[PATCH v2 0/6] Introduce deferred probing

[PATCH v2 0/6] Introduce deferred probing

[Sebastian Hesselbarth]

This is round two of the introduction of deferred probing by moving
drivers that request probe deferral to an extra device list that will
be re-probed later.

Compared to v1 there are the following changes:
- Loop over deferred device list until none succeeds
  (Suggested by Sascha Hauer)
- (Now) properly deal with deferred probing in led-gpio
- Free GPIOs claimed by leds on foo_led_unregister()
- Convert Orion GPIO to real platform driver
Each patch also contains an individual changelog.

It would be great to give this patch series a little more coverage.
Also, several other subsystems could use some support -EPROBE_DEFER
but IMHO we should wait for someone to actually force probe deferral
there.

Sebastian Hesselbarth (6):
  base: Introduce deferred probing
  gpio: Return -EPROBE_DEFER on gpio_get_num()
  OF: gpio: Silence error message on -EPROBE_DEFER
  led: gpio: Properly deal with deferred probing
  led: gpio: Free GPIOs on unregister()
  gpio: orion: Convert to platform_driver

 drivers/base/driver.c       | 56 ++++++++++++++++++++++++++++++++++++++++++---
 drivers/gpio/gpio-orion.c   |  7 +-----
 drivers/gpio/gpiolib.c      |  5 +++-
 drivers/led/led-gpio.c      | 36 +++++++++++++++++++++++++----
 drivers/of/of_gpio.c        |  8 ++++---
 include/asm-generic/errno.h |  1 +
 6 files changed, 96 insertions(+), 17 deletions(-)

---
Cc: barebox@lists.infradead.org
-- 
2.1.0


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[PATCH v2 1/6] base: Introduce deferred probing

[Sebastian Hesselbarth]

As expected, we would need deferred probing sooner or later. This is
a first approach to allow devices to return -EPROBE_DEFER and get
sorted into a list of deferred devices that will be re-probed later.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
---
Changelog:
v1->v2:
- Rework deferred probing to loop until no previously deferred device
  probing succeeds. (Suggested by Sascha Hauer)
- Print an error message for devices stuck in deferred list.
- Add a comment how deferred probing and re-assignment to deferred
  list works.

Cc: barebox@lists.infradead.org
---
 drivers/base/driver.c       | 56 ++++++++++++++++++++++++++++++++++++++++++---
 include/asm-generic/errno.h |  1 +
 2 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/drivers/base/driver.c b/drivers/base/driver.c
index 590c97c96424..6112b4953ba6 100644
--- a/drivers/base/driver.c
+++ b/drivers/base/driver.c
@@ -29,6 +29,7 @@
 #include <console.h>
 #include <linux/ctype.h>
 #include <errno.h>
+#include <init.h>
 #include <fs.h>
 #include <of.h>
 #include <linux/list.h>
@@ -43,6 +44,7 @@ LIST_HEAD(driver_list);
 EXPORT_SYMBOL(driver_list);
 
 static LIST_HEAD(active);
+static LIST_HEAD(deferred);
 
 struct device_d *get_device_by_name(const char *name)
 {
@@ -88,13 +90,20 @@ int device_probe(struct device_d *dev)
 	list_add(&dev->active, &active);
 
 	ret = dev->bus->probe(dev);
-	if (ret) {
+	if (ret == 0)
+		return 0;
+
+	if (ret == -EPROBE_DEFER) {
 		list_del(&dev->active);
-		dev_err(dev, "probe failed: %s\n", strerror(-ret));
+		list_add(&dev->active, &deferred);
+		dev_dbg(dev, "probe deferred\n");
 		return ret;
 	}
 
-	return 0;
+	list_del(&dev->active);
+	dev_err(dev, "probe failed: %s\n", strerror(-ret));
+
+	return ret;
 }
 
 int device_detect(struct device_d *dev)
@@ -213,6 +222,47 @@ int unregister_device(struct device_d *old_dev)
 }
 EXPORT_SYMBOL(unregister_device);
 
+/*
+ * Loop over list of deferred devices as long as at least one
+ * device is successfully probed. Devices that again request
+ * deferral are re-added to deferred list in device_probe().
+ * For devices finally left in deferred list -EPROBE_DEFER
+ * becomes a fatal error.
+ */
+static int device_probe_deferred(void)
+{
+	struct device_d *dev, *tmp;
+	struct driver_d *drv;
+	bool success;
+
+	do {
+		success = false;
+
+		if (list_empty(&deferred))
+			break;
+
+		list_for_each_entry_safe(dev, tmp, &deferred, active) {
+			list_del(&dev->active);
+			dev_dbg(dev, "re-probe device\n");
+			bus_for_each_driver(dev->bus, drv) {
+				if (match(drv, dev))
+					continue;
+				success = true;
+				break;
+			}
+		}
+	} while (success);
+
+	if (list_empty(&deferred))
+		return 0;
+
+	list_for_each_entry(dev, &deferred, active)
+		dev_err(dev, "probe permanently deferred\n");
+
+	return 0;
+}
+late_initcall(device_probe_deferred);
+
 struct driver_d *get_driver_by_name(const char *name)
 {
 	struct driver_d *drv;
diff --git a/include/asm-generic/errno.h b/include/asm-generic/errno.h
index bbf493c373ae..6072f7b605bb 100644
--- a/include/asm-generic/errno.h
+++ b/include/asm-generic/errno.h
@@ -132,6 +132,7 @@
 #define ERESTARTNOINTR	513
 #define ERESTARTNOHAND	514	/* restart if no handler.. */
 #define ENOIOCTLCMD	515	/* No ioctl command */
+#define EPROBE_DEFER	517	/* Driver requests probe retry */
 
