Many regulators support a bypass mode where they simply switch their
input supply to the output. This is mainly used in low power retention
states where power consumption is extremely low so higher voltage or
less clean supplies can be used.

Support this by providing ops for the drivers and a consumer API which
allows the device to be put into bypass mode if all consumers enable it
and the machine enables permission for this.

This is not supported as a mode since the existing modes are rarely used
due to fuzzy definition and mostly redundant with modern hardware which is
able to respond promptly to load changes.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Reviewed-by: Graeme Gregory <gg@slimlogic.co.uk>

Based on previous LKML discussions:

 * Update docs for regulator sysfs class attributes to highlight
   the fact that all current attributes are intended to be control
   inputs, including notably "state" and "opmode" which previously
   implied otherwise.

 * Define a new regulator driver get_status() method, which is the
   first method reporting regulator outputs instead of inputs.
   It can report on/off and error status; or instead of simply
   "on", report the actual operating mode.

For the moment, this is a sysfs-only interface, not accessible to
regulator clients.  Such clients can use the current notification
interfaces to detect errors, if the regulator reports them.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

Clean up the sysfs interface to regulators by only exposing the
attributes that can be properly displayed.  For example: when a
particular regulator method is needed to display the value, only
create that attribute when that method exists.

This cleaned-up interface is much more comprehensible.  Most
regulators only support a subset of the possible methods, so
often more than half the attributes would be meaningless.  Many
"not defined" values are no longer necessary.  (But handling
of out-of-range values still looks a bit iffy.)

Documentation is updated to reflect that few of the attributes
are *always* present, and to briefly explain why a regulator may
not have a given attribute.

This adds object code, about a dozen bytes more than was removed
by the preceding patch, but saves a bunch of per-regulator data
associated with the now-removed attributes.  So there's a net
reduction in memory footprint.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

Provide a new file 'name' in the regulator sysfs class with a human
readable name for the regulator for use in applications.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

Additionally added another web resource for voltage regulators.

Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

This adds documentation describing the sysfs ABI used by the regulator
framework.

Signed-off-by: Liam Girdwood <lg@opensource.wolfsonmicro.com>