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>

1 files changed, 8 insertions, 7 deletions

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index d663338cb4a8..5203a599d211 100644
--- a/kernel/irq/chip.c
+++ b/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);