On Fri, Apr 29, 2016 at 12:43:39PM -0700, Doug Anderson wrote: > Russell, > > On Fri, Apr 29, 2016 at 11:12 AM, Russell King - ARM Linux > <linux@xxxxxxxxxxxxxxxx> wrote: > > On Fri, Apr 29, 2016 at 10:32:15AM -0700, Douglas Anderson wrote: > >> This series picks patches from various different places to produce what > >> I consider the best solution to getting consistent mmc and mmcblk > >> ordering. > >> > >> Why consistent ordering and why not just use UUIDs? IMHO consistent > >> ordering solves a few different problems: > > > > NAK. Really. Use UUIDs, that's the proper solution here. > > Un-NAK. UUIDs don't solve point #1. Re-NAK. I don't think your point #1 is valid. See my other reply. > * Presumably on a PC you've got an extra bit in the middle (like grub > or something like that) that can help you resolve your UUIDs even if > you get your kernel from somewhere else. You are over-estimating what grub does. Grub doesn't resolve UUIDs at all. Grub just passes the kernel arguments in its configuration file for the entry it is booting to the kernel. It's a static configuration found in /boot/grub/grub.conf. It doesn't probe devices for UUIDs. > * Presumably in the non-embedded world kernel hackers have a different > workflow. They probably don't swap between different devices with > different configurations on an hourly basis. They're not in the habit > of totally reimaging their system periodically. Etc. Trying to force > the workflow of a PC kernel hacker and an embedded kernel hacker to be > the same doesn't seem like a worthwhile goal. In _my_ world with the "embedded" devices I have, I mount by UUID on platforms which have multiple MMC devices to avoid exactly the problem you're having. This works fine. If I were to switch the SD card, and I wanted to avoid changing the boot loader configuration, I'd use label instead, and I'd label all the SD card rootfs using the same label so I could just swap the cards. > * Presumably an embedded kernel hacker running with ATA / SCSI could > _usually_ assume that "sda" is his/her root filesystem. It's unlikely > an embedded system would have more than one "sda" disk builtin and > it's nearly guaranteed (I think) that a builtin ATA / SCSI controller > would probe before any USB based devices. You've got a funny view again. N2100 has two hard disks. The clearfog board from SolidRun has two mini-PCIe slots, each of which can have two SATA interfaces... If you want to use it as a server-type platform with lots of disks... > Sure, if your root > filesystem is USB based (really?) and you've got additional USB > storage devices then you're SOL. Sorry. One of my Versatile Express platforms boots from USB, and has a MMC slot... So this argument does not stack up. Sorry. -- RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
