Merge tag 'y2038-alsa-v8-signed' of git://git.kernel.org:/pub/scm/linux/kernel/git...

Merge tag 'y2038-alsa-v8-signed' of git://git.kernel.org:/pub/scm/linux/kernel/git/arnd/playground into for-next

ALSA: Fix year 2038 issue for sound subsystem

This is a series I worked on with Baolin in 2017 and 2018, but we
never quite managed to finish up the last pieces. During the
ALSA developer meetup at ELC-E 2018 in Edinburgh, a decision was
made to go with this approach for keeping best compatibility
with existing source code, and then I failed to follow up by
resending the patches.

Now I have patches for all remaining time_t uses in the kernel,
so it's absolutely time to revisit them. I have done more
review of the patches myself and found a couple of minor issues
that I have fixed up, otherwise the series is still the same as
before.

Conceptually, the idea of these patches is:

- 64-bit applications should see no changes at all, neither
  compile-time nor run-time.

- 32-bit code compiled with a 64-bit time_t currently
  does not work with ALSA, and requires kernel changes and/or
  sound/asound.h changes

- Most 32-bit code using these interfaces will work correctly
  on a modified kernel, with or without the uapi header changes.

- 32-bit code using SNDRV_TIMER_IOCTL_TREAD requires the
  updated header file for 64-bit time_t support

- 32-bit i386 user space with 64-bit time_t is broken for
  SNDRV_PCM_IOCTL_STATUS, SNDRV_RAWMIDI_IOCTL_STATUS and
  SNDRV_PCM_IOCTL_SYNC_PTR because of i386 alignment. This is also
  addressed by the updated uapi header.

- PCM mmap is currently supported on native x86 kernels
  (both 32-bit and 64-bit) but not for compat mode. This series breaks
  the 32-bit native mmap support for 32-bit time_t, but instead allows
  it for 64-bit time_t on both native and compat kernels. This seems to
  be the best trade-off, as mmap support is optional already, and most
  32-bit code runs in compat mode anyway.

- I've tried to avoid breaking compilation of 32-bit code
  as much as possible. Anything that does break however is likely code
  that is already broken on 64-bit time_t and needs source changes to
  fix them.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git y2038-alsa-v8
[2] https://lore.kernel.org/lkml/CAK8P3a2Os66+iwQYf97qh05W2JP8rmWao8zmKoHiXqVHvyYAJA@mail.gmail.com/T/#m6519cb07cfda08adf1dedea6596bb98892b4d5dc

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Changes since v7: (Arnd):
 - Fix a typo found by Ben Hutchings

Changes since v6: (Arnd):
 - Add a patch to update the API versions
 - Hide a timespec reference in #ifndef __KERNEL__ to remove the
   last reference to time_t
 - Use a more readable way to do padding and describe it in the
   changelog
 - Rebase to linux-5.5-rc1, changing include/sound/soc-component.h
   and sound/drivers/aloop.c as needed.

Changes since v5 (Arnd):
 - Rebased to linux-5.4-rc4
 - Updated to completely remove timespec and time_t references from alsa
 - found and fixed a few bugs

Changes since v4 (Baolin):
 - Add patch 5 to change trigger_tstamp member of struct snd_pcm_runtime.
 - Add patch 8 to change internal timespec.
 - Add more explanation in commit message.
 - Use ktime_get_real_ts64() in patch 6.
 - Split common code out into a separate function in patch 6.
 - Fix tu->tread bug in patch 6 and remove #if __BITS_PER_LONG == 64 macro.

Changes since v3:
 - Move struct snd_pcm_status32 to pcm.h file.
 - Modify comments and commit message.
 - Add new patch2 ~ patch6.

Changes since v2:
 - Renamed all structures to make clear.
 - Remove CONFIG_X86_X32 macro and introduced new compat_snd_pcm_status64_x86_32.

Changes since v1:
 - Add one macro for struct snd_pcm_status_32 which only active in 32bits kernel.
 - Convert pcm_compat.c to use struct snd_pcm_status_64.
 - Convert pcm_native.c to use struct snd_pcm_status_64.