 #define ENOTSUPP	524	/* Operation is not supported */
 
-- 
2.1.0


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[PATCH v2 2/6] gpio: Return -EPROBE_DEFER on gpio_get_num()

[Sebastian Hesselbarth]

GPIO drivers can be registered quite late in registration process
causing dependant devices to fail probing. If we know gpio_get_num
will be called with a non-NULL device, return -EPROBE_DEFER instead
of -ENODEV to allow re-probing later.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
---
Changelog:
v1->v2:
- none

Cc: barebox@lists.infradead.org
---
 drivers/gpio/gpiolib.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 611e41ea5606..1f57c76ec16d 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -292,12 +292,15 @@ int gpio_get_num(struct device_d *dev, int gpio)
 {
 	struct gpio_chip *chip;
 
+	if (!dev)
+		return -ENODEV;
+
 	list_for_each_entry(chip, &chip_list, list) {
 		if (chip->dev == dev)
 			return chip->base + gpio;
 	}
 
-	return -ENODEV;
+	return -EPROBE_DEFER;
 }
 
 #ifdef CONFIG_CMD_GPIO
-- 
2.1.0


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[PATCH v2 3/6] OF: gpio: Silence error message on -EPROBE_DEFER

[Sebastian Hesselbarth]

With deferred probing, -EPROBE_DEFER is not worth spilling an error.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
---
Changelog:
v1->v2:
- Also return early on gpio_get_num() == -EPROBE_DEFER

Cc: barebox@lists.infradead.org
---
 drivers/of/of_gpio.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/of/of_gpio.c b/drivers/of/of_gpio.c
index 6738a220a5a3..dc8ae2277641 100644
--- a/drivers/of/of_gpio.c
+++ b/drivers/of/of_gpio.c
@@ -32,12 +32,14 @@ int of_get_named_gpio_flags(struct device_node *np, const char *propname,
 
 	dev = of_find_device_by_node(out_args.np);
 	if (!dev) {
-		pr_err("%s: unable to find device of node %s\n",
-			__func__, out_args.np->full_name);
-		return -ENODEV;
+		pr_debug("%s: unable to find device of node %s\n",
+			 __func__, out_args.np->full_name);
+		return -EPROBE_DEFER;
 	}
 
 	ret = gpio_get_num(dev, out_args.args[0]);
+	if (ret == -EPROBE_DEFER)
+		return ret;
 	if (ret < 0) {
 		pr_err("%s: unable to get gpio num of device %s: %d\n",
 			__func__, dev_name(dev), ret);
-- 
2.1.0


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[PATCH v2 4/6] led: gpio: Properly deal with deferred probing

[Sebastian Hesselbarth]

GPIO LEDs can suffer from deferred probing due to failing gpio request.
Instead of registering each gpio led independently, pre-allocate an
array of struct gpio_led for all and tear it down properly if probing
of one leds fails. While at it, silence error messages on -EPROBE_DEFER.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
---
Changelog:
v1->v2:
- Drop static registered bitmap as two "gpio-leds" nodes will both
  call led_gpio_of_probe(). The second call will find the static
  variable modified and skip some leds.
- Use a pre-allocated array of struct gpio_led instead that will
  be torn down on failure.

Cc: barebox@lists.infradead.org
---
 drivers/led/led-gpio.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/led/led-gpio.c b/drivers/led/led-gpio.c
index ae3f13f45b6c..807251721fd3 100644
--- a/drivers/led/led-gpio.c
+++ b/drivers/led/led-gpio.c
@@ -20,6 +20,7 @@
 #include <common.h>
 #include <init.h>
 #include <led.h>
+#include <malloc.h>
 #include <gpio.h>
 #include <of_gpio.h>
 
@@ -201,19 +202,32 @@ void led_gpio_rgb_unregister(struct gpio_led *led)
 static int led_gpio_of_probe(struct device_d *dev)
 {
 	struct device_node *child;
+	struct gpio_led *leds;
+	int num_leds;
+	int ret = 0, n = 0;
+
+	num_leds = of_get_child_count(dev->device_node);
+	if (num_leds <= 0)
+		return num_leds;
+
+	leds = xzalloc(num_leds * sizeof(struct gpio_led));
 
 	for_each_child_of_node(dev->device_node, child) {
-		struct gpio_led *gled;
+		struct gpio_led *gled = &leds[n];
 		const char *default_state;
 		enum of_gpio_flags flags;
 		int gpio;
 		const char *label;
 
 		gpio = of_get_named_gpio_flags(child, "gpios", 0, &flags);
-		if (gpio < 0)
-			continue;
+		if (gpio < 0) {
+			if (gpio != -EPROBE_DEFER)
+				dev_err(dev, "failed to get gpio for %s: %d\n",
+					child->full_name, gpio);
+			ret = gpio;
+			goto err;
+		}
 
