linux-kernel - [PATCH] fix return value of i8042_aux_test

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Date:	Thu, 26 Jul 2007 17:04:25 +0900
From:	Fernando Luis Vázquez Cao 
	<fernando@....ntt.co.jp>
To:	linux-kernel@...r.kernel.org
Cc:	dmitry.torokhov@...il.com, dtor@...l.ru, vojtech@...e.cz,
	akpm@...ux-foundation.org
Subject: [PATCH] fix return value of i8042_aux_test_irq

I made an interesting finding while testing the two patches below.

http://lkml.org/lkml/2007/7/19/685
http://lkml.org/lkml/2007/7/19/687

These patches modify the traditional CONFIG_DEBUG_KERNEL in such a way
that the request_irq prints a warning if after calling the handler it
returned IRQ_HANDLED .

The code looks like this:

int request_irq(unsigned int irq, irq_handler_t handler,
                unsigned long irqflags, const char *devname, void
*dev_id)
.....
        if (irqflags & IRQF_DISABLED) {
                unsigned long flags;

                local_irq_save(flags);
                retval = handler(irq, dev_id);
                local_irq_restore(flags);
        } else
                retval = handler(irq, dev_id);
        if (retval == IRQ_HANDLED) {
                printk(KERN_WARNING
                       "%s (IRQ %d) handled a spurious interrupt\n",
                       devname, irq);
        }
.....

I discovered that i8042_aux_test_irq handles the "fake" interrupt,
which, in principle, is not correct because it obviously isn't a real
interrupt and it could have been a spurious interrupt as well.

The problem is that the interrupt handler unconditionally returns IRQ
handled, which does not seem correct. Anyway I am not very familiar with
this code so I may be missing the whole point. I would appreciate your
comments on this.

Thank you in advance.

Fernando

--

Do not return IRQ_HANDLED when we haven't handle the interrupt.

Signed-off-by: Fernando Luis Vazquez Cao <fernando@....ntt.co.jp>
---

diff -urNp linux-2.6.23-rc1-mm1-orig/drivers/input/serio/i8042.c linux-2.6.23-rc1-mm1/drivers/input/serio/i8042.c
--- linux-2.6.23-rc1-mm1-orig/drivers/input/serio/i8042.c	2007-07-26 16:10:11.000000000 +0900
+++ linux-2.6.23-rc1-mm1/drivers/input/serio/i8042.c	2007-07-26 16:05:19.000000000 +0900
@@ -516,6 +516,7 @@ static irqreturn_t __devinit i8042_aux_t
 {
 	unsigned long flags;
 	unsigned char str, data;
+	int ret;
 
 	spin_lock_irqsave(&i8042_lock, flags);
 	str = i8042_read_status();
@@ -524,10 +525,13 @@ static irqreturn_t __devinit i8042_aux_t
 		if (i8042_irq_being_tested &&
 		    data == 0xa5 && (str & I8042_STR_AUXDATA))
 			complete(&i8042_aux_irq_delivered);
+		ret = 1;
 	}
+	else
+		ret = 0;
 	spin_unlock_irqrestore(&i8042_lock, flags);
 
-	return IRQ_HANDLED;
+	return IRQ_RETVAL(ret);
 }
 
 /*


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