Add a function to read a processed value from a channel. The function will first
attempt to read the IIO_CHAN_INFO_PROCESSED attribute. If that fails it will
read the IIO_CHAN_INFO_RAW attribute and convert the result from a raw value to
a processed value.

The patch also introduces a function to convert raw value to a processed value
and exports it, in case a user needs or wants to do the conversion by itself.
Signed-off-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

For the iio_read_channel_raw and iio_read_channel_scale the kerneldoc comment
refers to an argument called "channel", while the argument is called "chan" in
the function signature. This leads to the following warnings from kerneldoc:

	Warning(include/linux/iio/consumer.h:71): No description found for parameter 'chan'
	Warning(include/linux/iio/consumer.h:71): Excess function parameter 'channel' description in 'iio_read_channel_raw'
	Warning(include/linux/iio/consumer.h:109): No description found for parameter 'chan'
	Warning(include/linux/iio/consumer.h:109): Excess function parameter 'channel' description in 'iio_read_channel_scale'

This patch fixes the warnings by naming them consistently.
Signed-off-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

The symbol name for the #ifndef and the #define of the include guard do not
match and thus it becomes quite ineffective. Add the missing '_' to fix this.
Signed-off-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

These were originally introduced when the plan was to have parallel
IIO cores in and out of staging with a slow move between them.
Now we have reached the point where the whole core has moved,
they need clearing up!
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

Step 1 in moving the IIO core out of staging.
Signed-off-by: NJonathan Cameron <jic23@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Lifted from proposal for in kernel interface built on the out of staging
branch.

Two elements here:
* Map as defined in "inkern.h"
* Matching code to actually get the iio_dev and channel
that we want from the global list of IIO devices.
V4: Everything now built if iio is built (rather than being optional)
    Removal race condition prevented by using info pointer as a check
    of removal under a lock.
V3: Drop the option of registering / getting channels using dev pointer.
Stick to name only as suggested by Mark Brown (this has caused user
confusion in the regulator framework.)
V2: As per Greg KH suggestion, move over to registration by passing
the tables into the provider drivers (how regulator does it).
This does not prevent us using the original more flexible approach
if at a later date there is a usecase that demands it.
Signed-off-by: NJonathan Cameron <jic23@kernel.org>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>