[PATCH 0/3] iio: light: tcs3472: devm conversion, wait time, locking cleanup

This series of changes modernizes the tcs3472 driver by completing the
devm conversion and updating the locking style to use an automatic
guard (mutex). Furthermore, it implement control of the WAIT state,
resolving a TODO.

Patch1: Converts the driver to use device-managed resource allocation.
This removes the need for an explicit remove() callback, since cleanup
is now handled automatically. It also adds a new function called
tcs3472_powerdown_action() that powers down the chip when the driver is 
unloaded, removed or when probe fails after the chip has been enabled.

Patch2: adds support for the wait time resolving the old TODO comment.
The user can control the WTIME indirectly by writing to the
sampling_frequency attribute. Changing the sampling
frequency attribute results in a change to the wtime while preserving
the current integration time.
Similarly, if the user has previously set a sampling frequency and
then changes the integration time, the driver re-computes WTIME so the 
previous frequency is preserved. The patch also handles the deactivation
of wtime when the requested frequency is very high, as well as the
extension of wtime to its maximum values (by enabling the use of WLONG)
when the requested frequency is very low.

Patch3: converts the remaining mutex_lock()/mutex_unlock() pairs to
guard(mutex).

All patches have been tested on a Raspberry Pi 3B with a TCS3472
connected to I2C-1 at address 0x29. Sampling frequency and integration
time changes have been exercised checking the value of WTIME and
consequently WEN and WLONG. Raw RGBC reads, calibscale, integration_time
and threshold events continue to work as before.

Aldo Conte (3):
  iio: light: tcs3472: use devm for resource management
  iio: light: tcs3472: implement wait time and sampling frequency
  iio: light: tcs3472: Use guard(mutex)() family over manual locking

 drivers/iio/light/tcs3472.c | 287 ++++++++++++++++++++++++++----------
 1 file changed, 206 insertions(+), 81 deletions(-)

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2.54.0