Re: [PATCH v4] media: video-i2c: add hwmon support for amg88xx

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Jun 28, 2018 at 11:11:04AM -0700, Matt Ranostay wrote:
> 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@vger.kernel.org
> Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>

Acked-by: Guenter Roeck <linux@roeck-us.net>

> ---
>  drivers/media/i2c/Kconfig     |  1 +
>  drivers/media/i2c/video-i2c.c | 81 +++++++++++++++++++++++++++++++++++
>  2 files changed, 82 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 
> 
> Changes from v3:
> * add 'imply HWMON' to avoid build race conditions
> 
> diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
> index 341452fe98df..799a0278b690 100644
> --- a/drivers/media/i2c/Kconfig
> +++ b/drivers/media/i2c/Kconfig
> @@ -1002,6 +1002,7 @@ config VIDEO_I2C
>  	tristate "I2C transport video support"
>  	depends on VIDEO_V4L2 && I2C
>  	select VIDEOBUF2_VMALLOC
> +	imply HWMON
>  	---help---
>  	  Enable the I2C transport video support which supports the
>  	  following:
> 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
> 
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