[PATCH v8 0/3] dt-bindings: adc-joystick: add poll-interval

[PATCH v8 0/3] dt-bindings: adc-joystick: add poll-interval

[Chris Morgan]

From: Chris Morgan <macromorgan@hotmail.com>

Add support to the existing adc-joystick driver to support polling
rather than relying on triggered buffers. This is useful for devices
that do not offer triggered buffers in hardware. Code adapted from
changes made by Maya Matuszczyk <maccraft123mc@gmail.com>.

Changes from V7:
 - Dropped acks from adc-joystick.c changes, as it has been altered
   somewhat since v7.
 - Improved checking value of poll-interval to ensure explicit error
   handling in the event of malformed values.
 - Adjusted logic to not check for storagebits if polling is in use,
   which allows adc-joystick to work in polling mode for devices that
   utilize a mux (such as the Odroid Go Super and the Anbernic RG353).
 - Changed error message and channel size comparison logic slightly to
   ensure code can fit within 80 character column width.

Changes from V6:
 - Reverted back to "poll-interval" after mailing list discussion.
 - Referenced input.yaml for definition of poll-interval in adc-joystick
   documentation.

Changes from V5:
 - Corrected an error found by yamllint in the documentation.

Changes from V4:
 - Added unit property to devicetree attribute making it now
   "poll-interval-ms".
 - Simplified logic for setting polled value and made variable names
   more clear.

Changes from V3:
 - After lengthy discussion decided to support with existing attribute
   of "poll-interval". If present, the driver will use polling and if
   not present, it will use triggered buffers (as the driver does
   today).
 - Corrected some lines to honor the 80 character line-limit.
 - Check return value from polling method and return early if there
   is an error reading the data.

Changes from V2:
 - Changed parameter from "adc-joystick,polled" to
   "adc-joystick,no-hardware-trigger" as it is more representative of
   what the driver and hardware are doing.

Changes from V1:
 - Removed driver compatible string of "adc-joystick-polled".
 - Added new optional boolean value of "adc-joystick,polled".
 - Cleaned up if statements regarding polling behavior.

Chris Morgan (3):
  dt-bindings: adc-joystick: add poll-interval
  Input: adc-joystick - Add polled input device support
  arm64: dts: rockchip: Update joystick to polled for OG2

 .../bindings/input/adc-joystick.yaml          |  5 ++
 .../boot/dts/rockchip/rk3326-odroid-go2.dts   |  1 +
 drivers/input/joystick/adc-joystick.c         | 82 ++++++++++++++-----
 3 files changed, 68 insertions(+), 20 deletions(-)

-- 
2.25.1

[PATCH v8 1/3] dt-bindings: adc-joystick: add poll-interval

[Chris Morgan]

From: Chris Morgan <macromorgan@hotmail.com>

Add poll-interval support for the adc-joystick documentation. This is
an optional value and if not provided the adc-joystick works as it
does today (with buffers). If this value is provided, the adc-joystick
driver is polled at the specified interval. The existing attribute of
"poll-interval" was used instead of complying with property-units.yaml
after discussion of the issue on the mailing list.

Signed-off-by: Maya Matuszczyk <maccraft123mc@gmail.com>
Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Artur Rojek <contact@artur-rojek.eu>
---
 Documentation/devicetree/bindings/input/adc-joystick.yaml | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/devicetree/bindings/input/adc-joystick.yaml b/Documentation/devicetree/bindings/input/adc-joystick.yaml
index 2ee04e03bc22..ab5caad055ea 100644
--- a/Documentation/devicetree/bindings/input/adc-joystick.yaml
+++ b/Documentation/devicetree/bindings/input/adc-joystick.yaml
@@ -14,6 +14,9 @@ description: >
   Bindings for joystick devices connected to ADC controllers supporting
   the Industrial I/O subsystem.
 
+allOf:
+  - $ref: input.yaml#
+
 properties:
   compatible:
     const: adc-joystick
@@ -28,6 +31,8 @@ properties:
       https://github.com/devicetree-org/dt-schema/blob/master/schemas/iio/iio-consumer.yaml
       for details.
 
+  poll-interval: true
+
   '#address-cells':
     const: 1
 
-- 
2.25.1

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

[Chris Morgan]

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(-)

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;
-- 
2.25.1

[PATCH v8 3/3] arm64: dts: rockchip: Update joystick to polled for OG2

[Chris Morgan]

From: Chris Morgan <macromorgan@hotmail.com>

Update the Odroid Go Advance to use "poll-interval" from the
adc-joystick driver.

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Signed-off-by: Maya Matuszczyk <maccraft123mc@gmail.com>
---
 arch/arm64/boot/dts/rockchip/rk3326-odroid-go2.dts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/boot/dts/rockchip/rk3326-odroid-go2.dts b/arch/arm64/boot/dts/rockchip/rk3326-odroid-go2.dts
index ea0695b51ecd..61583c3f24e6 100644
--- a/arch/arm64/boot/dts/rockchip/rk3326-odroid-go2.dts
+++ b/arch/arm64/boot/dts/rockchip/rk3326-odroid-go2.dts
@@ -26,6 +26,7 @@ adc-joystick {
 		compatible = "adc-joystick";
 		io-channels = <&saradc 1>,
 			      <&saradc 2>;
+		poll-interval = <60>;
 		#address-cells = <1>;
 		#size-cells = <0>;
 
-- 
2.25.1

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

[Artur Rojek]

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;

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

[Chris Morgan]

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;
> 

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

[Chris Morgan]

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;
> >