drivers: iio: adc: ltc2497: Rename the LTC2499 iio device

Set the iio device's name based on the chip used for the
LTC2499 only. The most common way for IIO clients to interact
with a device is to address it based on it's name. By using
the dev_name() function, the name will be set based on a
i2c_client's kobj name, which has the format i2c_instance-i2c_address
(1-0076 for example). This is not ideal, since it makes a
requirement for userspace to have knowledge about the hardware
connections of the device.

The name field is set to NULL for the LTC2497 and LTC2496, so
that the old name can kept as it is, since changing it will
result in an ABI breakage.

Signed-off-by: Ciprian Regus <ciprian.regus@analog.com>
Link: https://lore.kernel.org/r/20220916140922.2506248-6-ciprian.regus@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers: iio: adc: ltc2497: LTC2499 support

The LTC2499 is a 16-channel (eight differential), 24-bit,
ADC with Easy Drive technology and a 2-wire, I2C interface.

Implement support for the LTC2499 ADC by extending the LTC2497
driver. A new chip_info struct is added to differentiate between
chip types and resolutions when reading data from the device.

Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/2499fe.pdf
Signed-off-by: Ciprian Regus <ciprian.regus@analog.com>
Link: https://lore.kernel.org/r/20220916140922.2506248-5-ciprian.regus@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: ltc2496: Fix alignment for DMA safety

____cacheline_aligned is an insufficient guarantee for non-coherent DMA
on platforms with 128 byte cachelines above L1. Switch to the updated
IIO_DMA_MINALIGN definition.

Update the comment to include 'may'.

Fixes: e4c5c4dfaa88 ("iio: adc: new driver to support Linear technology's ltc2496")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220508175712.647246-22-jic23@kernel.org

spi: make remove callback a void function

The value returned by an spi driver's remove function is mostly ignored.
(Only an error message is printed if the value is non-zero that the
error is ignored.)

So change the prototype of the remove function to return no value. This
way driver authors are not tempted to assume that passing an error to
the upper layer is a good idea. All drivers are adapted accordingly.
There is no intended change of behaviour, all callbacks were prepared to
return 0 before.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Claudius Heine <ch@denx.de>
Acked-by: Stefan Schmidt <stefan@datenfreihafen.org>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # For MMC
Acked-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Acked-by: Łukasz Stelmach <l.stelmach@samsung.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20220123175201.34839-6-u.kleine-koenig@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>

iio:adc:ltc2496: Drop of_match_ptr and use mod_devicetable.h

The macro prevents use of driver with ACPI PRP0001 and
the of_match_id structure is defined in mod_devicetable.h so include
that directly rather than of.h.

Note this is mostly about removing something I don't want cut and
paste into new drivers rather than expectation that this particular
driver will be used on an ACPI platform.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

iio: adc: new driver to support Linear technology's ltc2496

This chip is similar to the LTC2497 ADC, it just uses SPI instead of I2C
and so has a slightly different protocol. Only the actual hardware
access is different. The spi protocol is different enough to not be able
to map the differences via a regmap.

Also generalize the entry in MAINTAINER to cover the newly introduced
file.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>