[PATCH] arm: sunxi: input: RFC: Add sysfs voltage for sun4i-lradc driver

---
 .../ABI/testing/sysfs-driver-input-sun4i-lradc     |  4 ++
 drivers/input/keyboard/sun4i-lradc-keys.c          | 49 +++++++++++++++++-----
 2 files changed, 43 insertions(+), 10 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc

diff --git a/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc b/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc
new file mode 100644
index 0000000..e4e6448
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc

@@ -0,0 +1,4 @@
+What:		/sys/class/input/input(x)/device/voltage
+Date:		February 2015
+Contact:	Priit Laes <plaes-q/aMd4JkU83YtjvyW6yDsg@public.gmane.org>
+Description:	ADC output voltage in microvolts or 0 if device is not opened.

diff --git a/drivers/input/keyboard/sun4i-lradc-keys.c b/drivers/input/keyboard/sun4i-lradc-keys.c
index cc8f7dd..c0ab8ec 100644
--- a/drivers/input/keyboard/sun4i-lradc-keys.c
+++ b/drivers/input/keyboard/sun4i-lradc-keys.c

@@ -79,10 +79,27 @@ struct sun4i_lradc_data {
 	u32 vref;
 };
 
+static u32 sun4i_lradc_read_voltage(struct sun4i_lradc_data *lradc)
+{
+	u32 val = readl(lradc->base + LRADC_DATA0) & 0x3f;
+	return val * lradc->vref / 63;
+};
+
+static ssize_t
+sun4i_lradc_dev_voltage_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct sun4i_lradc_data *lradc = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", sun4i_lradc_read_voltage(lradc));
+}
+
+static const DEVICE_ATTR(voltage, S_IRUGO, sun4i_lradc_dev_voltage_show, NULL);
+
 static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
 {
 	struct sun4i_lradc_data *lradc = dev_id;
-	u32 i, ints, val, voltage, diff, keycode = 0, closest = 0xffffffff;
+	u32 i, ints, voltage, diff, keycode = 0, closest = 0xffffffff;
 
 	ints  = readl(lradc->base + LRADC_INTS);
 

@@ -97,8 +114,7 @@ static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
 	}
 
 	if ((ints & CHAN0_KEYDOWN_IRQ) && lradc->chan0_keycode == 0) {
-		val = readl(lradc->base + LRADC_DATA0) & 0x3f;
-		voltage = val * lradc->vref / 63;
+		voltage = sun4i_lradc_read_voltage(lradc);
 
 		for (i = 0; i < lradc->chan0_map_count; i++) {
 			diff = abs(lradc->chan0_map[i].voltage - voltage);

@@ -156,7 +172,7 @@ static void sun4i_lradc_close(struct input_dev *dev)
 }
 
 static int sun4i_lradc_load_dt_keymap(struct device *dev,
-				      struct sun4i_lradc_data *lradc)
+				    struct sun4i_lradc_data *lradc)
 {
 	struct device_node *np, *pp;
 	int i;

@@ -168,8 +184,8 @@ static int sun4i_lradc_load_dt_keymap(struct device *dev,
 
 	lradc->chan0_map_count = of_get_child_count(np);
 	if (lradc->chan0_map_count == 0) {
-		dev_err(dev, "keymap is missing in device tree\n");
-		return -EINVAL;
+		dev_info(dev, "keymap is missing in device tree\n");
+		return 0;
 	}
 
 	lradc->chan0_map = devm_kmalloc_array(dev, lradc->chan0_map_count,

@@ -185,19 +201,19 @@ static int sun4i_lradc_load_dt_keymap(struct device *dev,
 
 		error = of_property_read_u32(pp, "channel", &channel);
 		if (error || channel != 0) {
-			dev_err(dev, "%s: Inval channel prop\n", pp->name);
+			dev_err(dev, "%s: Invalid 'channel' property\n", pp->name);
 			return -EINVAL;
 		}
 
 		error = of_property_read_u32(pp, "voltage", &map->voltage);
 		if (error) {
-			dev_err(dev, "%s: Inval voltage prop\n", pp->name);
+			dev_err(dev, "%s: Invalid 'voltage' property\n", pp->name);
 			return -EINVAL;
 		}
 
 		error = of_property_read_u32(pp, "linux,code", &map->keycode);
 		if (error) {
-			dev_err(dev, "%s: Inval linux,code prop\n", pp->name);
+			dev_err(dev, "%s: Invalid 'linux,code' property\n", pp->name);
 			return -EINVAL;
 		}
 

