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

So, someone merged a patch which makes mmcblk devices follow the
host controller numbering.

Now my cubox-i fails to boot correctly because the SD card in the
_only_ SD card slot now gets called "mmcblk1" and not "mmcblk0".

USDHC1 is wired to the on-microsom WiFi, and never has anything
remotely near a SD card or eMMC present.  So, this change is
confusing on these platforms.

Moreover, this is _going_ to break SolidRun distros if people upgrade
their kernels.

It may be appropriate for eMMC, but it's not appropriate everywhere.

This is a user visible _regression_ in 4.9-rc.  Whoever did this,
please revert whatever change caused this, and next time limit it
to only eMMC.

Thanks.

On Fri, Oct 28, 2016 at 09:45:00AM -0700, Tim Harvey wrote:

On Fri, Oct 28, 2016 at 8:37 AM, Mark Rutland [off-list ref] wrote:

quoted

On Fri, Oct 28, 2016 at 08:23:04AM -0700, Tim Harvey wrote:

quoted

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.

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?

As with many other devices, there is no standard way of controlling the
Linux enumeration (and given the ID space is shared with other dynamic
devices it's not something that could generally work).

These should be refererd to by UUID if possible.

If not, we could cosider adding a by-dt-path or something like that.

Thanks,
Mark.

Mark / Javier/ Fabio,

Thanks - this is very useful.

Yes, I agree that using UUID's is the way to go and now I see how that
can be easily accessed via uboot 'part' command.

Regards,

Tim

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