char: broadcom: Add vcio module

Add module for accessing the mailbox property channel through
/dev/vcio. Was previously in bcm2708-vcio.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>

char: vcio: Add compat ioctl handling

There was no compat ioctl handler, so 32 bit userspace on a
64 bit kernel failed as IOCTL_MBOX_PROPERTY used the size
of char*.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>

char: vcio: Fail probe if rpi_firmware is not found.

Device Tree is now the only supported config mechanism, therefore
uncomment the block of code that fails the probe if the
firmware node can't be found.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>

drivers: char: vcio: Use common compat header

The definition of compat_ptr is now common for most platforms, but
requires the inclusion of <linux/compat.h>.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

char: vcio: Rewrite as a firmware node child

The old vcio driver is a simple character device that manually locates
the firmware driver. Initialising it before the firmware driver causes
a failure, and no retries are attempted.

Rewrite vcio as a platform driver that depends on a DT node for its
instantiation and the location of the firmware driver, making use of
the miscdevice framework to reduce the code size.

N.B. Using miscdevice changes the udev SUBSYSTEM string, so a change
to the companion udev rule is required in order to continue to set
the correct device permissions, e.g.:

    KERNEL="vcio", GROUP="video", MODE="0660"

See: https://github.com/raspberrypi/linux/issues/4620



Signed-off-by: Phil Elwell <phil@raspberrypi.com>