diff mbox series

[v8,2/3] Input: adc-joystick - Add polled input device support

Message ID 20220721164603.13534-3-macroalpha82@gmail.com (mailing list archive)
State Changes Requested
Headers show
Series dt-bindings: adc-joystick: add poll-interval | expand

Commit Message

Chris Morgan July 21, 2022, 4:46 p.m. UTC
From: Chris Morgan <macromorgan@hotmail.com>

Add polled input device support to the adc-joystick driver. This is
useful for devices which do not have hardware capable triggers on
their SARADC. Code modified from adc-joystick.c changes made by Maya
Matuszczyk.

Signed-off-by: Maya Matuszczyk <maccraft123mc@gmail.com>
Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
---
 drivers/input/joystick/adc-joystick.c | 82 ++++++++++++++++++++-------
 1 file changed, 62 insertions(+), 20 deletions(-)

Comments

Artur Rojek July 28, 2022, 8:26 p.m. UTC | #1
On 2022-07-21 18:46, Chris Morgan wrote:
> From: Chris Morgan <macromorgan@hotmail.com>
> 
> Add polled input device support to the adc-joystick driver. This is
> useful for devices which do not have hardware capable triggers on
> their SARADC. Code modified from adc-joystick.c changes made by Maya
> Matuszczyk.
> 
> Signed-off-by: Maya Matuszczyk <maccraft123mc@gmail.com>
> Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
> ---
Hey Chris,

sorry for the late response. Comments in-line.

Cheers,
Artur
>  drivers/input/joystick/adc-joystick.c | 82 ++++++++++++++++++++-------
>  1 file changed, 62 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/input/joystick/adc-joystick.c
> b/drivers/input/joystick/adc-joystick.c
> index 78ebca7d400a..085b8e10dfb5 100644
> --- a/drivers/input/joystick/adc-joystick.c
> +++ b/drivers/input/joystick/adc-joystick.c
> @@ -26,8 +26,23 @@ struct adc_joystick {
>  	struct adc_joystick_axis *axes;
>  	struct iio_channel *chans;
>  	int num_chans;
> +	bool polled;
>  };
> 
> +static void adc_joystick_poll(struct input_dev *input)
> +{
> +	struct adc_joystick *joy = input_get_drvdata(input);
> +	int i, val, ret;
> +
> +	for (i = 0; i < joy->num_chans; i++) {
> +		ret = iio_read_channel_raw(&joy->chans[i], &val);
> +		if (ret < 0)
> +			return;
> +		input_report_abs(input, joy->axes[i].code, val);
> +	}
> +	input_sync(input);
> +}
> +
>  static int adc_joystick_handle(const void *data, void *private)
>  {
>  	struct adc_joystick *joy = private;
> @@ -178,7 +193,9 @@ static int adc_joystick_probe(struct 
> platform_device *pdev)
>  	struct input_dev *input;
>  	int error;
>  	int bits;
> +	int chan_storage;
>  	int i;
> +	unsigned int poll_interval;
> 
>  	joy = devm_kzalloc(dev, sizeof(*joy), GFP_KERNEL);
>  	if (!joy)
> @@ -192,16 +209,31 @@ static int adc_joystick_probe(struct
> platform_device *pdev)
>  		return error;
>  	}
> 
> -	/* Count how many channels we got. NULL terminated. */
> +	if (device_property_present(dev, "poll-interval")) {
> +		error = device_property_read_u32(dev, "poll-interval",
> +						 &poll_interval);
> +		if (error)
> +			return error;
> +		joy->polled = true;
> +	}
> +
> +	/* Count how many channels we got. NULL terminated. Do not check the
> +	 * storage size if using polling.
> +	 */
As per Linux coding style, the multi-line comment opens with a lone `/*`
line. Also, move the second sentence into a new line for readability.

