[PATCH v1 3/4] ASoC: tda7802: Add enable device attribute

[Thomas Preston <thomas.preston@codethink.co.uk>]

Add a device attribute to control the enable regulator. Write 1 to
enable, 0 to disable (ref-count minus one), or -1 to force disable the
physical pin.

To disable a set of amplifiers wired to the same enable gpio, each
device must be disabled. For example:

	echo 0 > /sys/devices/.../device:00/enable
	echo 0 > /sys/devices/.../device:01/enable

In an emergency, we can force disable from any device:

	echo -1 > /sys/devices/.../device:00/enable

Signed-off-by: Thomas Preston <thomas.preston@codethink.co.uk>
Cc: Patrick Glaser <pglaser@tesla.com>
Cc: Rob Duncan <rduncan@tesla.com>
Cc: Nate Case <ncase@tesla.com>
---
 sound/soc/codecs/tda7802.c | 65 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 64 insertions(+), 1 deletion(-)

diff --git a/sound/soc/codecs/tda7802.c b/sound/soc/codecs/tda7802.c
index 38ca52de85f0..62aae011d9f1 100644
--- a/sound/soc/codecs/tda7802.c
+++ b/sound/soc/codecs/tda7802.c
@@ -458,6 +458,42 @@ static struct snd_soc_dai_driver tda7802_dai_driver = {
 	.ops = &tda7802_dai_ops,
 };
 
+static ssize_t enable_show(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	struct tda7802_priv *tda7802 = dev_get_drvdata(dev);
+	int enabled = regulator_is_enabled(tda7802->enable_reg) ? 1 : 0;
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", enabled);
+}
+
+static ssize_t enable_store(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct tda7802_priv *tda7802 = dev_get_drvdata(dev);
+	int err;
+
+	if (sysfs_streq(buf, "1")) {
+		err = regulator_enable(tda7802->enable_reg);
+		if (err < 0)
+			dev_err(dev, "Could not enable (sysfs)\n");
+	} else if (sysfs_streq(buf, "0")) {
+		err = regulator_disable(tda7802->enable_reg);
+		if (err < 0)
+			dev_err(dev, "Could not disable (sysfs)\n");
+	} else if (sysfs_streq(buf, "-1")) {
+		err = regulator_force_disable(tda7802->enable_reg);
+		if (err < 0)
+			dev_err(dev, "Could not force disable (sysfs)\n");
+	} else {
+		return -EINVAL;
+	}
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(enable);
+
 /* read device tree or ACPI properties from device */
 static int tda7802_read_properties(struct tda7802_priv *tda7802)
 {
@@ -493,7 +529,34 @@ static int tda7802_read_properties(struct tda7802_priv *tda7802)
 	return err;
 }
 
-static const struct snd_soc_component_driver tda7802_component_driver;
+static int tda7802_probe(struct snd_soc_component *component)
+{
+	struct tda7802_priv *tda7802 = snd_soc_component_get_drvdata(component);
+	struct device *dev = &tda7802->i2c->dev;
+	int err;
+
+	dev_dbg(dev, "%s\n", __func__);
+
+	err = device_create_file(dev, &dev_attr_enable);
+	if (err < 0) {
+		dev_err(dev, "Could not create enable attr\n");
+		return err;
+	}
+
+	return err;
+}
+
+static void tda7802_remove(struct snd_soc_component *component)
+{
+	struct tda7802_priv *tda7802 = snd_soc_component_get_drvdata(component);
+
+	device_remove_file(&tda7802->i2c->dev, &dev_attr_enable);
+}
+
+static const struct snd_soc_component_driver tda7802_component_driver = {
+	.probe = tda7802_probe,
+	.remove = tda7802_remove,
+};
 
 static int tda7802_i2c_probe(struct i2c_client *i2c,
 			     const struct i2c_device_id *id)
-- 
2.11.0