On 07/18/2012 04:54 PM, Eric Nelson wrote:
On 07/18/2012 07:11 AM, Knut Wohlrab wrote:
On 07/18/2012 03:47 PM, Jassi Brar wrote:
On 18 July 2012 15:19, Knut Wohlrab <knut.wohlrab@xxxxxxxxxxxx> wrote:
If a SD card is inserted at boot time, its "mmcblk0", the embedded
MMC (eMMC) device "mmcblk1". This makes it difficult to give the kernel the
correct device for the eMMC root file system ("root=/dev/mmcblk?p1 ...").
How about root=UUID=<eMMC-partition> ?
Because we are talking about an embedded device, it is very difficult to get a
UUID of a eMMC partition into kernel command line with U-Boot. Handling of UUID
is also a big effort at board manufacturing.
Startup speed is very important for us. Searching for UUID on several MMC/SD
devices will significant slow down the boot process.
This problem can occur on many devices with embedded MMC and removable SD, e.g.
smart phones. So I think we should find an solution to define MMC scan order or
device number/name in a device tree.
Isn't /dev/disk/by-path what you're after?
~$ ls -l /dev/disk/by-path/
lrwxrwxrwx 1 root root 13 Jan 1 15:22 platform-mmc0:b368 ->
../../mmcblk0
lrwxrwxrwx 1 root root 15 Jan 1 15:22 platform-mmc0:b368-part1
-> ../../mmcblk0p1
lrwxrwxrwx 1 root root 15 Jan 1 15:22 platform-mmc0:b368-part2
-> ../../mmcblk0p2
lrwxrwxrwx 1 root root 15 Jan 1 15:22 platform-mmc0:b368-part3
-> ../../mmcblk0p3
No, because we have to know which will be the name of the root device
_before_ we start the kernel. In our embedded device we start the kernel
with a bootloader (U-Boot) and pass the root device with the kernel
command line parameter "root=/dev/mmcblk0p1". That is not possible if we
do not know what will be the name of the root device (mmcblk0 or
mmcblk1) when kernel try to mount it.
Thanks and regards
Knut
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