diff mbox series

HID: mcp2221: add ADC support

Message ID 20201120030103.36138-1-matt.ranostay@konsulko.com (mailing list archive)
State Superseded
Delegated to: Jiri Kosina
Headers show
Series HID: mcp2221: add ADC support | expand

Commit Message

Matt Ranostay Nov. 20, 2020, 3:01 a.m. UTC
Add support for the three 10-bit ADC channels registered via
the IIO subsystem.

Cc: linux-input@vger.kernel.org
Cc: linux-iio@vger.kernel.org
CC: Rishi Gupta <gupt21@gmail.com>
Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
---
 drivers/hid/Kconfig       |  1 +
 drivers/hid/hid-mcp2221.c | 65 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 65 insertions(+), 1 deletion(-)

Comments

rishi gupta Nov. 20, 2020, 1:14 p.m. UTC | #1
On Fri, Nov 20, 2020 at 8:31 AM Matt Ranostay
<matt.ranostay@konsulko.com> wrote:
>
> Add support for the three 10-bit ADC channels registered via
> the IIO subsystem.
>
> Cc: linux-input@vger.kernel.org
> Cc: linux-iio@vger.kernel.org
> CC: Rishi Gupta <gupt21@gmail.com>
> Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
> ---
>  drivers/hid/Kconfig       |  1 +
>  drivers/hid/hid-mcp2221.c | 65 ++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 65 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
> index 05315b434276..4795744d9979 100644
> --- a/drivers/hid/Kconfig
> +++ b/drivers/hid/Kconfig
> @@ -1157,6 +1157,7 @@ config HID_MCP2221
>         tristate "Microchip MCP2221 HID USB-to-I2C/SMbus host support"
>         depends on USB_HID && I2C
>         depends on GPIOLIB
> +       depends on IIO
I am wondering what will happen on systems which do not enable IIO.
This driver can not be used there.
Is my understanding correct?
>         help
>         Provides I2C and SMBUS host adapter functionality over USB-HID
>         through MCP2221 device.
> diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
> index 0d27ccb55dd9..7e62f1dc54d3 100644
> --- a/drivers/hid/hid-mcp2221.c
> +++ b/drivers/hid/hid-mcp2221.c
> @@ -18,6 +18,9 @@
>  #include <linux/gpio/driver.h>
>  #include "hid-ids.h"
>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
>  /* Commands codes in a raw output report */
>  enum {
>         MCP2221_I2C_WR_DATA = 0x90,
> @@ -56,6 +59,7 @@ 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 +71,11 @@ struct mcp2221 {
>         struct gpio_chip *gc;
>         u8 gp_idx;
>         u8 gpio_dir;
> +       u16 adc_values[3];
> +};
> +
> +struct mcp2221_iio {
> +       struct mcp2221 *mcp;
>  };
>
>  /*
> @@ -712,6 +721,7 @@ 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;
> @@ -791,11 +801,54 @@ static int mcp2221_raw_event(struct hid_device *hdev,
>         return 1;
>  }
>
> +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_probe(struct hid_device *hdev,
>                                         const struct hid_device_id *id)
>  {
>         int ret;
>         struct mcp2221 *mcp;
> +       struct mcp2221_iio *iio;
>
>         mcp = devm_kzalloc(&hdev->dev, sizeof(*mcp), GFP_KERNEL);
>         if (!mcp)
> @@ -869,8 +922,17 @@ static int mcp2221_probe(struct hid_device *hdev,
>         if (ret)
>                 goto err_gc;
>
> -       return 0;
> +       mcp->indio_dev = devm_iio_device_alloc(&hdev->dev, sizeof(*iio));
> +       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);
>  err_gc:
>         i2c_del_adapter(&mcp->adapter);
>  err_i2c:
> @@ -884,6 +946,7 @@ static void mcp2221_remove(struct hid_device *hdev)
>  {
>         struct mcp2221 *mcp = hid_get_drvdata(hdev);
>
> +       iio_device_unregister(mcp->indio_dev);
>         i2c_del_adapter(&mcp->adapter);
>         hid_hw_close(mcp->hdev);
>         hid_hw_stop(mcp->hdev);
> --
> 2.20.1
>
Matt Ranostay Nov. 20, 2020, 7:17 p.m. UTC | #2
On Fri, Nov 20, 2020 at 5:15 AM rishi gupta <gupt21@gmail.com> wrote:
>
> On Fri, Nov 20, 2020 at 8:31 AM Matt Ranostay
> <matt.ranostay@konsulko.com> wrote:
> >
> > Add support for the three 10-bit ADC channels registered via
> > the IIO subsystem.
> >
> > Cc: linux-input@vger.kernel.org
> > Cc: linux-iio@vger.kernel.org
> > CC: Rishi Gupta <gupt21@gmail.com>
> > Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
> > ---
> >  drivers/hid/Kconfig       |  1 +
> >  drivers/hid/hid-mcp2221.c | 65 ++++++++++++++++++++++++++++++++++++++-
> >  2 files changed, 65 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
> > index 05315b434276..4795744d9979 100644
> > --- a/drivers/hid/Kconfig
> > +++ b/drivers/hid/Kconfig
> > @@ -1157,6 +1157,7 @@ config HID_MCP2221
> >         tristate "Microchip MCP2221 HID USB-to-I2C/SMbus host support"
> >         depends on USB_HID && I2C
> >         depends on GPIOLIB
> > +       depends on IIO
> I am wondering what will happen on systems which do not enable IIO.
> This driver can not be used there.
> Is my understanding correct?

