AMG88xx has an on-board thermistor which is used for more accurate
processing of its temperature readings from the 8x8 thermopile array
Cc: linux-hwmon@xxxxxxxxxxxxxxx
Signed-off-by: Matt Ranostay <matt.ranostay@xxxxxxxxxxxx>
---
drivers/media/i2c/video-i2c.c | 81 +++++++++++++++++++++++++++++++++++
1 file changed, 81 insertions(+)
Changes from v1:
* remove unneeded include statement
* removed evil &NULL dereference if hwmon isn't enabled
* return PTR_ERR instead of boolean IS_ERR from amg88xx_hwmon_init()
* use error code returned from hwmon_init() to display dev_warn
Changes from v2:
* change #ifdef check to use cleaner IS_ENABLED(CONFIG_HWMON)
* document why the temperature value isn't sign extended more concisely
diff --git a/drivers/media/i2c/video-i2c.c b/drivers/media/i2c/video-i2c.c
index 0b347cc19aa5..7dc9338502e5 100644
--- a/drivers/media/i2c/video-i2c.c
+++ b/drivers/media/i2c/video-i2c.c
@@ -10,6 +10,7 @@
#include <linux/delay.h>
#include <linux/freezer.h>
+#include <linux/hwmon.h>
#include <linux/kthread.h>
#include <linux/i2c.h>
#include <linux/list.h>
@@ -77,6 +78,9 @@ struct video_i2c_chip {
/* xfer function */
int (*xfer)(struct video_i2c_data *data, char *buf);
+
+ /* hwmon init function */
+ int (*hwmon_init)(struct video_i2c_data *data);
};
static int amg88xx_xfer(struct video_i2c_data *data, char *buf)
@@ -101,6 +105,74 @@ static int amg88xx_xfer(struct video_i2c_data *data, char *buf)
return (ret == 2) ? 0 : -EIO;
}
+#if IS_ENABLED(CONFIG_HWMON)
+
+static const u32 amg88xx_temp_config[] = {
+ HWMON_T_INPUT,
+ 0
+};
+
+static const struct hwmon_channel_info amg88xx_temp = {
+ .type = hwmon_temp,
+ .config = amg88xx_temp_config,
+};
+
+static const struct hwmon_channel_info *amg88xx_info[] = {
+ &amg88xx_temp,
+ NULL
+};
+
+static umode_t amg88xx_is_visible(const void *drvdata,
+ enum hwmon_sensor_types type,
+ u32 attr, int channel)
+{
+ return 0444;
+}
+
+static int amg88xx_read(struct device *dev, enum hwmon_sensor_types type,
+ u32 attr, int channel, long *val)
+{
+ struct video_i2c_data *data = dev_get_drvdata(dev);
+ struct i2c_client *client = data->client;
+ int tmp = i2c_smbus_read_word_data(client, 0x0e);
+
+ if (tmp < 0)
+ return tmp;
+
+ /*
+ * Check for sign bit, this isn't a two's complement value but an
+ * absolute temperature that needs to be inverted in the case of being
+ * negative.
+ */
+ if (tmp & BIT(11))
+ tmp = -(tmp & 0x7ff);
+
+ *val = (tmp * 625) / 10;
+
+ return 0;
+}
+
+static const struct hwmon_ops amg88xx_hwmon_ops = {
+ .is_visible = amg88xx_is_visible,
+ .read = amg88xx_read,
+};
+
+static const struct hwmon_chip_info amg88xx_chip_info = {
+ .ops = &amg88xx_hwmon_ops,
+ .info = amg88xx_info,
+};
+
+static int amg88xx_hwmon_init(struct video_i2c_data *data)
+{
+ void *hwmon = devm_hwmon_device_register_with_info(&data->client->dev,
+ "amg88xx", data, &amg88xx_chip_info, NULL);
+
+ return PTR_ERR(hwmon);
+}
+#else
+#define amg88xx_hwmon_init NULL
+#endif
+
#define AMG88XX 0
static const struct video_i2c_chip video_i2c_chip[] = {
@@ -111,6 +183,7 @@ static const struct video_i2c_chip video_i2c_chip[] = {
.buffer_size = 128,
.bpp = 16,
.xfer = &amg88xx_xfer,
+ .hwmon_init = amg88xx_hwmon_init,
},
};
@@ -505,6 +578,14 @@ static int video_i2c_probe(struct i2c_client *client,
video_set_drvdata(&data->vdev, data);
i2c_set_clientdata(client, data);
+ if (data->chip->hwmon_init) {
+ ret = data->chip->hwmon_init(data);
+ if (ret < 0) {
+ dev_warn(&client->dev,
+ "failed to register hwmon device\n");
+ }
+ }
+
ret = video_register_device(&data->vdev, VFL_TYPE_GRABBER, -1);
if (ret < 0)
goto error_unregister_device;
--
2.17.1