@@ -257,14 +273,26 @@ static int sun4i_lradc_probe(struct platform_device *pdev)
 	if (error)
 		return error;
 
-	error = input_register_device(lradc->input);
+	error = device_create_file(dev, &dev_attr_voltage);
 	if (error)
 		return error;
 
+	error = input_register_device(lradc->input);
+	if (error) {
+		device_remove_file(&pdev->dev, &dev_attr_voltage);
+		return error;
+	}
+
 	platform_set_drvdata(pdev, lradc);
 	return 0;
 }
 
+static int sun4i_lradc_remove(struct platform_device *pdev)
+{
+	device_remove_file(&pdev->dev, &dev_attr_voltage);
+	return 0;
+}
+
 static const struct of_device_id sun4i_lradc_of_match[] = {
 	{ .compatible = "allwinner,sun4i-a10-lradc-keys", },
 	{ /* sentinel */ }

@@ -277,6 +305,7 @@ static struct platform_driver sun4i_lradc_driver = {
 		.of_match_table = of_match_ptr(sun4i_lradc_of_match),
 	},
 	.probe	= sun4i_lradc_probe,
+	.remove = sun4i_lradc_remove,
 };
 
 module_platform_driver(sun4i_lradc_driver);

-- 
2.2.2

Hi,

On 26-01-15 17:58, Priit Laes wrote:

No commit message? Please write an informative commit msg, like why we want this patch,
I guess it is to help figuring out the voltage levels for various buttons when creating
a dts, but I would prefer to not guess, which is where a good commit message would
come in handy ...

Why this identation change ?

I assume this is so that people can still use the sysfs node, to create a dts, right
not sure I like this, might be better to document to simple create a dts with
a single button mapping for 200 mV (most board use 200 mV steps between the buttons).

This hunk / 3 changes belong in a separate patch. Also please run checkpatch, I think
you're running over 80 chars here.

This looks wrong, I think (*) that we've a bug here because we're not
unregistering the input device, so maybe do 2 patches, 1 fixing the
not unregistering bug, and then just add the device_remove_file()
in the sysfs patch.

  static const struct of_device_id sun4i_lradc_of_match[] = {
  	{ .compatible = "allwinner,sun4i-a10-lradc-keys", },
  	{ /* sentinel */ }

Regards,

Hans


*) But I'm not sure, better double check.

On Mon, Jan 26, 2015 at 08:28:29PM +0100, Hans de Goede wrote:

Hi,

On 26-01-15 17:58, Priit Laes wrote:

No commit message? Please write an informative commit msg, like why we want this patch,
I guess it is to help figuring out the voltage levels for various buttons when creating
a dts, but I would prefer to not guess, which is where a good commit message would
come in handy ...

quoted

---
 .../ABI/testing/sysfs-driver-input-sun4i-lradc     |  4 ++
 drivers/input/keyboard/sun4i-lradc-keys.c          | 49 +++++++++++++++++-----
 2 files changed, 43 insertions(+), 10 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc

diff --git a/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc b/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc
new file mode 100644
index 0000000..e4e6448
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc

@@ -0,0 +1,4 @@
+What:		/sys/class/input/input(x)/device/voltage
+Date:		February 2015
+Contact:	Priit Laes <plaes-q/aMd4JkU83YtjvyW6yDsg@public.gmane.org>
+Description:	ADC output voltage in microvolts or 0 if device is not opened.

diff --git a/drivers/input/keyboard/sun4i-lradc-keys.c b/drivers/input/keyboard/sun4i-lradc-keys.c
index cc8f7dd..c0ab8ec 100644
--- a/drivers/input/keyboard/sun4i-lradc-keys.c
+++ b/drivers/input/keyboard/sun4i-lradc-keys.c

@@ -79,10 +79,27 @@ struct sun4i_lradc_data {
 	u32 vref;
 };

