iio:adc:ad_sigma_delta: Move exports into IIO_AD_SIGMA_DELTA namespace

In order to avoid unnecessary pollution of the global symbol namespace
move the core/library functions into a specific namespace and import
that into the various specific device drivers that use them.

For more information see https://lwn.net/Articles/760045/

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Renato Lui Geh <renatogeh@gmail.com>
Cc: Michael Hennerich <Michael.Hennerich@analog.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220130205701.334592-2-jic23@kernel.org

iio: adc: ad7780: Fix IRQ flag

Correct IRQ flag here is falling.

In Sigma-Delta devices the SDO line is also used as an interrupt.
Leaving IRQ on level instead of falling might trigger a sample read
when the IRQ is enabled, as the SDO line is already low. Not sure
if SDO line will always immediately go high in ad_sd_buffer_postenable
before the IRQ is enabled.

Also the datasheet seem to explicitly say the falling edge of the SDO
should be used as an interrupt:
>From the AD7780 datasheet: " The DOUT/Figure 22 RDY falling edge
can be used as an interrupt to a processor"

Fixes: da4d3d6bb9f6 ("iio: adc: ad-sigma-delta: Allow custom IRQ flags")
Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
Cc: <Stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210906065630.16325-3-alexandru.tachici@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: ad7780: convert to device-managed functions

With the devm_ad_sd_setup_buffer_and_trigger() helper, it's a bit easier
now to convert the probe of the AD7780 driver to use device-managed
functions.

Only the regulator disable requires a devm_add_action_or_reset() callback.

This change does that, cleaning up the driver a bit.

Signed-off-by: Alexandru Ardelean <aardelean@deviqon.com>
Link: https://lore.kernel.org/r/20210513120752.90074-9-aardelean@deviqon.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: ad7780: Fix a resource handling path in 'ad7780_probe()'

If 'ad7780_init_gpios()' fails, we must not release some resources that
have not been allocated yet. Return directly instead.

Fixes: 5bb30e7daf00 ("staging: iio: ad7780: move regulator to after GPIO init")
Fixes: 9085daa4abcc ("staging: iio: ad7780: add gain & filter gpio support")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Renato Lui Geh <renatogeh@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: remove explicit IIO device parent assignment

This patch applies the semantic patch:
@@
expression I, P, SP;
@@
I = devm_iio_device_alloc(P, SP);
...
- I->dev.parent = P;

It updates 302 files and does 307 deletions.
This semantic patch also removes some comments like
'/* Establish that the iio_dev is a child of the i2c device */'

But this is is only done in case where the block is left empty.

The patch does not seem to cover all cases. It looks like in some cases a
different variable is used in some cases to assign the parent, but it
points to the same reference.
In other cases, the block covered by ... may be just too big to be covered
by the semantic patch.

However, this looks pretty good as well, as it does cover a big bulk of the
drivers that should remove the parent assignment.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: ad7780: define/use own IIO channel macros

This change gets rid of the AD_SD_*_CHANNEL macros in favor of defining
it's own. The ad7780 is quite simpler than it's other Sigma-Delta brothers.

It turned out that centralizing the AD_SD_*_CHANNEL macros doesn't scale
too well, especially with some more complicated drivers. Some of the
variations in the more complicated drivers require new macros, and that way
things can become harder to maintain.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: ad-sigma-delta: Allow custom IRQ flags

Before this patch the ad_sigma_delta implementation hardcoded
the irq trigger type to low, assuming that all Sigma-Delta ADCs
have the same interrupt-type.

This patch allows all drivers using the ad_sigma_delta layer to set the
irq trigger type to the one specified in the datasheet.

Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: ad7780: Add parentheses to macros

- Fix CHECK Macro argument 'wordsize' may be better as '(wordsize)' to avoid precedence issues

Slightly modified by Jonathan to take into account the staging graduation
and a copy and paste version of the same item on the following line.

Signed-off-by: Vladimir Petrigo <vladimir.petrigo@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

staging: iio: ad7780: moving ad7780 out of staging

Move ad7780 ADC driver out of staging and into the mainline.

The ad7780 is a sigma-delta analog to digital converter. This driver provides
reading voltage values and status bits from both the ad778x and ad717x series.
Its interface also allows writing on the FILTER and GAIN GPIO pins on the
ad778x.

Signed-off-by: Renato Lui Geh <renatogeh@gmail.com>
Signed-off-by: Giuliano Belinassi <giuliano.belinassi@usp.br>
Co-developed-by: Giuliano Belinassi <giuliano.belinassi@usp.br>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>