Driver Core: don't oops with unregistered driver in driver_find_device()
authorHiroshi DOYU <hdoyu@nvidia.com>
Fri, 11 May 2012 08:03:09 +0000 (11:03 +0300)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 14 May 2012 15:46:01 +0000 (08:46 -0700)
commit094e47e9fa79e28f0e51e37400ea6eea35a4ee1f
treedb1beb67a3d074f9c40f7ca71611f334566678e1
parent3ce9a7c0ac28561567fadedf1a99272e4970f740
Driver Core: don't oops with unregistered driver in driver_find_device()

driver_find_device() can be called with an unregistered driver. Need
to check driver_private to see if it's populated or not, especially
under deferrable probe.

In the case that there are 2 drivers, one depends on the other. With
-EPROBE_DEFER, two drivers can use deferred probe to ensure that their
relative probe order doesn't matter. If dependee driver is probed
first, then the dependant's driver_find_device('dependee')
succeeds. If the dependant is probed first, then the dependant's
driver_find_device('dependee') should return NULL, and the dependant
should get -EPROBE_DEFER. driver_find_device() needs to return NULL if
it's not populated.

In [PATCHv5 2/3] ARM: tegra: Add SMMU enabler in AHB:
  http://article.gmane.org/gmane.linux.ports.tegra/4658

"tegra_ahb_driver" may not be populated when it's called.

For more SMMU/AHB specific discussion, refer to the following thread:
  https://lkml.org/lkml/2012/5/10/21

Signed-off-by: Hiroshi DOYU <hdoyu@nvidia.com>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/base/driver.c