ASoC: Pin enable controls for components

Provide an interface for devices to manipulate their own pins in DAPM
without being affected by the renaming facilities provided by ASoC for
machine drivers.
ASoC: core: Add component pin control functions

It's often the case that a codec driver will need to control its
own pins. However, if a name_prefix has been applied to this codec it
must be included in the name passed to any of the snd_soc_dapm_x_pin()
functions.

The behaviour of the existing pin control functions is reasonable, since
you may want to search for a fully-specified name within the scope of an
entire card. This means that we can't apply the prefix in these functions
because it will break card-scope searches.

Constructing a prefixed string "manually" in codec drivers leads to a lot
of repetition of the same code.

To make this tidier in codec drivers this patch adds a new set of
equivalent functions that take a struct snd_soc_component instead of a
dapm context and automatically add the component's name_prefix to the
given name. This makes it a simple change in codec drivers to be
prefix-safe.

The new functions are not quite trivial enough to be inlines and the
compiler won't be able to compile-away any part of them.

Although it looks somewhat inefficient to have to allocate a temporary
buffer and combine strings, the current design of the widget list
doesn't lend itself to a more optimized implementation - it's a single
list of all widgets on a card and is searched linearly for a matching
string. As pin state changes are generally low-frequency events it's
unlikely to be a significant issue - at least not enough to rewrite the
widget list handling just for this.

Signed-off-by: Richard Fitzgerald <rf@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
2 files changed