: Mon, 26 Feb 2007 15:26:38 +0100 To: David Gibson Cc: linuxppc-dev@ozlabs.org, paulus@samba.org, Yoder Stuart-B08248 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , >> Incorrect parsing of interrupt info tends to end up >> in spectacular crashes, not silent at all ;-) > > Well, yes, but "sorry, I can't understand this device tree" or "huh? > I can't find the interrupts" would be preferable to spectacular > crashes. Yes, of course. It sometimes just can't be helped though. Oh btw, since Linux has the new interrupt mapping code, you quite probably will *not* hard crash, the kernel notices the interrupt map isn't sane and uses a fallback. You can get unlucky of course. Also, and this is just an inherent problem to all interrupts, many important devices just don't work without correctly configured interrupts (or their Linux drivers don't). With ATA at least you still get one block through every 30s, but that is hardly optimal ;-) >> You cannot boot a client program that doesn't understand the >> device tree and expect it to understand the device tree ;-) > > Obviously, but I'd like the client program to *know* that it doesn't > understand the device tree. Solving that would be equivalent to the halting problem I'm afraid. It can be done for *simple* cases of course. > It's not specific to the kernel, the same reasoning applies to any > program using the device tree. If something that's not aware of the > new property sees a node with an 'interrupts' but no > 'interrupt-parent' property, it has *no reason* to believe there's > anything more to know. And if a program parsing the device tree sees no valid "interrupts" property, it can validly assume the device doesn't have interrupts. Same problem. All of this can be avoided by just not defining a new binding for something as fundamental as interrupt mapping. Segher