From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: Request review of device tree documentation Date: Mon, 14 Jun 2010 10:47:40 +0100 Message-ID: <20100614094740.GB7881@n2100.arm.linux.org.uk> References: <4C13B618.1030006@firmworks.com> <1276383132.1962.195.camel@pasglop> <4C146F18.9030008@firmworks.com> <1276408773.1962.574.camel@pasglop> <20100614073828.GA6095@n2100.arm.linux.org.uk> <4C15DE2E.1050905@firmworks.com> <20100614092559.GA7881@n2100.arm.linux.org.uk> <1276508170.2552.43.camel@pasglop> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1276508170.2552.43.camel@pasglop> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane.org@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane.org@lists.ozlabs.org To: Benjamin Herrenschmidt Cc: Nicolas Pitre , microblaze-uclinux@itee.uq.edu.au, devicetree-discuss , Olof Johansson , linuxppc-dev , Mitch Bradley , Dan Malek , Jeremy Kerr , linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org On Mon, Jun 14, 2010 at 07:36:10PM +1000, Benjamin Herrenschmidt wrote: > However, there's a lot of room for abuse here and I'm worried that if it > becomes widespread, we'll start seeing vendors use that as a way to do > some kind of HAL and hide various platform methods in there (clock > control, nvram, etc...). This is what I'm worried about too. As I said in my first reply in this thread, calling out from the kernel will kill performance due to the time taken to shut down the caches and MMU, which can only be done safely with all exceptions turned off. The only time that it can be seriously considered is if you're calling out to reboot, shutdown or kexec.