Re: [PATCH v4 2/3] Input: gpio_keys.c: Added support for device-tree platform data

Hi Grant,

On Thu, 16 Jun 2011 13:25:59 -0600
Grant Likely [off-list ref] wrote:

On Tue, Jun 14, 2011 at 11:08:10AM +0200, David Jander wrote:

quoted

This patch enables fetching configuration data which is normally provided
via platform_data from the device-tree instead.
If the device is configured from device-tree data, the platform_data struct
is not used, and button data needs to be allocated dynamically.
Big part of this patch deals with confining pdata usage to the probe
function, to make this possible.

Signed-off-by: David Jander <redacted>
---
 .../devicetree/bindings/gpio/gpio_keys.txt         |   49 +++++++
 drivers/input/keyboard/gpio_keys.c                 |  147
++++++++++++++++++-- 2 files changed, 186 insertions(+), 10 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio_keys.txt

diff --git a/Documentation/devicetree/bindings/gpio/gpio_keys.txt

b/Documentation/devicetree/bindings/gpio/gpio_keys.txt new file mode 100644
index 0000000..60a4d8e

--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio_keys.txt

@@ -0,0 +1,49 @@
+Device-Tree bindings for input/gpio_keys.c keyboard driver
+
+Required properties:
+	- compatible = "gpio-keys";
+
+Optional properties:
+	- autorepeat: Boolean, Enable auto repeat feature of Linux input
+	  subsystem.
+
+Each button (key) is represented as a sub-node of "gpio-keys":
+Subnode properties:
+
+	- reg: GPIO number the key is bound to if linux GPIO numbering is

used.

Wait.  That won't work.  There is no concept of "linux gpio numbering"
in the device tree data.  When using device tree, the gpio numbers
usually get dynamically assigned.

Yes I know, but suppose you want to use this driver with a GPIO-driver that
does not have devaice-tree support yet? I need a way of binding the button to
a GPIO pin that does not have a device-tree definition. How should I do this
otherwise?
I am using this driver with a pca963x, as you might have suspected already,
and I just added OF device-tree support to it, so that will work, but
others...?
Before "fixing" pca963x, I used this property and it worked perfectly well, so
please explain what is not supposed to work. Please keep in mind that this
is meant as more of a backwards-compatibility feature. If you think that being
backwards compatible with non-OF GPIO drivers is a bad idea, I'll remove this.

quoted

+	- gpios: OF devcie-tree gpio specification, can be used
alternatively
+	  if 'reg' is not specified, to use device-tree GPIOs.
+	- label: Descriptive name of the key.
+	- linux,code: Keycode to emit.
+
+Optional subnode-properties:
+	- active-low: Boolean flag to specify active-low GPIO input. Not
used
+	  if device-tree gpios property is used.
+	- linux,input-type: Specify event type this button/key generates.
+	  Default if unspecified is <1> == EV_KEY.
+	- debounce-interval: Debouncing interval time in milliseconds.
+	  Default if unspecified is 5.
+	- wakeup: Boolean, button can wake-up the system.

"wakeup" is potentially too generic a property name (potential to
conflict with a generic wakeup binding if one ever exists).  Just to
be defencive, I'd suggest prefixing these custom gpio keys properties
with something like "gpio-key,".

Ok, "gpio-key,wakeup" it will be then? But isn't this function something
potentially other IO-pins/keys/buttons/interrupts/etc... could have to be able
to wake up the system?

quoted

+
+Example nodes:
+
+	gpio_keys {
+			compatible = "gpio-keys";
+			#address-cells = <1>;
+			#size-cells = <0>;
+			autorepeat;
+			button@20 {
+				label = "GPIO Key ESC";
+				linux,code = <1>;
+				reg = <0x20>;
+				key-active-low;
+				linux,input-type = <1>;
+			};
+			button@21 {
+				label = "GPIO Key UP";
+				linux,code = <103>;
+				gpios = <&gpio1 0 1>;
+				linux,input-type = <1>;
+			};
+			...
+

diff --git a/drivers/input/keyboard/gpio_keys.c

b/drivers/input/keyboard/gpio_keys.c index 987498e..78aeeaa 100644

--- a/drivers/input/keyboard/gpio_keys.c
+++ b/drivers/input/keyboard/gpio_keys.c

@@ -3,6 +3,9 @@
  *
  * Copyright 2005 Phil Blundell
  *
+ * Added OF support:
+ * Copyright 2010 David Jander <david@protonic.nl>
+ *

But it's 2011!  :-)

Ooops :-) You see... this patch is rather old already (in my tree). I actually
wrote it in 2010, but I am submitting it now. I guess it should be "2010, 2011"
then?

quoted

  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.