Actually yeah this should be "select IIO" to avoid that issue.

- Matt

> >         help
> >         Provides I2C and SMBUS host adapter functionality over USB-HID
> >         through MCP2221 device.
> > diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
> > index 0d27ccb55dd9..7e62f1dc54d3 100644
> > --- a/drivers/hid/hid-mcp2221.c
> > +++ b/drivers/hid/hid-mcp2221.c
> > @@ -18,6 +18,9 @@
> >  #include <linux/gpio/driver.h>
> >  #include "hid-ids.h"
> >
> > +#include <linux/iio/iio.h>
> > +#include <linux/iio/sysfs.h>
> > +
> >  /* Commands codes in a raw output report */
> >  enum {
> >         MCP2221_I2C_WR_DATA = 0x90,
> > @@ -56,6 +59,7 @@ 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 +71,11 @@ struct mcp2221 {
> >         struct gpio_chip *gc;
> >         u8 gp_idx;
> >         u8 gpio_dir;
> > +       u16 adc_values[3];
> > +};
> > +
> > +struct mcp2221_iio {
> > +       struct mcp2221 *mcp;
> >  };
> >
> >  /*
> > @@ -712,6 +721,7 @@ 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;
> > @@ -791,11 +801,54 @@ static int mcp2221_raw_event(struct hid_device *hdev,
> >         return 1;
> >  }
> >
> > +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_probe(struct hid_device *hdev,
> >                                         const struct hid_device_id *id)
> >  {
> >         int ret;
> >         struct mcp2221 *mcp;
> > +       struct mcp2221_iio *iio;
> >
> >         mcp = devm_kzalloc(&hdev->dev, sizeof(*mcp), GFP_KERNEL);
> >         if (!mcp)
> > @@ -869,8 +922,17 @@ static int mcp2221_probe(struct hid_device *hdev,
> >         if (ret)
> >                 goto err_gc;
> >
> > -       return 0;
> > +       mcp->indio_dev = devm_iio_device_alloc(&hdev->dev, sizeof(*iio));
> > +       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);
> >  err_gc:
> >         i2c_del_adapter(&mcp->adapter);
> >  err_i2c:
> > @@ -884,6 +946,7 @@ static void mcp2221_remove(struct hid_device *hdev)
> >  {
> >         struct mcp2221 *mcp = hid_get_drvdata(hdev);
> >
> > +       iio_device_unregister(mcp->indio_dev);
> >         i2c_del_adapter(&mcp->adapter);
> >         hid_hw_close(mcp->hdev);
> >         hid_hw_stop(mcp->hdev);
> > --
> > 2.20.1
> >
Lars-Peter Clausen Nov. 20, 2020, 7:54 p.m. UTC | #3
On 11/20/20 8:17 PM, Matt Ranostay wrote:
> On Fri, Nov 20, 2020 at 5:15 AM rishi gupta <gupt21@gmail.com> wrote:
>> On Fri, Nov 20, 2020 at 8:31 AM Matt Ranostay
>> <matt.ranostay@konsulko.com> wrote:
>>> Add support for the three 10-bit ADC channels registered via
>>> the IIO subsystem.
>>>
>>> Cc: linux-input@vger.kernel.org
>>> Cc: linux-iio@vger.kernel.org
>>> CC: Rishi Gupta <gupt21@gmail.com>
>>> Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
>>> ---
>>>   drivers/hid/Kconfig       |  1 +
>>>   drivers/hid/hid-mcp2221.c | 65 ++++++++++++++++++++++++++++++++++++++-
>>>   2 files changed, 65 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
>>> index 05315b434276..4795744d9979 100644
>>> --- a/drivers/hid/Kconfig
>>> +++ b/drivers/hid/Kconfig
>>> @@ -1157,6 +1157,7 @@ config HID_MCP2221
>>>          tristate "Microchip MCP2221 HID USB-to-I2C/SMbus host support"
>>>          depends on USB_HID && I2C
>>>          depends on GPIOLIB
>>> +       depends on IIO
>> I am wondering what will happen on systems which do not enable IIO.
>> This driver can not be used there.
>> Is my understanding correct?
> Actually yeah this should be "select IIO" to avoid that issue.

