gpio: sim: lock simulated GPIOs as interrupts

From: Bartosz Golaszewski <[email protected]>

I realized that the gpio-sim module doesn't lock the GPIOs as interrupts when they are requested from the irq_sim. This leads to users being able to change the direction of GPIOs that should remain as inputs to output. This series adds a notifier to the interrupt simulator that users can register with to be informed about interrupts being requested and released so that they can act accordingly. The gpio-sim is made to use this notifier and lock GPIOs as interrupts when needed.

Thomas: if this is fine with you, can you Ack it so that I can take it through the GPIO tree for the next merge window?

Bartosz Golaszewski (2):
genirq/irq_sim: add a notifier for irqchip events
gpio: sim: lock GPIOs as interrupts when they are requested

 drivers/gpio/gpio-sim.c | 30 +++++++++++++++++--
 include/linux/irq_sim.h | 11 +++++++
 kernel/irq/irq_sim.c    | 64 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 103 insertions(+), 2 deletions(-)

2.40.1

From: Bartosz Golaszewski <[email protected]>

Currently users of the interrupt simulator don't have any way of being notified about interrupts from the simulated domain being requested or released. This causes a problem for one of the users - the GPIO simulator - which is unable to lock the pins as interrupts.

Add a blocking notifier and provide interfaces to register with it, then use it to notify users of the domain about interrupts being requested and released while also leaving space for future extensions.

---
 include/linux/irq_sim.h | 11 +++++++
 kernel/irq/irq_sim.c    | 64 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+)

index ab831e5ae748..462d1913bb27 100644
@@ -10,6 +10,7 @@
 #include <linux/device.h>
 #include <linux/fwnode.h>
 #include <linux/irqdomain.h>
+#include <linux/notifier.h>
 
 /*
  * Provides a framework for allocating simulated interrupts which can be

@@ -23,4 +24,14 @@ struct irq_domain *devm_irq_domain_create_sim(struct device *dev,
 					      unsigned int num_irqs);
 void irq_domain_remove_sim(struct irq_domain *domain);
 
+enum {
+	IRQ_SIM_DOMAIN_IRQ_REQUESTED = 1,
+	IRQ_SIM_DOMAIN_IRQ_RELEASED,
+};
+
+int irq_sim_domain_register_notifier(struct irq_domain *domain,
+				     struct notifier_block *nb);
+int irq_sim_domain_unregister_notifier(struct irq_domain *domain,
+				       struct notifier_block *nb);
+
 #endif /* _LINUX_IRQ_SIM_H */

2.40.1

Why a notifier?

There is only one usage site per simulator domain. So there is no reason to have a notifier with handwaving about future extensions.

The right thing to do is:

typedef void (*irq_sim_cb_t)(irq_hw_number_t hwirq, bool request, void *data)

struct irq_domain *irq_domain_create_sim(struct fwnode_handle *fwnode,

					 unsigned int num_irqs,
                                         irq_sim_cb_t *cb, void *cb_data);

You get the idea, right?

Thanks,

tglx

If you're opposed to the notifier, can we at least make it somewhat future-proof and more elegant with the following?

struct irq_sim_ops {
	int (*irq_sim_irq_requested)(irq_hw_number_t hwirq , void *data);
	int (*irq_sim_irq_released)(irq_hw_number_t hwirq, void *data);
};

struct irq_domain *irq_domain_create_sim_ext(struct fwnode_handle *fwnode,
unsigned int num_irqs, const struct irq_sim_ops *ops, void *data);

This way we don't have to change the other call-site over at IIO at all nor will need to change the prototype for irq_domain_create_sim_ext() if another callback is needed.

Bart

release wants to be void.

I'm fine with that. It's at least well defined, while the notifier business is not :)

Thanks,

tglx

From: Bartosz Golaszewski <[email protected]>

Use the notifier exposed by the interrupt simulator to be notified about interrupts associated with simulated GPIO pins being requested or released and lock/unlock them as interrupts accordingly.

---
 drivers/gpio/gpio-sim.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

index 2ed5cbe7c8a8..b5526f09b22b 100644
@@ -53,6 +53,7 @@ struct gpio_sim_chip {
 	struct irq_domain *irq_sim;
 	struct mutex lock;
 	const struct attribute_group **attr_groups;
+	struct notifier_block nb;
 };
 
 struct gpio_sim_attribute {

@@ -227,6 +228,24 @@ static void gpio_sim_free(struct gpio_chip *gc, unsigned int offset)
 	}
 }
 
+static int gpio_sim_irq_domain_notify(struct notifier_block *nb,
+				      unsigned long action, void *data)
+{
+	struct gpio_sim_chip *chip = container_of(nb, struct gpio_sim_chip, nb);
+	irq_hw_number_t *offset = data;
+
+	switch (action) {
+	case IRQ_SIM_DOMAIN_IRQ_REQUESTED:
+		gpiochip_lock_as_irq(&chip->gc, *offset);
+		return NOTIFY_OK;
+	case IRQ_SIM_DOMAIN_IRQ_RELEASED:
+		gpiochip_unlock_as_irq(&chip->gc, *offset);
+		return NOTIFY_OK;
+	}
+
+	return NOTIFY_DONE;
+}
+
 static void gpio_sim_dbg_show(struct seq_file *seq, struct gpio_chip *gc)
 {
 	struct gpio_sim_chip *chip = gpiochip_get_data(gc);

@@ -322,13 +341,15 @@ static void gpio_sim_put_device(void *data)
 	put_device(dev);
 }
 
-static void gpio_sim_dispose_mappings(void *data)
+static void gpio_sim_teardown_irq_sim(void *data)
 {
 	struct gpio_sim_chip *chip = data;
 	unsigned int i;
 
 	for (i = 0; i < chip->gc.ngpio; i++)
 		irq_dispose_mapping(irq_find_mapping(chip->irq_sim, i));
+
+	irq_sim_domain_unregister_notifier(chip->irq_sim, &chip->nb);
 }
 
 static void gpio_sim_sysfs_remove(void *data)

@@ -454,7 +475,12 @@ static int gpio_sim_add_bank(struct fwnode_handle *swnode, struct device *dev)
 	if (IS_ERR(chip->irq_sim))
 		return PTR_ERR(chip->irq_sim);
 
-	ret = devm_add_action_or_reset(dev, gpio_sim_dispose_mappings, chip);
+	chip->nb.notifier_call = gpio_sim_irq_domain_notify;
+	ret = irq_sim_domain_register_notifier(chip->irq_sim, &chip->nb);
+	if (ret)
+		return ret;
+
+	ret = devm_add_action_or_reset(dev, gpio_sim_teardown_irq_sim, chip);
 	if (ret)
 		return ret;
 

2.40.1