[PATCH 0/2] leds: gpio: Add devlink between the leds-gpio device and the gpio used.

[PATCH 0/2] leds: gpio: Add devlink between the leds-gpio device and the gpio used.

[Herve Codina]

Hi,

When a gpio used by the leds-gpio device is removed, the leds-gpio
device continues to use this gpio. Also, when the gpio is back, the
leds-gpio still uses the old removed gpio.

A consumer/supplier relationship is missing between the leds-gpio device
(consumer) and the gpio used (supplier).

This series adds an addionnal devlink between this two device.
With this link when the gpio is removed, the leds-gpio device is also
removed.

Best regards,
Hervé Codina

Herve Codina (2):
  gpiolib: Introduce gpiod_device_add_link()
  leds: gpio: Add devlinks between the gpio consumed and the gpio leds
    device

 drivers/gpio/gpiolib.c        | 32 ++++++++++++++++++++++++++++++++
 drivers/leds/leds-gpio.c      | 15 +++++++++++++++
 include/linux/gpio/consumer.h |  5 +++++
 3 files changed, 52 insertions(+)

-- 
2.43.0

[PATCH 1/2] gpiolib: Introduce gpiod_device_add_link()

[Herve Codina]

With device-tree, some devlink related to gpios are automatically added
when a consumer device is added and the attached node has phandles
related to GPIOs.
In some cases, the real device used to get the gpio during a probe() can
be related to an of-node parent of the of-node used for the already done
automatically devlink creation.
For instance, a driver can be bound to a device and, during the
probe(), the driver can walk its of-node children to get the GPIO
described in these children nodes.
In that case, an additional devlink between the device attached to the
driver and the gpio consumer need to be created.
Indeed, if the GPIO is removed, the consumer/supplier dependency should
lead to remove first the consuming driver before removing the supplier.

In order to give the possibility to this kind of driver to add additional
devlinks, introduce gpiod_device_add_link().

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/gpio/gpiolib.c        | 32 ++++++++++++++++++++++++++++++++
 include/linux/gpio/consumer.h |  5 +++++
 2 files changed, 37 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 8b3a0f45b574..416ab334b02d 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -4195,6 +4195,38 @@ static struct gpio_desc *gpiod_find_and_request(struct device *consumer,
 	return desc;
 }
 
+/**
+ * gpiod_device_add_link - Add a link between a GPIO consumer and a GPIO.
+ * @consumer: GPIO consumer.
+ * @desc: GPIO consumed.
+ * @flags: Link flags, see device_link_add().
+ *
+ * This function can be used for drivers that need to add an additional
+ * consumer/supplier device link to a GPIO.
+ *
+ * Returns:
+ * On successful, the link created.
+ * NULL if the link was not created due to a missing GPIO parent.
+ *
+ * In case of error an ERR_PTR() is returned.
+ */
+struct device_link *gpiod_device_add_link(struct device *consumer,
+					  struct gpio_desc *desc,
+					  u32 flags)
+{
+	struct device_link *link;
+
+	if (!desc->gdev->dev.parent)
+		return NULL;
+
+	link = device_link_add(consumer, desc->gdev->dev.parent, flags);
+	if (!link)
+		return ERR_PTR(-EINVAL);
+
+	return link;
+}
+EXPORT_SYMBOL_GPL(gpiod_device_add_link);
+
 /**
  * fwnode_gpiod_get_index - obtain a GPIO from firmware node
  * @fwnode:	handle of the firmware node
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index db2dfbae8edb..4feed4e166b0 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -7,6 +7,7 @@
 
 struct acpi_device;
 struct device;
+struct device_link;
 struct fwnode_handle;
 
 struct gpio_array;
@@ -106,6 +107,10 @@ void devm_gpiod_put(struct device *dev, struct gpio_desc *desc);
 void devm_gpiod_unhinge(struct device *dev, struct gpio_desc *desc);
 void devm_gpiod_put_array(struct device *dev, struct gpio_descs *descs);
 
+struct device_link *gpiod_device_add_link(struct device *consumer,
+					  struct gpio_desc *desc,
+					  u32 flags);
+
 int gpiod_get_direction(struct gpio_desc *desc);
 int gpiod_direction_input(struct gpio_desc *desc);
 int gpiod_direction_output(struct gpio_desc *desc, int value);
-- 
2.43.0

Re: [PATCH 1/2] gpiolib: Introduce gpiod_device_add_link()

[Linus Walleij]

Looping in Saravana, he should always look at patches like this.

On Tue, Feb 20, 2024 at 12:11 PM Herve Codina <herve.codina@bootlin.com> wrote:
>
> With device-tree, some devlink related to gpios are automatically added
> when a consumer device is added and the attached node has phandles
> related to GPIOs.
> In some cases, the real device used to get the gpio during a probe() can
> be related to an of-node parent of the of-node used for the already done
> automatically devlink creation.
> For instance, a driver can be bound to a device and, during the
> probe(), the driver can walk its of-node children to get the GPIO
> described in these children nodes.
> In that case, an additional devlink between the device attached to the
> driver and the gpio consumer need to be created.
> Indeed, if the GPIO is removed, the consumer/supplier dependency should
> lead to remove first the consuming driver before removing the supplier.
>
> In order to give the possibility to this kind of driver to add additional
> devlinks, introduce gpiod_device_add_link().
>
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>
> ---
>  drivers/gpio/gpiolib.c        | 32 ++++++++++++++++++++++++++++++++
>  include/linux/gpio/consumer.h |  5 +++++
>  2 files changed, 37 insertions(+)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 8b3a0f45b574..416ab334b02d 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -4195,6 +4195,38 @@ static struct gpio_desc *gpiod_find_and_request(struct device *consumer,
>         return desc;
>  }
>
> +/**
> + * gpiod_device_add_link - Add a link between a GPIO consumer and a GPIO.
> + * @consumer: GPIO consumer.
> + * @desc: GPIO consumed.
> + * @flags: Link flags, see device_link_add().
> + *
> + * This function can be used for drivers that need to add an additional
> + * consumer/supplier device link to a GPIO.
> + *
> + * Returns:
> + * On successful, the link created.
> + * NULL if the link was not created due to a missing GPIO parent.
> + *
> + * In case of error an ERR_PTR() is returned.
> + */
> +struct device_link *gpiod_device_add_link(struct device *consumer,
> +                                         struct gpio_desc *desc,
> +                                         u32 flags)
> +{
> +       struct device_link *link;
> +
> +       if (!desc->gdev->dev.parent)
> +               return NULL;
> +
> +       link = device_link_add(consumer, desc->gdev->dev.parent, flags);
> +       if (!link)
> +               return ERR_PTR(-EINVAL);
> +
> +       return link;
> +}
> +EXPORT_SYMBOL_GPL(gpiod_device_add_link);
> +
>  /**
>   * fwnode_gpiod_get_index - obtain a GPIO from firmware node
>   * @fwnode:    handle of the firmware node
> diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
> index db2dfbae8edb..4feed4e166b0 100644
> --- a/include/linux/gpio/consumer.h
> +++ b/include/linux/gpio/consumer.h
> @@ -7,6 +7,7 @@
>
>  struct acpi_device;
>  struct device;
> +struct device_link;
>  struct fwnode_handle;
>
>  struct gpio_array;
> @@ -106,6 +107,10 @@ void devm_gpiod_put(struct device *dev, struct gpio_desc *desc);
>  void devm_gpiod_unhinge(struct device *dev, struct gpio_desc *desc);
>  void devm_gpiod_put_array(struct device *dev, struct gpio_descs *descs);
>
> +struct device_link *gpiod_device_add_link(struct device *consumer,
> +                                         struct gpio_desc *desc,
> +                                         u32 flags);
> +
>  int gpiod_get_direction(struct gpio_desc *desc);
>  int gpiod_direction_input(struct gpio_desc *desc);
>  int gpiod_direction_output(struct gpio_desc *desc, int value);

The function as such is pretty straight forward, but the cross call
here happens on instatiated
devices etc, and we need to know why this can't be done earlier when sorting out
the dependencies in the device tree e.g.

Yours,
Linus Walleij

Re: [PATCH 1/2] gpiolib: Introduce gpiod_device_add_link()

[Saravana Kannan]

On Wed, Feb 21, 2024 at 2:44 PM Linus Walleij <linus.walleij@linaro.org> wrote:
>
> Looping in Saravana, he should always look at patches like this.

Thanks Linus. Bartosz suggested a RESEND with me and I replied in that thread.

https://lore.kernel.org/all/20240220133950.138452-1-herve.codina@bootlin.com/

-Saravana
>
> On Tue, Feb 20, 2024 at 12:11 PM Herve Codina <herve.codina@bootlin.com> wrote:
> >
> > With device-tree, some devlink related to gpios are automatically added
> > when a consumer device is added and the attached node has phandles
> > related to GPIOs.
> > In some cases, the real device used to get the gpio during a probe() can
> > be related to an of-node parent of the of-node used for the already done
> > automatically devlink creation.
> > For instance, a driver can be bound to a device and, during the
> > probe(), the driver can walk its of-node children to get the GPIO
> > described in these children nodes.
> > In that case, an additional devlink between the device attached to the
> > driver and the gpio consumer need to be created.
> > Indeed, if the GPIO is removed, the consumer/supplier dependency should
> > lead to remove first the consuming driver before removing the supplier.
> >
> > In order to give the possibility to this kind of driver to add additional
> > devlinks, introduce gpiod_device_add_link().
> >
> > Signed-off-by: Herve Codina <herve.codina@bootlin.com>
> > ---
> >  drivers/gpio/gpiolib.c        | 32 ++++++++++++++++++++++++++++++++
> >  include/linux/gpio/consumer.h |  5 +++++
> >  2 files changed, 37 insertions(+)
> >
> > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > index 8b3a0f45b574..416ab334b02d 100644
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -4195,6 +4195,38 @@ static struct gpio_desc *gpiod_find_and_request(struct device *consumer,
> >         return desc;
> >  }
> >
> > +/**
> > + * gpiod_device_add_link - Add a link between a GPIO consumer and a GPIO.
> > + * @consumer: GPIO consumer.
> > + * @desc: GPIO consumed.
> > + * @flags: Link flags, see device_link_add().
> > + *
> > + * This function can be used for drivers that need to add an additional
> > + * consumer/supplier device link to a GPIO.
> > + *
> > + * Returns:
> > + * On successful, the link created.
> > + * NULL if the link was not created due to a missing GPIO parent.
> > + *
> > + * In case of error an ERR_PTR() is returned.
> > + */
> > +struct device_link *gpiod_device_add_link(struct device *consumer,
> > +                                         struct gpio_desc *desc,
> > +                                         u32 flags)
> > +{
> > +       struct device_link *link;
> > +
> > +       if (!desc->gdev->dev.parent)
> > +               return NULL;
> > +
> > +       link = device_link_add(consumer, desc->gdev->dev.parent, flags);
> > +       if (!link)
> > +               return ERR_PTR(-EINVAL);
> > +
> > +       return link;
> > +}
> > +EXPORT_SYMBOL_GPL(gpiod_device_add_link);
> > +
> >  /**
> >   * fwnode_gpiod_get_index - obtain a GPIO from firmware node
> >   * @fwnode:    handle of the firmware node
> > diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
> > index db2dfbae8edb..4feed4e166b0 100644
> > --- a/include/linux/gpio/consumer.h
> > +++ b/include/linux/gpio/consumer.h
> > @@ -7,6 +7,7 @@
> >
> >  struct acpi_device;
> >  struct device;
> > +struct device_link;
> >  struct fwnode_handle;
> >
> >  struct gpio_array;
> > @@ -106,6 +107,10 @@ void devm_gpiod_put(struct device *dev, struct gpio_desc *desc);
> >  void devm_gpiod_unhinge(struct device *dev, struct gpio_desc *desc);
> >  void devm_gpiod_put_array(struct device *dev, struct gpio_descs *descs);
> >
> > +struct device_link *gpiod_device_add_link(struct device *consumer,
> > +                                         struct gpio_desc *desc,
> > +                                         u32 flags);
> > +
> >  int gpiod_get_direction(struct gpio_desc *desc);
> >  int gpiod_direction_input(struct gpio_desc *desc);
> >  int gpiod_direction_output(struct gpio_desc *desc, int value);
>
> The function as such is pretty straight forward, but the cross call
> here happens on instatiated
> devices etc, and we need to know why this can't be done earlier when sorting out
> the dependencies in the device tree e.g.
>
> Yours,
> Linus Walleij

[PATCH 2/2] leds: gpio: Add devlinks between the gpio consumed and the gpio leds device

[Herve Codina]

When a gpio is removed, the gpio leds consumer need to be removed first.
This dependency consumer/supplier can be described by devlink links.
In case of device-tree, even if some devlinks are created due to the
presence of gpio phandles in the gpio leds children, these links do not
help in removing the gpio leds device (i.e. the real consumer) before
the consumed gpio.
We can reach cases where the gpio are no more present and the gpio leds
driver continue to have leds using these gpio.
Further more, when the gpio come back, the gpio leds still use the old
removed one.

Indeed, the gpio are consumed by the parent of the consumer used in the
devlink creation due to phandles. A link is missing between the gpio and
the real gpio consumer, the gpio leds device itself.

Use the newly introduced gpiod_device_add_link() to create this
missing link between the gpio leds devices and the gpios.
With that done, if a gpio is removed, the gpio leds is removed and the
resources are correctly released.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/leds/leds-gpio.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/leds/leds-gpio.c b/drivers/leds/leds-gpio.c
index 83fcd7b6afff..b3ec8ecbe5da 100644
--- a/drivers/leds/leds-gpio.c
+++ b/drivers/leds/leds-gpio.c
@@ -150,6 +150,7 @@ static struct gpio_leds_priv *gpio_leds_create(struct device *dev)
 {
 	struct fwnode_handle *child;
 	struct gpio_leds_priv *priv;
+	struct device_link *link;
 	int count, ret;
 
 	count = device_get_child_node_count(dev);
@@ -197,6 +198,20 @@ static struct gpio_leds_priv *gpio_leds_create(struct device *dev)
 		/* Set gpiod label to match the corresponding LED name. */
 		gpiod_set_consumer_name(led_dat->gpiod,
 					led_dat->cdev.dev->kobj.name);
+
+		/*
+		 * Create a link between the GPIO and the gpio-leds device.
+		 * This allow to have a relationship between the gpio used and
+		 * the gpio-leds device in order to automatically remove the
+		 * gpio-leds device (consumer) when a GPIO (supplier) is removed.
+		 */
+		link = gpiod_device_add_link(dev, led_dat->gpiod,
+					     DL_FLAG_AUTOREMOVE_CONSUMER);
+		if (IS_ERR(link)) {
+			fwnode_handle_put(child);
+			return ERR_CAST(link);
+		}
+
 		priv->num_leds++;
 	}
 
-- 
2.43.0

Re: [PATCH 2/2] leds: gpio: Add devlinks between the gpio consumed and the gpio leds device

[Linus Walleij]

Saravana needs to look at this patch too, so I am top-posting.

Yours,
Linus Walleij

On Tue, Feb 20, 2024 at 12:11 PM Herve Codina <herve.codina@bootlin.com> wrote:

> When a gpio is removed, the gpio leds consumer need to be removed first.
> This dependency consumer/supplier can be described by devlink links.
> In case of device-tree, even if some devlinks are created due to the
> presence of gpio phandles in the gpio leds children, these links do not
> help in removing the gpio leds device (i.e. the real consumer) before
> the consumed gpio.
> We can reach cases where the gpio are no more present and the gpio leds
> driver continue to have leds using these gpio.
> Further more, when the gpio come back, the gpio leds still use the old
> removed one.
>
> Indeed, the gpio are consumed by the parent of the consumer used in the
> devlink creation due to phandles. A link is missing between the gpio and
> the real gpio consumer, the gpio leds device itself.
>
> Use the newly introduced gpiod_device_add_link() to create this
> missing link between the gpio leds devices and the gpios.
> With that done, if a gpio is removed, the gpio leds is removed and the
> resources are correctly released.
>
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>
> ---
>  drivers/leds/leds-gpio.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/drivers/leds/leds-gpio.c b/drivers/leds/leds-gpio.c
> index 83fcd7b6afff..b3ec8ecbe5da 100644
> --- a/drivers/leds/leds-gpio.c
> +++ b/drivers/leds/leds-gpio.c
> @@ -150,6 +150,7 @@ static struct gpio_leds_priv *gpio_leds_create(struct device *dev)
>  {
>         struct fwnode_handle *child;
>         struct gpio_leds_priv *priv;
> +       struct device_link *link;
>         int count, ret;
>
>         count = device_get_child_node_count(dev);
> @@ -197,6 +198,20 @@ static struct gpio_leds_priv *gpio_leds_create(struct device *dev)
>                 /* Set gpiod label to match the corresponding LED name. */
>                 gpiod_set_consumer_name(led_dat->gpiod,
>                                         led_dat->cdev.dev->kobj.name);
> +
> +               /*
> +                * Create a link between the GPIO and the gpio-leds device.
> +                * This allow to have a relationship between the gpio used and
> +                * the gpio-leds device in order to automatically remove the
> +                * gpio-leds device (consumer) when a GPIO (supplier) is removed.
> +                */
> +               link = gpiod_device_add_link(dev, led_dat->gpiod,
> +                                            DL_FLAG_AUTOREMOVE_CONSUMER);
> +               if (IS_ERR(link)) {
> +                       fwnode_handle_put(child);
> +                       return ERR_CAST(link);
> +               }
> +
>                 priv->num_leds++;
>         }
>
> --
> 2.43.0
>

Re: [PATCH 0/2] leds: gpio: Add devlink between the leds-gpio device and the gpio used.

[Bartosz Golaszewski]

On Tue, Feb 20, 2024 at 12:11 PM Herve Codina <herve.codina@bootlin.com> wrote:
>
> Hi,
>
> When a gpio used by the leds-gpio device is removed, the leds-gpio
> device continues to use this gpio. Also, when the gpio is back, the
> leds-gpio still uses the old removed gpio.
>
> A consumer/supplier relationship is missing between the leds-gpio device
> (consumer) and the gpio used (supplier).
>
> This series adds an addionnal devlink between this two device.
> With this link when the gpio is removed, the leds-gpio device is also
> removed.
>
> Best regards,
> Hervé Codina
>
> Herve Codina (2):
>   gpiolib: Introduce gpiod_device_add_link()
>   leds: gpio: Add devlinks between the gpio consumed and the gpio leds
>     device
>
>  drivers/gpio/gpiolib.c        | 32 ++++++++++++++++++++++++++++++++
>  drivers/leds/leds-gpio.c      | 15 +++++++++++++++
>  include/linux/gpio/consumer.h |  5 +++++
>  3 files changed, 52 insertions(+)
>
> --
> 2.43.0
>

You should probably Cc Saravana on anything devlink related.

Bart

Re: [PATCH 0/2] leds: gpio: Add devlink between the leds-gpio device and the gpio used.

[Herve Codina]

Hi Bartosz,

On Tue, 20 Feb 2024 12:40:17 +0100
Bartosz Golaszewski <brgl@bgdev.pl> wrote:

> On Tue, Feb 20, 2024 at 12:11 PM Herve Codina <herve.codina@bootlin.com> wrote:
> >
> > Hi,
> >
> > When a gpio used by the leds-gpio device is removed, the leds-gpio
> > device continues to use this gpio. Also, when the gpio is back, the
> > leds-gpio still uses the old removed gpio.
> >
> > A consumer/supplier relationship is missing between the leds-gpio device
> > (consumer) and the gpio used (supplier).
> >
> > This series adds an addionnal devlink between this two device.
> > With this link when the gpio is removed, the leds-gpio device is also
> > removed.
> >
> > Best regards,
> > Hervé Codina
> >
> > Herve Codina (2):
> >   gpiolib: Introduce gpiod_device_add_link()
> >   leds: gpio: Add devlinks between the gpio consumed and the gpio leds
> >     device
> >
> >  drivers/gpio/gpiolib.c        | 32 ++++++++++++++++++++++++++++++++
> >  drivers/leds/leds-gpio.c      | 15 +++++++++++++++
> >  include/linux/gpio/consumer.h |  5 +++++
> >  3 files changed, 52 insertions(+)
> >
> > --
> > 2.43.0
> >  
> 
> You should probably Cc Saravana on anything devlink related.
> 

Sure, I am going to resend the whole series adding Saravana.

Regards,
Hervé