[RFC PATCH 1/2] ASoC: soc-component: add snd_soc_component_read/write_field()

[Srinivas Kandagatla]

It's often the case that we would write or read a particular field
in register. With the current soc_component apis, reading a particular
field in register would involve first read the register and then
perform shift operations.

Ex:
to read from a field mask of 0xf0

	val = snd_soc_component_read(component, reg);
	field = ((val & 0xf0) >> 0x4);

This is sometimes prone to errors and code become less readable!

With this new api we could just do
	field = snd_soc_component_read_field(component, reg, 0xf0);

this makes it bit simple, easy to write and less error prone!

This also applies to writing!

There are various places in kernel which provides such field interfaces
however soc_component seems to be missing this.

This patch is inspired by FIELD_GET/FIELD_PREP macros in include/linux/bitfield.h

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla at linaro.org>
---
 include/sound/soc-component.h |  6 ++++
 sound/soc/soc-component.c     | 62 +++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/include/sound/soc-component.h b/include/sound/soc-component.h
index 0bce41fefd30..5b47768222b7 100644
--- a/include/sound/soc-component.h
+++ b/include/sound/soc-component.h
@@ -353,6 +353,12 @@ int snd_soc_component_test_bits(struct snd_soc_component *component,
 				unsigned int reg, unsigned int mask,
 				unsigned int value);
 
+unsigned int snd_soc_component_read_field(struct snd_soc_component *component,
+					  unsigned int reg, unsigned int mask);
+int snd_soc_component_write_field(struct snd_soc_component *component,
+				  unsigned int reg, unsigned int mask,
+				  unsigned int val);
+
 /* component wide operations */
 int snd_soc_component_set_sysclk(struct snd_soc_component *component,
 				 int clk_id, int source,
diff --git a/sound/soc/soc-component.c b/sound/soc/soc-component.c
index 760523382f3c..6bdfc6f61ed6 100644
--- a/sound/soc/soc-component.c
+++ b/sound/soc/soc-component.c
@@ -12,6 +12,7 @@
 #include <linux/pm_runtime.h>
 #include <sound/soc.h>
 
+#define __soc_component_field_shift(x) (__builtin_ffs(x) - 1)
 #define soc_component_ret(dai, ret) _soc_component_ret(dai, __func__, ret)
 static inline int _soc_component_ret(struct snd_soc_component *component,
 				     const char *func, int ret)
@@ -839,6 +840,67 @@ int snd_soc_component_update_bits_async(struct snd_soc_component *component,
 }
 EXPORT_SYMBOL_GPL(snd_soc_component_update_bits_async);
 
+/**
+ * snd_soc_component_read_field() - Read register field value
+ * @component: Component to read from
+ * @reg: Register to read
+ * @mask: mask of the register field
+ *
+ * Return: read value of register field.
+ */
+unsigned int snd_soc_component_read_field(struct snd_soc_component *component,
+					  unsigned int reg, unsigned int mask)
+{
+	unsigned int val;
+
+	mutex_lock(&component->io_mutex);
+	val = soc_component_read_no_lock(component, reg);
+	if (mask)
+		val = (val & mask) >> __soc_component_field_shift(mask);
+	mutex_unlock(&component->io_mutex);
+
+	return val;
+}
+EXPORT_SYMBOL_GPL(snd_soc_component_read_field);
+
+/**
+ * snd_soc_component_write_field() - write to register field
+ * @component: Component to write to
+ * @reg: Register to write
+ * @mask: mask of the register field to update
+ * @val: value of the field to write
+ *
+ * Return: 1 for change, otherwise 0.
+ */
+int snd_soc_component_write_field(struct snd_soc_component *component,
+				  unsigned int reg, unsigned int mask,
+				  unsigned int val)
+{
+	unsigned int old, new;
+	int ret = 0;
+	bool change;
+
+	if (!mask)
+		return false;
+
+	mutex_lock(&component->io_mutex);
+
+	old = soc_component_read_no_lock(component, reg);
+
+	val = val << __soc_component_field_shift(mask);
+
+	new = (old & ~mask) | (val & mask);
+
+	change = old != new;
+	if (change)
+		ret = soc_component_write_no_lock(component, reg, new);
+
+	mutex_unlock(&component->io_mutex);
+
+	return change;
+}
+EXPORT_SYMBOL_GPL(snd_soc_component_write_field);
+
 /**
  * snd_soc_component_async_complete() - Ensure asynchronous I/O has completed
  * @component: Component for which to wait
-- 
2.21.0