From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Date: Mon, 11 Aug 2014 10:53:30 -0600 Subject: [U-Boot] [PATCH 1/3] config: introduce a generic $bootcmd In-Reply-To: <53E7A3A2.80707@myspectrum.nl> References: <1406759836-556-1-git-send-email-swarren@wwwdotorg.org> <53E25145.2090706@wwwdotorg.org> <53E4F400.6060508@wwwdotorg.org> <53E63816.60703@redhat.com> <53E6A3FE.6080807@myspectrum.nl> <53E6E2D0.7090303@wwwdotorg.org> <53E7A3A2.80707@myspectrum.nl> Message-ID: <53E8F50A.1060606@wwwdotorg.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 08/10/2014 10:53 AM, Jeroen Hofstee wrote: > Hello Stephan, > > On 10-08-14 05:11, Stephen Warren wrote: >> The entire point of this series is to prevent distros from having to >> install bootloader-specific boot configuration files. > > I fail to see why this is something to pursue. Since the distro knows > the boot path, why should u-boot be polling all possible options? This patch series allows U-Boot to find the OS and boot it. U-Boot is searching for some kind of boot configuration file. This part of the process is the same as the BIOS searching all known possible boot devices for a partition marked bootable, and with a valid MBR. Or, it's the same as UEFI searching all possible boot devices for whatever config file or boot binary is mandated by UEFI. U-Boot performs this searching before having any knowledge of the OS; there's no way for the OS to parameterize this search path, just like OSs don't configure a PC BIOS to search a specific HDD/floppy/CDROM for the MBR to boot. Once U-Boot locates extlinux.conf or boot.scr, that file encodes what files (kernel, DTB, initrd) to load to boot the OS, what kernel command-line to use, etc. This configuration file or script is written by the OS, and is where knowledge such as root filesystem identity may be encoded.