@@ -25,6 +28,8 @@
 #include <linux/gpio_keys.h>
 #include <linux/workqueue.h>
 #include <linux/gpio.h>
+#include <linux/of_platform.h>
+#include <linux/of_gpio.h>
 
 struct gpio_button_data {
 	struct gpio_keys_button *button;

@@ -442,15 +447,124 @@ static void gpio_keys_close(struct input_dev *input)
 		ddata->disable(input->dev.parent);
 }
 
+/*
+ * Handlers for alternative sources of platform_data
+ */
+#ifdef CONFIG_OF
+/*
+ * Translate OpenFirmware node properties into platform_data
+ */
+static struct gpio_keys_platform_data *
+gpio_keys_get_devtree_pdata(struct device *dev,
+			    struct gpio_keys_platform_data *altp)
+{
+	struct gpio_keys_platform_data *pdata = altp;

pdata is always the same as altp.

Ok, right.

You don't need this on the stack, and the return value should be an error
code instead of a pointer because the pointer is already passed in!

Hmm... I was (mis-)using the returned pointer as an error code. Will try to
come up with something more sensible.

quoted

+	struct device_node *node, *pp;
+	int i;
+	struct gpio_keys_button *buttons;
+	const u32 *reg;
+	int len;
+
+	node = dev->of_node;
+	if (node == NULL)
+		return NULL;
+
+	memset(pdata, 0, sizeof *pdata);
+
+	pdata->rep = !!of_get_property(node, "autorepeat", &len);
+
+	/* First count the subnodes */
+	pdata->nbuttons = 0;
+	pp = NULL;
+	while ((pp = of_get_next_child(node, pp)))
+		pdata->nbuttons++;
+
+	if (pdata->nbuttons == 0)
+		return NULL;
+
+	buttons = kzalloc(pdata->nbuttons * (sizeof *buttons),
GFP_KERNEL);
+	if (!buttons)
+		return NULL;
+
+	pp = NULL;
+	i = 0;
+	while ((pp = of_get_next_child(node, pp))) {
+		const char *lbl;
+		enum of_gpio_flags flags;
+
+		reg = of_get_property(pp, "reg", &len);
+		if (!reg && !of_find_property(pp, "gpios", NULL)) {
+			pdata->nbuttons--;
+			dev_warn(dev, "Found button without reg and
without gpios\n");
+			continue;
+		}
+		if (reg) {
+			buttons[i].gpio = be32_to_cpup(reg);

As mentioned above, this won't work.  Linux gpio numbers cannot be
encoded into the DT.

Why not? It worked fine for me before I "fixed" pca963x.
If you have a non-OF GPIO controller, that one will need a numeric range of
GPIO numbers. If that range is fixed, I can perfectly well give this number to
the driver here.... again, this is only used if the GPIO driver does not
have a device-tree node.

quoted

+			buttons[i].active_low = !!of_get_property(pp,
"key-active-low", NULL);
+		} else {
+			buttons[i].gpio = of_get_gpio_flags(pp, 0,
&flags);
+			buttons[i].active_low = !!(flags &
OF_GPIO_ACTIVE_LOW);
+		}
+
+		reg = of_get_property(pp, "linux,code", &len);
+		if (!reg) {
+			dev_err(dev, "Button without keycode: 0x%x\n",
buttons[i].gpio);
+			goto out_fail;
+		}
+		buttons[i].code = be32_to_cpup(reg);
+
+		lbl = of_get_property(pp, "label", &len);
+		buttons[i].desc = (char *)lbl;
+
+		reg = of_get_property(pp, "linux,input-type", &len);
+		if (reg)
+			buttons[i].type = be32_to_cpup(reg);
+		else
+			buttons[i].type = EV_KEY;

how about:
		buttons[i].type = reg ? be32_to_cpup(reg) : EV_KEY;

Ok, if you prefer this notation.... just an "if...else" in another dress ;-)

quoted

+
+		buttons[i].wakeup = !!of_get_property(pp, "wakeup", NULL);
+
+		reg = of_get_property(pp, "debounce-interval", &len);
+		if (reg)
+			buttons[i].debounce_interval = be32_to_cpup(reg);
+		else
+			buttons[i].debounce_interval = 5;

Ditto here.

