On 05/23/2014 02:29 AM, Michael Olbrich wrote: > On Thu, May 22, 2014 at 01:23:27PM -0600, Stephen Warren wrote: >> On 05/22/2014 12:21 PM, Sascha Hauer wrote: >>> On Thu, May 22, 2014 at 10:16:35AM -0600, Stephen Warren wrote: >>>> On 05/22/2014 09:30 AM, Sascha Hauer wrote: >>>>> Hi all, >>>>> >>>>> The wish to have persistent MMC block device names for passing a suitable >>>>> root=/dev/mmcblkX option came up several times already and has been discussed >>>>> at least in these threads: >>>>> >>>>> http://lists.infradead.org/pipermail/linux-arm-kernel/2012-July/109984.html >>>>> https://www.mail-archive.com/linux-mmc@xxxxxxxxxxxxxxx/msg22104.html >>>>> http://comments.gmane.org/gmane.linux.kernel.mmc/21519 >>>>> >>>>> Several patches have been proposed to nail the slot index to a known number. >>>>> Arguments against these patches were: >>>>> >>>>> - Use an initrd and locate the correct root device there >>>>> even Thomas who suggested this admitted this would be painful to do >>>>> - use root=UUID= or root=PARTUUID= >>>>> This generally works but has an important downside. With the UUID >>>>> approach devices which should boot from the internal eMMC may start >>>>> booting from an external SD slot when somebody deliberately inserts >>>>> a SD card with the same UUID. >>>>> >>>>> The following patches should have the technical issues fixed. It works >>>>> by counting the mmc aliases in the devicetree during initialization of >>>>> the mmc framework. Those slot numbers will never be assigned to other >>>>> hosts. >>>> >>>> Does it solve the following, which AFAIK has always been the primary >>>> argument against aligning block device IDs with controller IDs: >>>> >>>> - User inserts SD card into MMC controller ID (or alias) 1. >>>> - /dev/mmcblk1 now exists >>>> - Mount /dev/mmcblk1 on /mnt/tmp >>>> - User removes that SD card >>>> - /dev/mmcblk1 still exists, since it's mounted so can't be deleted >>>> after the card removal. >>>> - User inserts SD card into MMC controller ID (or alias) 1. >>>> - /dev/mmcblkN (N is something other than 1) now exists >>>> >>>> Now, the block device ID must be != the original ID, since two block >>>> devices exist. > > We could limit this to non-removable devices. This problem cannot occur > there. Would that be acceptable? That might work. -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
