rspro board and mounting root from SD

[Adrian Chadd]

Howdy,

I've been looking at using an SD card as a test root device but it
unfortunately appears that device probing doesn't quite happen fast
enough for the umass device to be enumerated.

description:

* system boots
* usbus0 is created - root_mount_hold("usbus0") called
* usbus0 is probed, and umass0 is found/createdcreated
* umass0 probe begins
* root_mount_rel() on usbus0 is called
* nothing else is waiting, so VFS tries mounting the root device

The SD probe/attach doesn't occur until -after- the root is mounted
and the system begins.

If I stick a root_mount_hold() call in umass_attach(), the umass
device is given the opportunity to complete probe/attach but obviously
then a lack of root_mount_rel() results in nothing completing.

Any ideas? My knowledge of USB/CAM internals is currently
non-existant. I couldn't find any particular function/callback which
is called when the umass bus probe completes - as far as I can tell,
attach kicks off some CAM messages which may eventually end up finding
a device or not. I'm not sure of the "right" place to put the release;
or whether I'm on the right track at all.


Adrian