K 10
svn:author
V 3
ian
K 8
svn:date
V 27
2019-07-08T20:26:56.947279Z
K 7
svn:log
V 922
Restore the ability for i2c slave devices to do IO from their probe method.

r348164 added code to iicbus_request_bus/iicbus_release_bus to automatically
call device_busy()/device_unbusy() as part of aquiring exclusive use of the
bus (so modules can't be unloaded while the bus is exclusively owned and/or
IO is in progress).  That broke the ability to do i2c IO from a slave device
probe method, because the slave isn't attached yet, so calling device_busy()
triggers a sanity-check panic for trying to busy a non-attached device.

Now we check whether the device status is < DS_ATTACHING, and if so we busy
the iicbus rather than the slave device.  I think this leaves a small window
where a module could be unloaded while probing is in progress.  But I think
that's true of all devices, and probably should be fixed by introducing a
DS_PROBING state for devices, and handling that at various points in the
newbus code.

END