+static u32 sun4i_lradc_read_voltage(struct sun4i_lradc_data *lradc)
+{
+	u32 val = readl(lradc->base + LRADC_DATA0) & 0x3f;
+	return val * lradc->vref / 63;
+};
+
+static ssize_t
+sun4i_lradc_dev_voltage_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct sun4i_lradc_data *lradc = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", sun4i_lradc_read_voltage(lradc));
+}
+
+static const DEVICE_ATTR(voltage, S_IRUGO, sun4i_lradc_dev_voltage_show, NULL);
+
 static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
 {
 	struct sun4i_lradc_data *lradc = dev_id;
-	u32 i, ints, val, voltage, diff, keycode = 0, closest = 0xffffffff;
+	u32 i, ints, voltage, diff, keycode = 0, closest = 0xffffffff;

 	ints  = readl(lradc->base + LRADC_INTS);

@@ -97,8 +114,7 @@ static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
 	}

 	if ((ints & CHAN0_KEYDOWN_IRQ) && lradc->chan0_keycode == 0) {
-		val = readl(lradc->base + LRADC_DATA0) & 0x3f;
-		voltage = val * lradc->vref / 63;
+		voltage = sun4i_lradc_read_voltage(lradc);

 		for (i = 0; i < lradc->chan0_map_count; i++) {
 			diff = abs(lradc->chan0_map[i].voltage - voltage);

@@ -156,7 +172,7 @@ static void sun4i_lradc_close(struct input_dev *dev)
 }

 static int sun4i_lradc_load_dt_keymap(struct device *dev,
-				      struct sun4i_lradc_data *lradc)
+				    struct sun4i_lradc_data *lradc)
 {
 	struct device_node *np, *pp;
 	int i;

Why this identation change ?

quoted

@@ -168,8 +184,8 @@ static int sun4i_lradc_load_dt_keymap(struct device *dev,

 	lradc->chan0_map_count = of_get_child_count(np);
 	if (lradc->chan0_map_count == 0) {
-		dev_err(dev, "keymap is missing in device tree\n");
-		return -EINVAL;
+		dev_info(dev, "keymap is missing in device tree\n");
+		return 0;
 	}

 	lradc->chan0_map = devm_kmalloc_array(dev, lradc->chan0_map_count,

I assume this is so that people can still use the sysfs node, to create a dts, right
not sure I like this, might be better to document to simple create a dts with
a single button mapping for 200 mV (most board use 200 mV steps between the buttons).

quoted

@@ -185,19 +201,19 @@ static int sun4i_lradc_load_dt_keymap(struct device *dev,

 		error = of_property_read_u32(pp, "channel", &channel);
 		if (error || channel != 0) {
-			dev_err(dev, "%s: Inval channel prop\n", pp->name);
+			dev_err(dev, "%s: Invalid 'channel' property\n", pp->name);
 			return -EINVAL;
 		}

 		error = of_property_read_u32(pp, "voltage", &map->voltage);
 		if (error) {
-			dev_err(dev, "%s: Inval voltage prop\n", pp->name);
+			dev_err(dev, "%s: Invalid 'voltage' property\n", pp->name);
 			return -EINVAL;
 		}

 		error = of_property_read_u32(pp, "linux,code", &map->keycode);
 		if (error) {
-			dev_err(dev, "%s: Inval linux,code prop\n", pp->name);
+			dev_err(dev, "%s: Invalid 'linux,code' property\n", pp->name);
 			return -EINVAL;
 		}

This hunk / 3 changes belong in a separate patch. Also please run checkpatch, I think
you're running over 80 chars here.

quoted

@@ -257,14 +273,26 @@ static int sun4i_lradc_probe(struct platform_device *pdev)
 	if (error)
 		return error;

-	error = input_register_device(lradc->input);
+	error = device_create_file(dev, &dev_attr_voltage);
 	if (error)
 		return error;

+	error = input_register_device(lradc->input);
+	if (error) {
+		device_remove_file(&pdev->dev, &dev_attr_voltage);
+		return error;
+	}
+
 	platform_set_drvdata(pdev, lradc);
 	return 0;
 }

+static int sun4i_lradc_remove(struct platform_device *pdev)
+{
+	device_remove_file(&pdev->dev, &dev_attr_voltage);
+	return 0;
+}
+

This looks wrong, I think (*) that we've a bug here because we're not
unregistering the input device, so maybe do 2 patches, 1 fixing the
not unregistering bug, and then just add the device_remove_file()
in the sysfs patch.

The unregister was not necessary since the input device is managed.

