backlight: mp3309c: Fully initialize backlight_properties during probe

props is stack allocated and, although this driver initializes all the
fields that are not "owned" by the framework, we'd still like to ensure
it is zeroed to avoid problems from this driver if the fields change.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20240220153532.76613-5-daniel.thompson@linaro.org
Signed-off-by: Lee Jones <lee@kernel.org>

backlight: mp3309c: Utilise temporary variable for struct device

We have a temporary variable to keep pointer to struct device.
Utilise it where it makes sense.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Tested-by: Flavio Suligoi <f.suligoi@asem.it>
Link: https://lore.kernel.org/r/20240208184313.2224579-4-andriy.shevchenko@linux.intel.com
Signed-off-by: Lee Jones <lee@kernel.org>

backlight: mp3309c: Use dev_err_probe() instead of dev_err()

Replace dev_err() with dev_err_probe().

This helps in simplifing code and standardizing the error output.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Flavio Suligoi <f.suligoi@asem.it>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20240208184313.2224579-3-andriy.shevchenko@linux.intel.com
Signed-off-by: Lee Jones <lee@kernel.org>

backlight: mp3309c: Make use of device properties

Convert the module to be property provider agnostic and allow
it to be used on non-OF platforms.

Add mod_devicetable.h include.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Flavio Suligoi <f.suligoi@asem.it>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20240208184313.2224579-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Lee Jones <lee@kernel.org>

backlight: mp3309c: Use pwm_apply_might_sleep()

pwm_apply_state() is deprecated since commit c748a6d77c06a ("pwm: Rename
pwm_apply_state() to pwm_apply_might_sleep()"). This is the final user
in the tree.

Signed-off-by: Sean Young <sean@mess.org>
Tested-by: Flavio Suligoi <f.suligoi@asem.it>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20240128154905.407302-1-sean@mess.org
Signed-off-by: Lee Jones <lee@kernel.org>

backlight: mp3309c: Fix uninitialized local variable

In the function "pm3309c_parse_dt_node", when the dimming analog control
mode (by I2C messages) is enabled, the local variable "prop_levels" is
tested without any initialization, as indicated by the following smatch
warning:

drivers/video/backlight/mp3309c.c:279 pm3309c_parse_dt_node() error: uninitialized symbol 'prop_levels'.

To avoid any problem in case of undefined behavior, we need to initialize
it to "NULL".

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/dri-devel/af0a1870-693b-442f-9b11-0503cfcd944a@moroto.mountain/
Fixes: 2e914516a58c ("backlight: mp3309c: Add support for MPS MP3309C")
Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20231129164514.2772719-1-f.suligoi@asem.it
Signed-off-by: Lee Jones <lee@kernel.org>

backlight: mp3309c: Add support for MPS MP3309C

The Monolithic Power (MPS) MP3309C is a WLED step-up converter, featuring a
programmable switching frequency to optimize efficiency.
The brightness can be controlled either by I2C commands (called "analog"
mode) or by a PWM input signal (PWM mode).
This driver supports both modes.

For DT configuration details, please refer to:
- Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml

The datasheet is available at:
- https://www.monolithicpower.com/en/mp3309c.html

Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20231116105319.957600-3-f.suligoi@asem.it
Signed-off-by: Lee Jones <lee@kernel.org>