> +	chan_storage = joy->chans[0].channel->scan_type.storagebits;
>  	for (i = 0; joy->chans[i].indio_dev; i++) {
> -		bits = joy->chans[i].channel->scan_type.storagebits;
> -		if (!bits || bits > 16) {
> -			dev_err(dev, "Unsupported channel storage size\n");
> -			return -EINVAL;
> -		}
> -		if (bits != joy->chans[0].channel->scan_type.storagebits) {
> -			dev_err(dev, "Channels must have equal storage size\n");
> -			return -EINVAL;
> +		if (!joy->polled) {
> +			bits = joy->chans[i].channel->scan_type.storagebits;
> +			if (!bits || bits > 16) {
> +				dev_err(dev,
> +					"Unsupported channel storage size\n");
> +				return -EINVAL;
> +			}
> +			if (bits != chan_storage) {
> +				dev_err(dev,
> +					"Channels must be equal size\n");
> +				return -EINVAL;
> +			}
Just do `for (i = 0; !joy->polled && joy->chans[i].indio_dev; i++)`, as
this will terminate early if we're polling.
Then we'll also be able to restore the loop body to its original code 
and
get rid of that `chan_storage` helper.

>  		}
>  	}
>  	joy->num_chans = i;
> @@ -215,8 +247,14 @@ static int adc_joystick_probe(struct 
> platform_device *pdev)
>  	joy->input = input;
>  	input->name = pdev->name;
>  	input->id.bustype = BUS_HOST;
> -	input->open = adc_joystick_open;
> -	input->close = adc_joystick_close;
> +
> +	if (joy->polled) {
> +		input_setup_polling(input, adc_joystick_poll);
> +		input_set_poll_interval(input, poll_interval);
> +	} else {
> +		input->open = adc_joystick_open;
> +		input->close = adc_joystick_close;
> +	}
> 
>  	error = adc_joystick_set_axes(dev, joy);
>  	if (error)
> @@ -229,16 +267,20 @@ static int adc_joystick_probe(struct
> platform_device *pdev)
>  		return error;
>  	}
> 
> -	joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle, joy);
> -	if (IS_ERR(joy->buffer)) {
> -		dev_err(dev, "Unable to allocate callback buffer\n");
> -		return PTR_ERR(joy->buffer);
> -	}
> +	if (!joy->polled) {
> +		joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle,
> +						     joy);
> +		if (IS_ERR(joy->buffer)) {
> +			dev_err(dev, "Unable to allocate callback buffer\n");
> +			return PTR_ERR(joy->buffer);
> +		}
> 
> -	error = devm_add_action_or_reset(dev, adc_joystick_cleanup, 
> joy->buffer);
> -	if (error)  {
> -		dev_err(dev, "Unable to add action\n");
> -		return error;
> +		error = devm_add_action_or_reset(dev, adc_joystick_cleanup,
> +						 joy->buffer);
> +		if (error)  {
> +			dev_err(dev, "Unable to add action\n");
> +			return error;
> +		}
>  	}
> 
>  	return 0;
Chris Morgan July 29, 2022, 4:30 p.m. UTC | #2
On Thu, Jul 28, 2022 at 10:26:07PM +0200, Artur Rojek wrote:
> On 2022-07-21 18:46, Chris Morgan wrote:
> > From: Chris Morgan <macromorgan@hotmail.com>
> > 
> > Add polled input device support to the adc-joystick driver. This is
> > useful for devices which do not have hardware capable triggers on
> > their SARADC. Code modified from adc-joystick.c changes made by Maya
> > Matuszczyk.
> > 
> > Signed-off-by: Maya Matuszczyk <maccraft123mc@gmail.com>
> > Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
> > ---
> Hey Chris,
> 
> sorry for the late response. Comments in-line.
> 
> Cheers,
> Artur
> >  drivers/input/joystick/adc-joystick.c | 82 ++++++++++++++++++++-------
> >  1 file changed, 62 insertions(+), 20 deletions(-)
> > 
> > diff --git a/drivers/input/joystick/adc-joystick.c
> > b/drivers/input/joystick/adc-joystick.c
> > index 78ebca7d400a..085b8e10dfb5 100644
> > --- a/drivers/input/joystick/adc-joystick.c
> > +++ b/drivers/input/joystick/adc-joystick.c
> > @@ -26,8 +26,23 @@ struct adc_joystick {
> >  	struct adc_joystick_axis *axes;
> >  	struct iio_channel *chans;
> >  	int num_chans;
> > +	bool polled;
> >  };
> > 
> > +static void adc_joystick_poll(struct input_dev *input)
> > +{
> > +	struct adc_joystick *joy = input_get_drvdata(input);
> > +	int i, val, ret;
> > +
> > +	for (i = 0; i < joy->num_chans; i++) {
> > +		ret = iio_read_channel_raw(&joy->chans[i], &val);
> > +		if (ret < 0)
> > +			return;
> > +		input_report_abs(input, joy->axes[i].code, val);
> > +	}
> > +	input_sync(input);
> > +}
> > +
> >  static int adc_joystick_handle(const void *data, void *private)
> >  {
> >  	struct adc_joystick *joy = private;
> > @@ -178,7 +193,9 @@ static int adc_joystick_probe(struct platform_device
> > *pdev)
> >  	struct input_dev *input;
> >  	int error;
> >  	int bits;
> > +	int chan_storage;
> >  	int i;
> > +	unsigned int poll_interval;
> > 
> >  	joy = devm_kzalloc(dev, sizeof(*joy), GFP_KERNEL);
> >  	if (!joy)
> > @@ -192,16 +209,31 @@ static int adc_joystick_probe(struct
> > platform_device *pdev)
> >  		return error;
> >  	}
> > 
> > -	/* Count how many channels we got. NULL terminated. */
> > +	if (device_property_present(dev, "poll-interval")) {
> > +		error = device_property_read_u32(dev, "poll-interval",
> > +						 &poll_interval);
> > +		if (error)
> > +			return error;
> > +		joy->polled = true;
> > +	}
> > +
> > +	/* Count how many channels we got. NULL terminated. Do not check the
> > +	 * storage size if using polling.
> > +	 */
> As per Linux coding style, the multi-line comment opens with a lone `/*`
> line. Also, move the second sentence into a new line for readability.

