[REGRESSION] 6.6.141 s390x build failure in s390/cio due to missing driver_override infrastructure

[Natanael Copa]

This reports a regression in the 6.6.y stable series.

Last known good: v6.6.140
First bad: v6.6.141

On s390x, v6.6.141 fails to build in drivers/s390/cio/css.c after the
backport of:

  ac4d8bb6e2e13e8684a76ea48d13ebaaaf5c24c4 ("s390/cio: use generic driver_override infrastructure")

which is present in 6.6.141 as:

  c4295487124f ("s390/cio: use generic driver_override infrastructure")

The failure is:

  drivers/s390/cio/css.c:1329:15: error: implicit declaration of function 'device_match_driver_override' [-Werror=implicit-function-declaration]
  drivers/s390/cio/css.c:1387:10: error: 'struct bus_type' has no member named 'driver_override'

This backport appears to depend on newer driver-core infrastructure that
is not present in 6.6.y, in particular:

  cb3d1049f4ea ("driver core: generalize driver_override in struct device")
  stable backport: da332e7ecbb3

In other words, the s390/cio conversion was backported without the
driver-core support it requires.

I verified the source tree version with:

  make -s kernelversion
  => 6.6.141

A minimal fix for 6.6.y seems to be reverting ac4d8bb6e2e13e8684a76ea48d13ebaaaf5c24c4.
An alternative would be a small s390/cio-specific locking fix that avoids
depending on the newer driver-core APIs.

#regzbot introduced: v6.6.140..v6.6.141
#regzbot title: s390x build failure in 6.6.141 due to incomplete s390/cio driver_override backport