From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sascha Hauer Subject: Re: Adding aliases to mmc Date: Sat, 21 Sep 2013 15:52:47 +0200 Message-ID: <20130921135247.GL30088@pengutronix.de> References: <5239C40C.9030503@wwwdotorg.org> <5239DC65.3080803@gmail.com> <5239DF55.8010308@wwwdotorg.org> <523A8A08.2060508@gmail.com> <523C7231.7040701@wwwdotorg.org> <523C79C4.1070308@gmail.com> <523C7FD0.3030006@wwwdotorg.org> <523D2D4F.6030802@gmail.com> <20130921074238.GI30088@pengutronix.de> <20130921123051.GN1736@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20130921123051.GN1736@pengutronix.de> Sender: linux-mmc-owner@vger.kernel.org To: Michael Olbrich Cc: Dirk Behme , Stephen Warren , Fabio Estevam , linux-mmc@vger.kernel.org, "devicetree@vger.kernel.org" , Sascha Hauer List-Id: devicetree@vger.kernel.org On Sat, Sep 21, 2013 at 02:30:51PM +0200, Michael Olbrich wrote: > Hi, > > > > > > > An embedded system typically doesn't have an initrd. The kernel > > > boots directly into the rootfs on SD/eMMC. > > > > > > >>To my understanding, the UUID is different for each SD card/eMMC, correct? > > > > > > > >Yes by default. > > > > > > > >Although for an embedded product with a fixed eMMC, there's no reason > > > >you couldn't make every device have the same UUID for the fixed device. > > > > > > How do you make the eMMC on 1000 boards have the same UUID? > > > > The same way you ensure an identical partition table in these 1000 > > boards. The disk signature is just a four byte value at offset 440 in > > the MBR. Set this to your birthday or whatever on all boards, pass > > root=PARTUUID=-01 on all boards and you're done. > > Until someone inserts a SD-Card with the same disk signature... Indeed. That would be a nice way to boot your own rootfs on otherwise locked devices ;) Sascha -- 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 |