Gotcha, I always thought it could start this way but had to end with an
empty line. I guess I learned something new.

> 
> > +	chan_storage = joy->chans[0].channel->scan_type.storagebits;
> >  	for (i = 0; joy->chans[i].indio_dev; i++) {
> > -		bits = joy->chans[i].channel->scan_type.storagebits;
> > -		if (!bits || bits > 16) {
> > -			dev_err(dev, "Unsupported channel storage size\n");
> > -			return -EINVAL;
> > -		}
> > -		if (bits != joy->chans[0].channel->scan_type.storagebits) {
> > -			dev_err(dev, "Channels must have equal storage size\n");
> > -			return -EINVAL;
> > +		if (!joy->polled) {
> > +			bits = joy->chans[i].channel->scan_type.storagebits;
> > +			if (!bits || bits > 16) {
> > +				dev_err(dev,
> > +					"Unsupported channel storage size\n");
> > +				return -EINVAL;
> > +			}
> > +			if (bits != chan_storage) {
> > +				dev_err(dev,
> > +					"Channels must be equal size\n");
> > +				return -EINVAL;
> > +			}
> Just do `for (i = 0; !joy->polled && joy->chans[i].indio_dev; i++)`, as
> this will terminate early if we're polling.
> Then we'll also be able to restore the loop body to its original code and
> get rid of that `chan_storage` helper.
> 

Thank you, I was struggling to figure out how to get the code to do
what I wanted while keeping it below 80 columns, this is perfect.