-- 
Dmitry

Hi,

On 26-01-15 23:06, Dmitry Torokhov wrote:

On Mon, Jan 26, 2015 at 08:28:29PM +0100, Hans de Goede wrote:

quoted

Hi,

On 26-01-15 17:58, Priit Laes wrote:

No commit message? Please write an informative commit msg, like why we want this patch,
I guess it is to help figuring out the voltage levels for various buttons when creating
a dts, but I would prefer to not guess, which is where a good commit message would
come in handy ...

quoted

---
  .../ABI/testing/sysfs-driver-input-sun4i-lradc     |  4 ++
  drivers/input/keyboard/sun4i-lradc-keys.c          | 49 +++++++++++++++++-----
  2 files changed, 43 insertions(+), 10 deletions(-)
  create mode 100644 Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc

diff --git a/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc b/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc
new file mode 100644
index 0000000..e4e6448
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc

@@ -0,0 +1,4 @@
+What:		/sys/class/input/input(x)/device/voltage
+Date:		February 2015
+Contact:	Priit Laes <plaes-q/aMd4JkU83YtjvyW6yDsg@public.gmane.org>
+Description:	ADC output voltage in microvolts or 0 if device is not opened.

diff --git a/drivers/input/keyboard/sun4i-lradc-keys.c b/drivers/input/keyboard/sun4i-lradc-keys.c
index cc8f7dd..c0ab8ec 100644
--- a/drivers/input/keyboard/sun4i-lradc-keys.c
+++ b/drivers/input/keyboard/sun4i-lradc-keys.c

@@ -79,10 +79,27 @@ struct sun4i_lradc_data {
  	u32 vref;
  };

+static u32 sun4i_lradc_read_voltage(struct sun4i_lradc_data *lradc)
+{
+	u32 val = readl(lradc->base + LRADC_DATA0) & 0x3f;
+	return val * lradc->vref / 63;
+};
+
+static ssize_t
+sun4i_lradc_dev_voltage_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct sun4i_lradc_data *lradc = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", sun4i_lradc_read_voltage(lradc));
+}
+
+static const DEVICE_ATTR(voltage, S_IRUGO, sun4i_lradc_dev_voltage_show, NULL);
+
  static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
  {
  	struct sun4i_lradc_data *lradc = dev_id;
-	u32 i, ints, val, voltage, diff, keycode = 0, closest = 0xffffffff;
+	u32 i, ints, voltage, diff, keycode = 0, closest = 0xffffffff;

  	ints  = readl(lradc->base + LRADC_INTS);

@@ -97,8 +114,7 @@ static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
  	}

  	if ((ints & CHAN0_KEYDOWN_IRQ) && lradc->chan0_keycode == 0) {
-		val = readl(lradc->base + LRADC_DATA0) & 0x3f;
-		voltage = val * lradc->vref / 63;
+		voltage = sun4i_lradc_read_voltage(lradc);

  		for (i = 0; i < lradc->chan0_map_count; i++) {
  			diff = abs(lradc->chan0_map[i].voltage - voltage);

@@ -156,7 +172,7 @@ static void sun4i_lradc_close(struct input_dev *dev)
  }

  static int sun4i_lradc_load_dt_keymap(struct device *dev,
-				      struct sun4i_lradc_data *lradc)
+				    struct sun4i_lradc_data *lradc)
  {
  	struct device_node *np, *pp;
  	int i;

Why this identation change ?

quoted

@@ -168,8 +184,8 @@ static int sun4i_lradc_load_dt_keymap(struct device *dev,

  	lradc->chan0_map_count = of_get_child_count(np);
  	if (lradc->chan0_map_count == 0) {
-		dev_err(dev, "keymap is missing in device tree\n");
-		return -EINVAL;
+		dev_info(dev, "keymap is missing in device tree\n");
+		return 0;
  	}

  	lradc->chan0_map = devm_kmalloc_array(dev, lradc->chan0_map_count,

I assume this is so that people can still use the sysfs node, to create a dts, right
not sure I like this, might be better to document to simple create a dts with
a single button mapping for 200 mV (most board use 200 mV steps between the buttons).

quoted

@@ -185,19 +201,19 @@ static int sun4i_lradc_load_dt_keymap(struct device *dev,

  		error = of_property_read_u32(pp, "channel", &channel);
  		if (error || channel != 0) {
-			dev_err(dev, "%s: Inval channel prop\n", pp->name);
+			dev_err(dev, "%s: Invalid 'channel' property\n", pp->name);
  			return -EINVAL;
  		}

  		error = of_property_read_u32(pp, "voltage", &map->voltage);
  		if (error) {
-			dev_err(dev, "%s: Inval voltage prop\n", pp->name);
+			dev_err(dev, "%s: Invalid 'voltage' property\n", pp->name);
  			return -EINVAL;
  		}

  		error = of_property_read_u32(pp, "linux,code", &map->keycode);
  		if (error) {
-			dev_err(dev, "%s: Inval linux,code prop\n", pp->name);
+			dev_err(dev, "%s: Invalid 'linux,code' property\n", pp->name);
  			return -EINVAL;
  		}