No, we should not have a individual driver select a framework. This will 
cause all kinds of issues with reverse dependencies.

It might be worth splitting this driver into a MFD driver, then the MFD 
cells could have their own module that depend on the subsystem and if 
not enabled the functionality will not be provided.

- Lars
Matt Ranostay Nov. 20, 2020, 8:31 p.m. UTC | #4
On Fri, Nov 20, 2020 at 11:54 AM Lars-Peter Clausen <lars@metafoo.de> wrote:
>
> On 11/20/20 8:17 PM, Matt Ranostay wrote:
> > On Fri, Nov 20, 2020 at 5:15 AM rishi gupta <gupt21@gmail.com> wrote:
> >> On Fri, Nov 20, 2020 at 8:31 AM Matt Ranostay
> >> <matt.ranostay@konsulko.com> wrote:
> >>> Add support for the three 10-bit ADC channels registered via
> >>> the IIO subsystem.
> >>>
> >>> Cc: linux-input@vger.kernel.org
> >>> Cc: linux-iio@vger.kernel.org
> >>> CC: Rishi Gupta <gupt21@gmail.com>
> >>> Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
> >>> ---
> >>>   drivers/hid/Kconfig       |  1 +
> >>>   drivers/hid/hid-mcp2221.c | 65 ++++++++++++++++++++++++++++++++++++++-
> >>>   2 files changed, 65 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
> >>> index 05315b434276..4795744d9979 100644
> >>> --- a/drivers/hid/Kconfig
> >>> +++ b/drivers/hid/Kconfig
> >>> @@ -1157,6 +1157,7 @@ config HID_MCP2221
> >>>          tristate "Microchip MCP2221 HID USB-to-I2C/SMbus host support"
> >>>          depends on USB_HID && I2C
> >>>          depends on GPIOLIB
> >>> +       depends on IIO
> >> I am wondering what will happen on systems which do not enable IIO.
> >> This driver can not be used there.
> >> Is my understanding correct?
> > Actually yeah this should be "select IIO" to avoid that issue.
>
> No, we should not have a individual driver select a framework. This will
> cause all kinds of issues with reverse dependencies.
>
> It might be worth splitting this driver into a MFD driver, then the MFD
> cells could have their own module that depend on the subsystem and if
> not enabled the functionality will not be provided.

Would it make sense to use IS_REACHABLE(CONFIG_IIO) for the iio blocks?

Guessing the weak reference "imply IIO" would still be bad for the
driver selecting a framework?

Thanks,

Matt

>
> - Lars
>
Jonathan Cameron Nov. 21, 2020, 3:10 p.m. UTC | #5
On Fri, 20 Nov 2020 12:31:23 -0800
Matt Ranostay <matt.ranostay@konsulko.com> wrote:

> On Fri, Nov 20, 2020 at 11:54 AM Lars-Peter Clausen <lars@metafoo.de> wrote:
> >
> > On 11/20/20 8:17 PM, Matt Ranostay wrote:  
> > > On Fri, Nov 20, 2020 at 5:15 AM rishi gupta <gupt21@gmail.com> wrote:  
> > >> On Fri, Nov 20, 2020 at 8:31 AM Matt Ranostay
> > >> <matt.ranostay@konsulko.com> wrote:  
> > >>> Add support for the three 10-bit ADC channels registered via
> > >>> the IIO subsystem.
> > >>>
> > >>> Cc: linux-input@vger.kernel.org
> > >>> Cc: linux-iio@vger.kernel.org
> > >>> CC: Rishi Gupta <gupt21@gmail.com>
> > >>> Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
> > >>> ---
> > >>>   drivers/hid/Kconfig       |  1 +
> > >>>   drivers/hid/hid-mcp2221.c | 65 ++++++++++++++++++++++++++++++++++++++-
> > >>>   2 files changed, 65 insertions(+), 1 deletion(-)
> > >>>
> > >>> diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
> > >>> index 05315b434276..4795744d9979 100644
> > >>> --- a/drivers/hid/Kconfig
> > >>> +++ b/drivers/hid/Kconfig
> > >>> @@ -1157,6 +1157,7 @@ config HID_MCP2221
> > >>>          tristate "Microchip MCP2221 HID USB-to-I2C/SMbus host support"
> > >>>          depends on USB_HID && I2C
> > >>>          depends on GPIOLIB
> > >>> +       depends on IIO  
> > >> I am wondering what will happen on systems which do not enable IIO.
> > >> This driver can not be used there.
> > >> Is my understanding correct?  
> > > Actually yeah this should be "select IIO" to avoid that issue.  
> >
> > No, we should not have a individual driver select a framework. This will
> > cause all kinds of issues with reverse dependencies.
> >
> > It might be worth splitting this driver into a MFD driver, then the MFD
> > cells could have their own module that depend on the subsystem and if
> > not enabled the functionality will not be provided.  
> 
> Would it make sense to use IS_REACHABLE(CONFIG_IIO) for the iio blocks?
> 
> Guessing the weak reference "imply IIO" would still be bad for the
> driver selecting a framework?

A lesser option than going full MFD for this (which is probably the
right design decision but is a big change) would be to just put the
IIO stuff in a separate C file and use some build time magic.

I agree with Lars though that this is probably better done as an MFD.
It supports a bunch of things in entirely different subsystems afterall.

Jonathan

> 
> Thanks,
> 
> Matt
> 
> >
> > - Lars
> >
diff mbox series

Patch

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 05315b434276..4795744d9979 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -1157,6 +1157,7 @@  config HID_MCP2221
 	tristate "Microchip MCP2221 HID USB-to-I2C/SMbus host support"
 	depends on USB_HID && I2C
 	depends on GPIOLIB
+	depends on IIO
 	help
 	Provides I2C and SMBUS host adapter functionality over USB-HID
 	through MCP2221 device.
diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
index 0d27ccb55dd9..7e62f1dc54d3 100644
--- a/drivers/hid/hid-mcp2221.c
+++ b/drivers/hid/hid-mcp2221.c
@@ -18,6 +18,9 @@ 
 #include <linux/gpio/driver.h>
 #include "hid-ids.h"
 
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
 /* Commands codes in a raw output report */
 enum {
 	MCP2221_I2C_WR_DATA = 0x90,
@@ -56,6 +59,7 @@  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 +71,11 @@  struct mcp2221 {
 	struct gpio_chip *gc;
 	u8 gp_idx;
 	u8 gpio_dir;
+	u16 adc_values[3];
+};
+
+struct mcp2221_iio {
+	struct mcp2221 *mcp;
 };
 
 /*
@@ -712,6 +721,7 @@  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;
@@ -791,11 +801,54 @@  static int mcp2221_raw_event(struct hid_device *hdev,
 	return 1;
 }
 
+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_probe(struct hid_device *hdev,
 					const struct hid_device_id *id)
 {
 	int ret;
 	struct mcp2221 *mcp;
+	struct mcp2221_iio *iio;
 
 	mcp = devm_kzalloc(&hdev->dev, sizeof(*mcp), GFP_KERNEL);
 	if (!mcp)
@@ -869,8 +922,17 @@  static int mcp2221_probe(struct hid_device *hdev,
 	if (ret)
 		goto err_gc;
 
-	return 0;
+	mcp->indio_dev = devm_iio_device_alloc(&hdev->dev, sizeof(*iio));
+	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);
 err_gc:
 	i2c_del_adapter(&mcp->adapter);
 err_i2c:
@@ -884,6 +946,7 @@  static void mcp2221_remove(struct hid_device *hdev)
 {
 	struct mcp2221 *mcp = hid_get_drvdata(hdev);
 
+	iio_device_unregister(mcp->indio_dev);
 	i2c_del_adapter(&mcp->adapter);
 	hid_hw_close(mcp->hdev);
 	hid_hw_stop(mcp->hdev);