> >  		}
> >  	}
> >  	joy->num_chans = i;
> > @@ -215,8 +247,14 @@ static int adc_joystick_probe(struct
> > platform_device *pdev)
> >  	joy->input = input;
> >  	input->name = pdev->name;
> >  	input->id.bustype = BUS_HOST;
> > -	input->open = adc_joystick_open;
> > -	input->close = adc_joystick_close;
> > +
> > +	if (joy->polled) {
> > +		input_setup_polling(input, adc_joystick_poll);
> > +		input_set_poll_interval(input, poll_interval);
> > +	} else {
> > +		input->open = adc_joystick_open;
> > +		input->close = adc_joystick_close;
> > +	}
> > 
> >  	error = adc_joystick_set_axes(dev, joy);
> >  	if (error)
> > @@ -229,16 +267,20 @@ static int adc_joystick_probe(struct
> > platform_device *pdev)
> >  		return error;
> >  	}
> > 
> > -	joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle, joy);
> > -	if (IS_ERR(joy->buffer)) {
> > -		dev_err(dev, "Unable to allocate callback buffer\n");
> > -		return PTR_ERR(joy->buffer);
> > -	}
> > +	if (!joy->polled) {
> > +		joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle,
> > +						     joy);
> > +		if (IS_ERR(joy->buffer)) {
> > +			dev_err(dev, "Unable to allocate callback buffer\n");
> > +			return PTR_ERR(joy->buffer);
> > +		}
> > 
> > -	error = devm_add_action_or_reset(dev, adc_joystick_cleanup,
> > joy->buffer);
> > -	if (error)  {
> > -		dev_err(dev, "Unable to add action\n");
> > -		return error;
> > +		error = devm_add_action_or_reset(dev, adc_joystick_cleanup,
> > +						 joy->buffer);
> > +		if (error)  {
> > +			dev_err(dev, "Unable to add action\n");
> > +			return error;
> > +		}
> >  	}
> > 
> >  	return 0;
>
Chris Morgan Aug. 3, 2022, 4:53 p.m. UTC | #3
On Fri, Jul 29, 2022 at 11:30:51AM -0500, Chris Morgan wrote:
> On Thu, Jul 28, 2022 at 10:26:07PM +0200, Artur Rojek wrote:
> > On 2022-07-21 18:46, Chris Morgan wrote:
> > > From: Chris Morgan <macromorgan@hotmail.com>
> > > 
> > > Add polled input device support to the adc-joystick driver. This is
> > > useful for devices which do not have hardware capable triggers on
> > > their SARADC. Code modified from adc-joystick.c changes made by Maya
> > > Matuszczyk.
> > > 
> > > Signed-off-by: Maya Matuszczyk <maccraft123mc@gmail.com>
> > > Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
> > > ---
> > Hey Chris,
> > 
> > sorry for the late response. Comments in-line.
> > 
> > Cheers,
> > Artur
> > >  drivers/input/joystick/adc-joystick.c | 82 ++++++++++++++++++++-------
> > >  1 file changed, 62 insertions(+), 20 deletions(-)
> > > 
> > > diff --git a/drivers/input/joystick/adc-joystick.c
> > > b/drivers/input/joystick/adc-joystick.c
> > > index 78ebca7d400a..085b8e10dfb5 100644
> > > --- a/drivers/input/joystick/adc-joystick.c
> > > +++ b/drivers/input/joystick/adc-joystick.c
> > > @@ -26,8 +26,23 @@ struct adc_joystick {
> > >  	struct adc_joystick_axis *axes;
> > >  	struct iio_channel *chans;
> > >  	int num_chans;
> > > +	bool polled;
> > >  };
> > > 
> > > +static void adc_joystick_poll(struct input_dev *input)
> > > +{
> > > +	struct adc_joystick *joy = input_get_drvdata(input);
> > > +	int i, val, ret;
> > > +
> > > +	for (i = 0; i < joy->num_chans; i++) {
> > > +		ret = iio_read_channel_raw(&joy->chans[i], &val);
> > > +		if (ret < 0)
> > > +			return;
> > > +		input_report_abs(input, joy->axes[i].code, val);
> > > +	}
> > > +	input_sync(input);
> > > +}
> > > +
> > >  static int adc_joystick_handle(const void *data, void *private)
> > >  {
> > >  	struct adc_joystick *joy = private;
> > > @@ -178,7 +193,9 @@ static int adc_joystick_probe(struct platform_device
> > > *pdev)
> > >  	struct input_dev *input;
> > >  	int error;
> > >  	int bits;
> > > +	int chan_storage;
> > >  	int i;
> > > +	unsigned int poll_interval;
> > > 
> > >  	joy = devm_kzalloc(dev, sizeof(*joy), GFP_KERNEL);
> > >  	if (!joy)
> > > @@ -192,16 +209,31 @@ static int adc_joystick_probe(struct
> > > platform_device *pdev)
> > >  		return error;
> > >  	}
> > > 
> > > -	/* Count how many channels we got. NULL terminated. */
> > > +	if (device_property_present(dev, "poll-interval")) {
> > > +		error = device_property_read_u32(dev, "poll-interval",
> > > +						 &poll_interval);
> > > +		if (error)
> > > +			return error;
> > > +		joy->polled = true;
> > > +	}
> > > +
> > > +	/* Count how many channels we got. NULL terminated. Do not check the
> > > +	 * storage size if using polling.
> > > +	 */
> > As per Linux coding style, the multi-line comment opens with a lone `/*`
> > line. Also, move the second sentence into a new line for readability.
> 
> Gotcha, I always thought it could start this way but had to end with an
> empty line. I guess I learned something new.
> 
> > 
> > > +	chan_storage = joy->chans[0].channel->scan_type.storagebits;
> > >  	for (i = 0; joy->chans[i].indio_dev; i++) {
> > > -		bits = joy->chans[i].channel->scan_type.storagebits;
> > > -		if (!bits || bits > 16) {
> > > -			dev_err(dev, "Unsupported channel storage size\n");
> > > -			return -EINVAL;
> > > -		}
> > > -		if (bits != joy->chans[0].channel->scan_type.storagebits) {
> > > -			dev_err(dev, "Channels must have equal storage size\n");
> > > -			return -EINVAL;
> > > +		if (!joy->polled) {
> > > +			bits = joy->chans[i].channel->scan_type.storagebits;
> > > +			if (!bits || bits > 16) {
> > > +				dev_err(dev,
> > > +					"Unsupported channel storage size\n");
> > > +				return -EINVAL;
> > > +			}
> > > +			if (bits != chan_storage) {
> > > +				dev_err(dev,
> > > +					"Channels must be equal size\n");
> > > +				return -EINVAL;
> > > +			}
> > Just do `for (i = 0; !joy->polled && joy->chans[i].indio_dev; i++)`, as
> > this will terminate early if we're polling.
> > Then we'll also be able to restore the loop body to its original code and
> > get rid of that `chan_storage` helper.
> > 
> 
> Thank you, I was struggling to figure out how to get the code to do
> what I wanted while keeping it below 80 columns, this is perfect.

