[PATCH v2] HID: mcp2221: add ADC support

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Add support for the three 10-bit ADC channels registered via
the IIO subsystem.

Cc: linux-input@xxxxxxxxxxxxxxx
Cc: linux-iio@xxxxxxxxxxxxxxx
CC: Rishi Gupta <gupt21@xxxxxxxxx>
Signed-off-by: Matt Ranostay <matt.ranostay@xxxxxxxxxxxx>
---

Changes from v1:

* Removed 'select IIO' from Kconfig
* Removed useless iio/sysfs.h include
* Add IS_REACHABLE checks for IIO subsystem 

 drivers/hid/hid-mcp2221.c | 89 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
index 0d27ccb55dd9..36fa9336c4c5 100644
--- a/drivers/hid/hid-mcp2221.c
+++ b/drivers/hid/hid-mcp2221.c
@@ -16,6 +16,7 @@
 #include <linux/hidraw.h>
 #include <linux/i2c.h>
 #include <linux/gpio/driver.h>
+#include <linux/iio/iio.h>
 #include "hid-ids.h"
 
 /* Commands codes in a raw output report */
@@ -56,6 +57,7 @@ enum {
  */
 struct mcp2221 {
 	struct hid_device *hdev;
+	struct iio_dev *indio_dev;
 	struct i2c_adapter adapter;
 	struct mutex lock;
 	struct completion wait_in_report;
@@ -67,6 +69,11 @@ struct mcp2221 {
 	struct gpio_chip *gc;
 	u8 gp_idx;
 	u8 gpio_dir;
+	u16 adc_values[3];
+};
+
+struct mcp2221_iio {
+	struct mcp2221 *mcp;
 };
 
 /*
@@ -712,6 +719,7 @@ static int mcp2221_raw_event(struct hid_device *hdev,
 				break;
 			}
 			mcp->status = mcp_get_i2c_eng_state(mcp, data, 8);
+			memcpy(&mcp->adc_values, &data[50], 6);
 			break;
 		default:
 			mcp->status = -EIO;
@@ -791,6 +799,79 @@ static int mcp2221_raw_event(struct hid_device *hdev,
 	return 1;
 }
 
+#if IS_REACHABLE(CONFIG_IIO)
+
+static int mcp2221_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *channel, int *val,
+			    int *val2, long mask)
+{
+
+	struct mcp2221_iio *priv = iio_priv(indio_dev);
+	struct mcp2221 *mcp = priv->mcp;
+	int ret;
+
+	mutex_lock(&mcp->lock);
+
+	/* Read ADC values */
+	ret = mcp_chk_last_cmd_status(mcp);
+	if (ret < 0)
+		return ret;
+
+	*val = le16_to_cpu(mcp->adc_values[channel->channel]);
+
+	mutex_unlock(&mcp->lock);
+
+	return IIO_VAL_INT;
+}
+
+static const struct iio_info mcp2221_info = {
+	.read_raw = &mcp2221_read_raw,
+};
+
+#define MCP2221_ADC_CHANNEL(idx) \
+	{ \
+		.type = IIO_VOLTAGE, \
+		.indexed = 1, \
+		.channel = idx, \
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+		.scan_index = -1, \
+	}
+
+static const struct iio_chan_spec mcp2221_channels[] = {
+	MCP2221_ADC_CHANNEL(0),
+	MCP2221_ADC_CHANNEL(1),
+	MCP2221_ADC_CHANNEL(2),
+};
+
+static int mcp2221_register_adcs(struct device *dev, struct mcp2221 *mcp)
+{
+	struct mcp2221_iio *iio;
+
+	mcp->indio_dev = devm_iio_device_alloc(dev, sizeof(*iio));
+	if (!mcp->indio_dev)
+		return -ENOMEM;
+
+	iio = iio_priv(mcp->indio_dev);
+	iio->mcp = mcp;
+
+	mcp->indio_dev->name = "mcp2221_adc";
+	mcp->indio_dev->modes = INDIO_DIRECT_MODE;
+	mcp->indio_dev->info = &mcp2221_info;
+	mcp->indio_dev->channels = mcp2221_channels;
+	mcp->indio_dev->num_channels = ARRAY_SIZE(mcp2221_channels);
+
+	return iio_device_register(mcp->indio_dev);
+}
+
+#else
+
+static int mcp2221_register_adcs(struct device *dev, struct mcp2221 *mcp)
+{
+	return 0;
+}
+
+#endif
+
 static int mcp2221_probe(struct hid_device *hdev,
 					const struct hid_device_id *id)
 {
@@ -869,6 +950,10 @@ static int mcp2221_probe(struct hid_device *hdev,
 	if (ret)
 		goto err_gc;
 
+	ret = mcp2221_register_adcs(&hdev->dev, mcp);
+	if (ret)
+		goto err_gc;
+
 	return 0;
 
 err_gc:
@@ -884,6 +969,10 @@ static void mcp2221_remove(struct hid_device *hdev)
 {
 	struct mcp2221 *mcp = hid_get_drvdata(hdev);
 
+#if IS_REACHABLE(CONFIG_IIO)
+	iio_device_unregister(mcp->indio_dev);
+#endif
+
 	i2c_del_adapter(&mcp->adapter);
 	hid_hw_close(mcp->hdev);
 	hid_hw_stop(mcp->hdev);
-- 
2.20.1




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