We no longer need the rtc compat handling to be in common code, now that
all drivers are either moved to the rtc-class framework, or (rarely)
exist in drivers/char for architectures without compat mode (m68k,
alpha and ia64, respectively).

I checked the list of ioctl commands in drivers, and the ones that are
not already handled are all compatible, again with the one exception of
m68k driver, which implements RTC_PLL_GET and RTC_PLL_SET, but has no
compat mode.

Unlike earlier versions of this patch, I'm now adding a separate
compat_ioctl handler that takes care of RTC_IRQP_READ32/RTC_IRQP_SET32
and treats all other commands as compatible, leaving the native
behavior unchanged.

The old conversion handler also deals with RTC_EPOCH_READ and
RTC_EPOCH_SET, which are not handled in rtc-dev.c but only in a single
device driver (rtc-vr41xx), so I'm adding the compat version in the same
place. I don't expect other drivers to need those commands in the future.

Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
v4: handle RTC_EPOCH_SET32 in rtc_dev_compat_ioctl
v3: handle RTC_IRQP_READ32/RTC_IRQP_SET32 in rtc_dev_compat_ioctl
v2: merge compat handler into ioctl function to avoid the
    compat_alloc_user_space() roundtrip, based on feedback
    from Al Viro.

Correct trivial checkpatch warnings, mostly whitespace issues and
unbalanced braces.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Use SPDX-License-Identifier instead of a verbose license text. Also fix the
block comment alignment.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Since commit 416f0e8056f7 ("RTC: sa1100: Update the sa1100 RTC driver."),
the last user of .read_callback is gone. It has been 8 years and now new
user appeared. Simply remove it.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Rename core files so there is a clearer separation between the RTC core and
the RTC drivers.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>