This hunk / 3 changes belong in a separate patch. Also please run checkpatch, I think
you're running over 80 chars here.

quoted

@@ -257,14 +273,26 @@ static int sun4i_lradc_probe(struct platform_device *pdev)
  	if (error)
  		return error;

-	error = input_register_device(lradc->input);
+	error = device_create_file(dev, &dev_attr_voltage);
  	if (error)
  		return error;

+	error = input_register_device(lradc->input);
+	if (error) {
+		device_remove_file(&pdev->dev, &dev_attr_voltage);
+		return error;
+	}
+
  	platform_set_drvdata(pdev, lradc);
  	return 0;
  }

+static int sun4i_lradc_remove(struct platform_device *pdev)
+{
+	device_remove_file(&pdev->dev, &dev_attr_voltage);
+	return 0;
+}
+

This looks wrong, I think (*) that we've a bug here because we're not
unregistering the input device, so maybe do 2 patches, 1 fixing the
not unregistering bug, and then just add the device_remove_file()
in the sysfs patch.

The unregister was not necessary since the input device is managed.

Ah right, looking at the code again I see we use devm_input_allocate_device()
is there no devm_create_file for creating sysfs entries ?

Regards,

Hans

Hi,

On Mon, Jan 26, 2015 at 06:58:32PM +0200, Priit Laes wrote:

---

Like Hans was pointing out, commit log and signed-off-by please

Why is it returning 0 when "device is not opened" ? What does that
even mean? You can't read that file without opening it.

As I told you already, if you're going to expose this an ADC in the
end, the proper solution is to use the IIO framework, not adding a
custom sysfs file.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

On Tue, Jan 27, 2015 at 10:03:35AM +0100, Hans de Goede wrote:

Hi,

On 26-01-15 23:06, Dmitry Torokhov wrote:

quoted

On Mon, Jan 26, 2015 at 08:28:29PM +0100, Hans de Goede wrote:

quoted

Hi,

On 26-01-15 17:58, Priit Laes wrote:

No commit message? Please write an informative commit msg, like why we want this patch,
I guess it is to help figuring out the voltage levels for various buttons when creating
a dts, but I would prefer to not guess, which is where a good commit message would
come in handy ...

quoted

---
 .../ABI/testing/sysfs-driver-input-sun4i-lradc     |  4 ++
 drivers/input/keyboard/sun4i-lradc-keys.c          | 49 +++++++++++++++++-----
 2 files changed, 43 insertions(+), 10 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc

diff --git a/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc b/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc
new file mode 100644
index 0000000..e4e6448
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc

@@ -0,0 +1,4 @@
+What:		/sys/class/input/input(x)/device/voltage
+Date:		February 2015
+Contact:	Priit Laes <plaes-q/aMd4JkU83YtjvyW6yDsg@public.gmane.org>
+Description:	ADC output voltage in microvolts or 0 if device is not opened.

diff --git a/drivers/input/keyboard/sun4i-lradc-keys.c b/drivers/input/keyboard/sun4i-lradc-keys.c
index cc8f7dd..c0ab8ec 100644
--- a/drivers/input/keyboard/sun4i-lradc-keys.c
+++ b/drivers/input/keyboard/sun4i-lradc-keys.c

@@ -79,10 +79,27 @@ struct sun4i_lradc_data {
 	u32 vref;
 };

+static u32 sun4i_lradc_read_voltage(struct sun4i_lradc_data *lradc)
+{
+	u32 val = readl(lradc->base + LRADC_DATA0) & 0x3f;
+	return val * lradc->vref / 63;
+};
+
+static ssize_t
+sun4i_lradc_dev_voltage_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct sun4i_lradc_data *lradc = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", sun4i_lradc_read_voltage(lradc));
+}
+
+static const DEVICE_ATTR(voltage, S_IRUGO, sun4i_lradc_dev_voltage_show, NULL);
+
 static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
 {
 	struct sun4i_lradc_data *lradc = dev_id;
-	u32 i, ints, val, voltage, diff, keycode = 0, closest = 0xffffffff;
+	u32 i, ints, voltage, diff, keycode = 0, closest = 0xffffffff;

 	ints  = readl(lradc->base + LRADC_INTS);