-		gled = xzalloc(sizeof(*gled));
 		if (of_property_read_string(child, "label", &label))
 			label = child->name;
 		gled->led.name = xstrdup(label);
@@ -233,9 +247,17 @@ static int led_gpio_of_probe(struct device_d *dev)
 			else if (!strcmp(default_state, "off"))
 				led_gpio_set(&gled->led, 0);
 		}
+
+		n++;
 	}
 
 	return 0;
+
+err:
+	for (n = n - 1; n >= 0; n--)
+		led_gpio_unregister(&leds[n]);
+	free(leds);
+	return ret;
 }
 
 static struct of_device_id led_gpio_of_ids[] = {
-- 
2.1.0


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[PATCH v2 5/6] led: gpio: Free GPIOs on unregister()

[Sebastian Hesselbarth]

Free requested GPIOs on unregistration of mono-, bi-, and tri-color
GPIO leds.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
---
Changelog:
v1->v2:
- new patch

Cc: barebox@lists.infradead.org
---
 drivers/led/led-gpio.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/led/led-gpio.c b/drivers/led/led-gpio.c
index 807251721fd3..74be2304e868 100644
--- a/drivers/led/led-gpio.c
+++ b/drivers/led/led-gpio.c
@@ -64,6 +64,7 @@ int led_gpio_register(struct gpio_led *led)
 void led_gpio_unregister(struct gpio_led *led)
 {
 	led_unregister(&led->led);
+	gpio_free(led->gpio);
 }
 
 #ifdef CONFIG_LED_GPIO_BICOLOR
@@ -131,6 +132,8 @@ err_gpio_c0:
 void led_gpio_bicolor_unregister(struct gpio_bicolor_led *led)
 {
 	led_unregister(&led->led);
+	gpio_free(led->gpio_c1);
+	gpio_free(led->gpio_c0);
 }
 #endif
 
@@ -195,6 +198,9 @@ err_gpio_r:
 void led_gpio_rgb_unregister(struct gpio_led *led)
 {
 	led_unregister(&led->led);
+	gpio_free(led->gpio_b);
+	gpio_free(led->gpio_g);
+	gpio_free(led->gpio_r);
 }
 #endif /* CONFIG_LED_GPIO_RGB */
 
-- 
2.1.0


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[PATCH v2 6/6] gpio: orion: Convert to platform_driver

[Sebastian Hesselbarth]

With support for deferred probing, we can now relax driver
registration for Marvell Orion GPIO driver from postcore_initcall()
to normal platform_driver.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
---
Changelog:
v1->v2:
- new patch

Cc: barebox@lists.infradead.org
---
 drivers/gpio/gpio-orion.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/gpio/gpio-orion.c b/drivers/gpio/gpio-orion.c
index 855763ea665a..3deeac126f25 100644
--- a/drivers/gpio/gpio-orion.c
+++ b/drivers/gpio/gpio-orion.c
@@ -124,9 +124,4 @@ static struct driver_d orion_gpio_driver = {
 	.probe = orion_gpio_probe,
 	.of_compatible = DRV_OF_COMPAT(orion_gpio_dt_ids),
 };
-
-static int orion_gpio_init(void)
-{
-	return platform_driver_register(&orion_gpio_driver);
-}
-postcore_initcall(orion_gpio_init);
+device_platform_driver(orion_gpio_driver);
-- 
2.1.0


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Re: [PATCH v2 0/6] Introduce deferred probing

[Sascha Hauer]

On Wed, Apr 15, 2015 at 12:53:14AM +0200, Sebastian Hesselbarth wrote:
> This is round two of the introduction of deferred probing by moving
> drivers that request probe deferral to an extra device list that will
> be re-probed later.
> 
> Compared to v1 there are the following changes:
> - Loop over deferred device list until none succeeds
>   (Suggested by Sascha Hauer)
> - (Now) properly deal with deferred probing in led-gpio
> - Free GPIOs claimed by leds on foo_led_unregister()
> - Convert Orion GPIO to real platform driver
> Each patch also contains an individual changelog.
> 
> It would be great to give this patch series a little more coverage.
> Also, several other subsystems could use some support -EPROBE_DEFER
> but IMHO we should wait for someone to actually force probe deferral
> there.
> 
> Sebastian Hesselbarth (6):
>   base: Introduce deferred probing
>   gpio: Return -EPROBE_DEFER on gpio_get_num()
>   OF: gpio: Silence error message on -EPROBE_DEFER
>   led: gpio: Properly deal with deferred probing
>   led: gpio: Free GPIOs on unregister()
>   gpio: orion: Convert to platform_driver

Applied, thanks

Sascha


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