The suggested code doesn't work (because it doesn't count the channels, however
it gave me an idea to include a check in each of the if conditions below it to
look for joy->polled, and I think that works. I'll send v9 shortly. Thank you
for all your help.

> 
> > >  		}
> > >  	}
> > >  	joy->num_chans = i;
> > > @@ -215,8 +247,14 @@ static int adc_joystick_probe(struct
> > > platform_device *pdev)
> > >  	joy->input = input;
> > >  	input->name = pdev->name;
> > >  	input->id.bustype = BUS_HOST;
> > > -	input->open = adc_joystick_open;
> > > -	input->close = adc_joystick_close;
> > > +
> > > +	if (joy->polled) {
> > > +		input_setup_polling(input, adc_joystick_poll);
> > > +		input_set_poll_interval(input, poll_interval);
> > > +	} else {
> > > +		input->open = adc_joystick_open;
> > > +		input->close = adc_joystick_close;
> > > +	}
> > > 
> > >  	error = adc_joystick_set_axes(dev, joy);
> > >  	if (error)
> > > @@ -229,16 +267,20 @@ static int adc_joystick_probe(struct
> > > platform_device *pdev)
> > >  		return error;
> > >  	}
> > > 
> > > -	joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle, joy);
> > > -	if (IS_ERR(joy->buffer)) {
> > > -		dev_err(dev, "Unable to allocate callback buffer\n");
> > > -		return PTR_ERR(joy->buffer);
> > > -	}
> > > +	if (!joy->polled) {
> > > +		joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle,
> > > +						     joy);
> > > +		if (IS_ERR(joy->buffer)) {
> > > +			dev_err(dev, "Unable to allocate callback buffer\n");
> > > +			return PTR_ERR(joy->buffer);
> > > +		}
> > > 
> > > -	error = devm_add_action_or_reset(dev, adc_joystick_cleanup,
> > > joy->buffer);
> > > -	if (error)  {
> > > -		dev_err(dev, "Unable to add action\n");
> > > -		return error;
> > > +		error = devm_add_action_or_reset(dev, adc_joystick_cleanup,
> > > +						 joy->buffer);
> > > +		if (error)  {
> > > +			dev_err(dev, "Unable to add action\n");
> > > +			return error;
> > > +		}
> > >  	}
> > > 
> > >  	return 0;
> >
diff mbox series

Patch

diff --git a/drivers/input/joystick/adc-joystick.c b/drivers/input/joystick/adc-joystick.c
index 78ebca7d400a..085b8e10dfb5 100644
--- a/drivers/input/joystick/adc-joystick.c
+++ b/drivers/input/joystick/adc-joystick.c
@@ -26,8 +26,23 @@  struct adc_joystick {
 	struct adc_joystick_axis *axes;
 	struct iio_channel *chans;
 	int num_chans;
+	bool polled;
 };
 
