Re: [PATCH] gpio: add a userspace chardev ABI for GPIOs

[Greg Ungerer <gerg@uclinux.org>]

Hi Linus,

Commit 3c702e99 ("gpio: add a userspace chardev ABI for GPIOs")
breaks booting on all my m68k/ColdFire platforms (with MMU and
without). They all hang during the boot up, the last console
trace is:

  ...
  NR_IRQS:256
\x01  clocksource: pit: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1467848399018 ns
\x01  Calibrating delay loop... 1042.02 BogoMIPS (lpj=5210112)
\x01  pid_max: default: 32768 minimum: 301
\x01  Mount-cache hash table entries: 2048 (order: 0, 8192 bytes)
\x01  Mountpoint-cache hash table entries: 2048 (order: 0, 8192 bytes)

I traced this back to gpiochip_add_data() when it does the
device_add() call. On my platforms this is being called 
before gpiolib_dev_init(), and this seems to be the issue.
So gpio_bus_type has not been registered as a bus yet.

The lowest level ColdFire gpio code (arch/m68k/coldfire/gpio.c)
calls its setup from core_initcall() - and this will call
gpiochip_add_data(). This is being called first, before
the core_initcall() for gpiolib_dev_init().

I can fix by changing the core_initcall() in coldfire/gpio.c
to something like postcore_initcall() and that fixes the boot
problem.

What do you think?
Would you expect that all callers of gpiochip_add_data()
should be after core_initcall()?

Regards
Greg