Ok, as you wish.

quoted

+		i++;
+	}
+
+	pdata->buttons = buttons;
+
+	return pdata;
+
+out_fail:
+	kfree(buttons);
+	return NULL;
+}
+#else
+static struct gpio_keys_platform_data *
+gpio_keys_get_devtree_pdata(struct device *dev,
+			    struct gpio_keys_platform_data *altp)
+{
+	return NULL;
+}
+#endif
+
 static int __devinit gpio_keys_probe(struct platform_device *pdev)
 {
 	struct gpio_keys_drvdata *ddata;
 	struct device *dev = &pdev->dev;
 	struct gpio_keys_platform_data *pdata = dev->platform_data;
+	struct gpio_keys_platform_data alt_pdata;
 	struct input_dev *input;
 	int i, error;
 	int wakeup = 0;
 
+	if (!pdata) {
+		pdata = gpio_keys_get_devtree_pdata(dev, &alt_pdata);
+		if (!pdata)
+			return -ENODEV;
+	}

then this would become:

	if (!pdata) {
		rc = gpio_keys_get_devtree_pdata(dev, &alt_pdata);
		if (rc)
			return rc;
		pdata = &alt_pdata;
	}

Yes, of course. I just need to "invent" which error codes to use for the
different failure cases.... no problem.

quoted

+
 	ddata = kzalloc(sizeof(struct gpio_keys_drvdata) +
 			pdata->nbuttons * sizeof(struct gpio_button_data),
 			GFP_KERNEL);

@@ -548,7 +662,6 @@ static int __devinit gpio_keys_probe(struct

platform_device *pdev) static int __devexit gpio_keys_remove(struct
platform_device *pdev) {
 	struct device *dev = &pdev->dev;
-	struct gpio_keys_platform_data *pdata = dev->platform_data;
 	struct gpio_keys_drvdata *ddata = dev_get_drvdata(dev);
 	struct input_dev *input = ddata->input;
 	int i;

@@ -557,30 +670,42 @@ static int __devexit gpio_keys_remove(struct

platform_device *pdev) 
 	device_init_wakeup(dev, 0);
 
-	for (i = 0; i < pdata->nbuttons; i++) {
-		int irq = gpio_to_irq(pdata->buttons[i].gpio);
+	for (i = 0; i < ddata->n_buttons; i++) {
+		int irq = gpio_to_irq(ddata->data[i].button->gpio);
 		free_irq(irq, &ddata->data[i]);
 		if (ddata->data[i].timer_debounce)
 			del_timer_sync(&ddata->data[i].timer);
 		cancel_work_sync(&ddata->data[i].work);
-		gpio_free(pdata->buttons[i].gpio);
+		gpio_free(ddata->data[i].button->gpio);
 	}
 
+	/*
+	 * If we had no platform_data, we allocated buttons dynamically,
and
+	 * must free them here. ddata->data[0].button is the pointer to
the
+	 * beginning of the allocated array.
+	 */
+	if (!dev->platform_data)
+		kfree(ddata->data[0].button);
+
 	input_unregister_device(input);
 
 	return 0;
 }
 
+static struct of_device_id gpio_keys_of_match[] = {
+	{ .compatible = "gpio-keys", },
+	{},
+};
 
 #ifdef CONFIG_PM
 static int gpio_keys_suspend(struct device *dev)
 {
-	struct gpio_keys_platform_data *pdata = dev->platform_data;
+	struct gpio_keys_drvdata *ddata = dev_get_drvdata(dev);
 	int i;
 
 	if (device_may_wakeup(dev)) {
-		for (i = 0; i < pdata->nbuttons; i++) {
-			struct gpio_keys_button *button =
&pdata->buttons[i];
+		for (i = 0; i < ddata->n_buttons; i++) {
+			struct gpio_keys_button *button =
ddata->data[i].button; if (button->wakeup) {
 				int irq = gpio_to_irq(button->gpio);
 				enable_irq_wake(irq);

@@ -594,12 +719,11 @@ static int gpio_keys_suspend(struct device *dev)
 static int gpio_keys_resume(struct device *dev)
 {
 	struct gpio_keys_drvdata *ddata = dev_get_drvdata(dev);
-	struct gpio_keys_platform_data *pdata = dev->platform_data;
 	int i;
 
-	for (i = 0; i < pdata->nbuttons; i++) {
+	for (i = 0; i < ddata->n_buttons; i++) {
 
-		struct gpio_keys_button *button = &pdata->buttons[i];
+		struct gpio_keys_button *button = ddata->data[i].button;
 		if (button->wakeup && device_may_wakeup(dev)) {
 			int irq = gpio_to_irq(button->gpio);
 			disable_irq_wake(irq);

@@ -618,6 +742,8 @@ static const struct dev_pm_ops gpio_keys_pm_ops = {
 };
 #endif
 
+MODULE_DEVICE_TABLE(of, gpio_keys_of_match);
+

Modules device table needs to be #ifdef CONFIG_OF protected.
Otherwise the driver advertises behaviour that it cannot provide.

Ah, ok. Will add an #ifdef. Thanks for pointing out.

Best regards,

-- 
David Jander
Protonic Holland.