From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from metis.ext.pengutronix.de ([92.198.50.35]:33632 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753397Ab3GZIKE (ORCPT ); Fri, 26 Jul 2013 04:10:04 -0400 Date: Fri, 26 Jul 2013 10:09:53 +0200 From: Steffen Trumtrar Subject: Re: [RFC 0/2] Set mmc(blk)X with DT alias Message-ID: <20130726080953.GA2118@pengutronix.de> References: <1374656973-16250-1-git-send-email-s.trumtrar@pengutronix.de> <51F16046.3020809@wwwdotorg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51F16046.3020809@wwwdotorg.org> Sender: devicetree-owner@vger.kernel.org To: Stephen Warren Cc: linux-mmc@vger.kernel.org, Chris Ball , devicetree@vger.kernel.org, kernel@pengutronix.de List-ID: On Thu, Jul 25, 2013 at 10:28:38AM -0700, Stephen Warren wrote: > On 07/24/2013 02:09 AM, Steffen Trumtrar wrote: > > Hi! > > > > Embedded devices often use multiple SD/MMC devices as boot/rootfs disks. > > Some of them are removable, some not. If the removable cards are not > > present, but are probed before the non-removable ones, the indexing > > scheme changes. This makes it harder to hard-code the rootfs in the > > cmdline. > > > > First solution I came up with was the alias-node in DT. > > I guess my implementation is pretty hacky and ugly, but you can get lost > > pretty fast in the whole mmc stack. > > For example, the second patch should use "card->host->index" instead of parsing > > the alias again, I guess. I'm not sure why it currently doesn't though. > > This has been discussed a few times before and rejected IIRC. One issue > is that block device ID is actually decoupled from host controller ID > anyway, e.g. if a removable device is mounted, removed, and then > re-plugged the new device can get a different ID, so this approach > doesn't really work in all cases anyway. > Hm, okay. I actually wasn't aware of the older discussions. > > So, if there is a better place or solution to specify a reliable ordering > > of mmc devices, please let me hear it. > > root=UUID=xxx or root=PARTUUID=xxx are the best solution. With recent > U-Boot, you can enable and use the "part" command to find the partition > UUID automatically, and hence not need to hard-code anything. Something > similar could presumably be implemented for other bootloaders. I am actually okay with that. I know barebox can do that, but didn't knew that U-Boot is also capabable of that. So, I'm okay with dropping the patch. Thanks, Steffen -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |