genirq: record trigger type

Genirq hasn't previously recorded the trigger type used by any given IRQ,
although some irq_chip support has done so.  That data can be useful when
troubleshooting.  This patch records it in the relevant irq_desc.status
bits, and improves consistency between the two driver-visible calls
affected:

 - Make set_irq_type() usage match request_irq() usage:
    * IRQ_TYPE_NONE should be a NOP; succeed, so irq_chip methods
      won't have to handle that case any more (many do it wrong).
    * IRQ_TYPE_PROBE is ignored; any buggy out-of-tree callers
      might need to switch over to the real IRQ probing code.
    * emit the same diagnostics (from shared utility code)

 - Their kerneldoc now reflects usage:
    * request_irq() flags include IRQF_TRIGGER_* to specify
      active edge(s)/level ... docs previously omitted that
    * set_irq_type() is declared in <linux/irq.h> so callers
      should use the (bit-equivalent) IRQ_TYPE_* symbols there

Also: adds a warning about shared IRQs that don't end up using the
requested trigger mode; and fix an unrelated "sparse" warning.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/irq/chip.c

@@ -111,9 +111,9 @@ int set_irq_chip(unsigned int irq, struct irq_chip *chip)
 EXPORT_SYMBOL(set_irq_chip);
 
 /**
- *	set_irq_type - set the irq type for an irq
+ *	set_irq_type - set the irq trigger type for an irq
  *	@irq:	irq number
- *	@type:	interrupt type - see include/linux/interrupt.h
+ *	@type:	IRQ_TYPE_{LEVEL,EDGE}_* value - see include/linux/irq.h
  */
 int set_irq_type(unsigned int irq, unsigned int type)
 {
@@ -127,11 +127,12 @@ int set_irq_type(unsigned int irq, unsigned int type)
 	}
 
 	desc = irq_desc + irq;
-	if (desc->chip->set_type) {
-		spin_lock_irqsave(&desc->lock, flags);
-		ret = desc->chip->set_type(irq, type);
-		spin_unlock_irqrestore(&desc->lock, flags);
-	}
+	if (type == IRQ_TYPE_NONE)
+		return 0;
+
+	spin_lock_irqsave(&desc->lock, flags);
+	ret = __irq_set_trigger(desc, irq, flags);
+	spin_unlock_irqrestore(&desc->lock, flags);
 	return ret;
 }
 EXPORT_SYMBOL(set_irq_type);

kernel/irq/internals.h

@@ -10,6 +10,9 @@ extern void irq_chip_set_defaults(struct irq_chip *chip);
 /* Set default handler: */
 extern void compat_irq_chip_set_default_handler(struct irq_desc *desc);
 
+extern int __irq_set_trigger(struct irq_desc *desc, unsigned int irq,
+		unsigned long flags);
+
 #ifdef CONFIG_PROC_FS
 extern void register_irq_proc(unsigned int irq);
 extern void register_handler_proc(unsigned int irq, struct irqaction *action);

kernel/irq/manage.c

@@ -216,7 +216,7 @@ void enable_irq(unsigned int irq)
 }
 EXPORT_SYMBOL(enable_irq);
 
-int set_irq_wake_real(unsigned int irq, unsigned int on)
+static int set_irq_wake_real(unsigned int irq, unsigned int on)
 {
 	struct irq_desc *desc = irq_desc + irq;
 	int ret = -ENXIO;
@@ -305,10 +305,11 @@ void compat_irq_chip_set_default_handler(struct irq_desc *desc)
 		desc->handle_irq = NULL;
 }
 
-static int __irq_set_trigger(struct irq_chip *chip, unsigned int irq,
+int __irq_set_trigger(struct irq_desc *desc, unsigned int irq,
 		unsigned long flags)
 {
 	int ret;
+	struct irq_chip *chip = desc->chip;
 
 	if (!chip || !chip->set_type) {
 		/*
@@ -326,6 +327,11 @@ static int __irq_set_trigger(struct irq_chip *chip, unsigned int irq,
 		pr_err("setting trigger mode %d for irq %u failed (%pF)\n",
 				(int)(flags & IRQF_TRIGGER_MASK),
 				irq, chip->set_type);
+	else {
+		/* note that IRQF_TRIGGER_MASK == IRQ_TYPE_SENSE_MASK */
+		desc->status &= ~IRQ_TYPE_SENSE_MASK;
+		desc->status |= flags & IRQ_TYPE_SENSE_MASK;
+	}
 
 	return ret;
 }
@@ -404,7 +410,7 @@ int setup_irq(unsigned int irq, struct irqaction *new)
 
 		/* Setup the type (level, edge polarity) if configured: */
 		if (new->flags & IRQF_TRIGGER_MASK) {
-			ret = __irq_set_trigger(desc->chip, irq, new->flags);
+			ret = __irq_set_trigger(desc, irq, new->flags);
 
 			if (ret) {
 				spin_unlock_irqrestore(&desc->lock, flags);
@@ -430,6 +436,14 @@ int setup_irq(unsigned int irq, struct irqaction *new)
 
 		/* Set default affinity mask once everything is setup */
 		irq_select_affinity(irq);
+
+	} else if ((new->flags & IRQF_TRIGGER_MASK)
+			&& (new->flags & IRQF_TRIGGER_MASK)
+				!= (desc->status & IRQ_TYPE_SENSE_MASK)) {
+		/* hope the handler works with the actual trigger mode... */
+		pr_warning("IRQ %d uses trigger mode %d; requested %d\n",
+				irq, (int)(desc->status & IRQ_TYPE_SENSE_MASK),
+				(int)(new->flags & IRQF_TRIGGER_MASK));
 	}
 
 	*p = new;
@@ -586,6 +600,7 @@ EXPORT_SYMBOL(free_irq);
  *	IRQF_SHARED		Interrupt is shared
  *	IRQF_DISABLED	Disable local interrupts while processing
  *	IRQF_SAMPLE_RANDOM	The interrupt can be used for entropy
+ *	IRQF_TRIGGER_*		Specify active edge(s) or level
  *
  */
 int request_irq(unsigned int irq, irq_handler_t handler,