+static void adc_joystick_poll(struct input_dev *input)
+{
+	struct adc_joystick *joy = input_get_drvdata(input);
+	int i, val, ret;
+
+	for (i = 0; i < joy->num_chans; i++) {
+		ret = iio_read_channel_raw(&joy->chans[i], &val);
+		if (ret < 0)
+			return;
+		input_report_abs(input, joy->axes[i].code, val);
+	}
+	input_sync(input);
+}
+
 static int adc_joystick_handle(const void *data, void *private)
 {
 	struct adc_joystick *joy = private;
@@ -178,7 +193,9 @@  static int adc_joystick_probe(struct platform_device *pdev)
 	struct input_dev *input;
 	int error;
 	int bits;
+	int chan_storage;
 	int i;
+	unsigned int poll_interval;
 
 	joy = devm_kzalloc(dev, sizeof(*joy), GFP_KERNEL);
 	if (!joy)
@@ -192,16 +209,31 @@  static int adc_joystick_probe(struct platform_device *pdev)
 		return error;
 	}
 
-	/* Count how many channels we got. NULL terminated. */
+	if (device_property_present(dev, "poll-interval")) {
+		error = device_property_read_u32(dev, "poll-interval",
+						 &poll_interval);
+		if (error)
+			return error;
+		joy->polled = true;
+	}
+
+	/* Count how many channels we got. NULL terminated. Do not check the
+	 * storage size if using polling.
+	 */
+	chan_storage = joy->chans[0].channel->scan_type.storagebits;
 	for (i = 0; joy->chans[i].indio_dev; i++) {
-		bits = joy->chans[i].channel->scan_type.storagebits;
-		if (!bits || bits > 16) {
-			dev_err(dev, "Unsupported channel storage size\n");
-			return -EINVAL;
-		}
-		if (bits != joy->chans[0].channel->scan_type.storagebits) {
-			dev_err(dev, "Channels must have equal storage size\n");
-			return -EINVAL;
+		if (!joy->polled) {
+			bits = joy->chans[i].channel->scan_type.storagebits;
+			if (!bits || bits > 16) {
+				dev_err(dev,
+					"Unsupported channel storage size\n");
+				return -EINVAL;
+			}
+			if (bits != chan_storage) {
+				dev_err(dev,
+					"Channels must be equal size\n");
+				return -EINVAL;
+			}
 		}
 	}
 	joy->num_chans = i;
@@ -215,8 +247,14 @@  static int adc_joystick_probe(struct platform_device *pdev)
 	joy->input = input;
 	input->name = pdev->name;
 	input->id.bustype = BUS_HOST;
-	input->open = adc_joystick_open;
-	input->close = adc_joystick_close;
+
+	if (joy->polled) {
+		input_setup_polling(input, adc_joystick_poll);
+		input_set_poll_interval(input, poll_interval);
+	} else {
+		input->open = adc_joystick_open;
+		input->close = adc_joystick_close;
+	}
 
 	error = adc_joystick_set_axes(dev, joy);
 	if (error)
@@ -229,16 +267,20 @@  static int adc_joystick_probe(struct platform_device *pdev)
 		return error;
 	}
 
-	joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle, joy);
-	if (IS_ERR(joy->buffer)) {
-		dev_err(dev, "Unable to allocate callback buffer\n");
-		return PTR_ERR(joy->buffer);
-	}
+	if (!joy->polled) {
+		joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle,
+						     joy);
+		if (IS_ERR(joy->buffer)) {
+			dev_err(dev, "Unable to allocate callback buffer\n");
+			return PTR_ERR(joy->buffer);
+		}
 
-	error = devm_add_action_or_reset(dev, adc_joystick_cleanup, joy->buffer);
-	if (error)  {
-		dev_err(dev, "Unable to add action\n");
-		return error;
+		error = devm_add_action_or_reset(dev, adc_joystick_cleanup,
+						 joy->buffer);
+		if (error)  {
+			dev_err(dev, "Unable to add action\n");
+			return error;
+		}
 	}
 
 	return 0;