specifying order of /dev/mmcblk devices via device-tree?

Hello Tim,

On Fri, Oct 28, 2016 at 12:23 PM, Tim Harvey [off-list ref] wrote:

Greetings,

I have an IMX6 board that has the following:
sdhc1: mmc0: sdio radio
sdhc2: mmc1: /dev/mmcblk1: microSD connector
sdhc3: mmc2: /dev/mmcblk2: on-board eMMC

I would like to have sdhc3 registered as /dev/mmcblk0 and sdhc2
registered as /dev/mmcblk1 so that permanent storage is the first
mmcblk device as I think this is more intuitive however currently
these get instanced in the order they appear in the imx6qdl.dtsi
device-tree configuration and are not able to be mapped the way I want
them in my dts file.

One should not rely on a specific MMC block device numbering, since
this could change. Look at commit 9aaf3437aa72 ("mmc: block: Use the
mmc host device index as the mmcblk device index").

Is there a way, or if not is there a desire for a way, to specify the
order of /dev/mmcblk devices via device-tree?

There was an attempt to use aliasses for this but got nacked:

https://lkml.org/lkml/2016/4/29/610

As Fabio said, you should either use UUID or labels instead:

https://wiki.archlinux.org/index.php/persistent_block_device_naming

Regards,

Tim

Best regards,
Javier