@@ -97,8 +114,7 @@ static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
 	}

 	if ((ints & CHAN0_KEYDOWN_IRQ) && lradc->chan0_keycode == 0) {
-		val = readl(lradc->base + LRADC_DATA0) & 0x3f;
-		voltage = val * lradc->vref / 63;
+		voltage = sun4i_lradc_read_voltage(lradc);

 		for (i = 0; i < lradc->chan0_map_count; i++) {
 			diff = abs(lradc->chan0_map[i].voltage - voltage);

@@ -156,7 +172,7 @@ static void sun4i_lradc_close(struct input_dev *dev)
 }

 static int sun4i_lradc_load_dt_keymap(struct device *dev,
-				      struct sun4i_lradc_data *lradc)
+				    struct sun4i_lradc_data *lradc)
 {
 	struct device_node *np, *pp;
 	int i;

Why this identation change ?

quoted

@@ -168,8 +184,8 @@ static int sun4i_lradc_load_dt_keymap(struct device *dev,

 	lradc->chan0_map_count = of_get_child_count(np);
 	if (lradc->chan0_map_count == 0) {
-		dev_err(dev, "keymap is missing in device tree\n");
-		return -EINVAL;
+		dev_info(dev, "keymap is missing in device tree\n");
+		return 0;
 	}

 	lradc->chan0_map = devm_kmalloc_array(dev, lradc->chan0_map_count,

I assume this is so that people can still use the sysfs node, to create a dts, right
not sure I like this, might be better to document to simple create a dts with
a single button mapping for 200 mV (most board use 200 mV steps between the buttons).

quoted

@@ -185,19 +201,19 @@ static int sun4i_lradc_load_dt_keymap(struct device *dev,

 		error = of_property_read_u32(pp, "channel", &channel);
 		if (error || channel != 0) {
-			dev_err(dev, "%s: Inval channel prop\n", pp->name);
+			dev_err(dev, "%s: Invalid 'channel' property\n", pp->name);
 			return -EINVAL;
 		}

 		error = of_property_read_u32(pp, "voltage", &map->voltage);
 		if (error) {
-			dev_err(dev, "%s: Inval voltage prop\n", pp->name);
+			dev_err(dev, "%s: Invalid 'voltage' property\n", pp->name);
 			return -EINVAL;
 		}

 		error = of_property_read_u32(pp, "linux,code", &map->keycode);
 		if (error) {
-			dev_err(dev, "%s: Inval linux,code prop\n", pp->name);
+			dev_err(dev, "%s: Invalid 'linux,code' property\n", pp->name);
 			return -EINVAL;
 		}

This hunk / 3 changes belong in a separate patch. Also please run checkpatch, I think
you're running over 80 chars here.

quoted

@@ -257,14 +273,26 @@ static int sun4i_lradc_probe(struct platform_device *pdev)
 	if (error)
 		return error;

-	error = input_register_device(lradc->input);
+	error = device_create_file(dev, &dev_attr_voltage);
 	if (error)
 		return error;

+	error = input_register_device(lradc->input);
+	if (error) {
+		device_remove_file(&pdev->dev, &dev_attr_voltage);
+		return error;
+	}
+
 	platform_set_drvdata(pdev, lradc);
 	return 0;
 }

+static int sun4i_lradc_remove(struct platform_device *pdev)
+{
+	device_remove_file(&pdev->dev, &dev_attr_voltage);
+	return 0;
+}
+

This looks wrong, I think (*) that we've a bug here because we're not
unregistering the input device, so maybe do 2 patches, 1 fixing the
not unregistering bug, and then just add the device_remove_file()
in the sysfs patch.

The unregister was not necessary since the input device is managed.

Ah right, looking at the code again I see we use devm_input_allocate_device()
is there no devm_create_file for creating sysfs entries ?

Greg was pushing the viewpoint that no drivers should create device attributes
manually (since it is somewhat racy - attributes are created after devices show
up) but I do not think he's gonna win that ever. So if someone were to add
devm_create_attribute_group() API I think that would be great. In absence of
this there is always devm_add_action().

Thanks.

-- 
Dmitry