linux-kernel - [PATCH 2/2] g_NCR5380: Test the IRQ before accepting it

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Date:   Sun, 30 Oct 2016 11:49:43 +0100
From:   Ondrej Zary <linux@...nbow-software.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Finn Thain <fthain@...egraphics.com.au>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] g_NCR5380: Test the IRQ before accepting it

Trigger an IRQ first with a test IRQ handler to find out if it really
works. Disable the IRQ if not.
This prevents hang when incorrect IRQ was specified by user.

Signed-off-by: Ondrej Zary <linux@...nbow-software.org>
---
 drivers/scsi/g_NCR5380.c |   31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/g_NCR5380.c b/drivers/scsi/g_NCR5380.c
index 3790ed5..f0c5b10 100644
--- a/drivers/scsi/g_NCR5380.c
+++ b/drivers/scsi/g_NCR5380.c
@@ -67,6 +67,14 @@
 MODULE_ALIAS("g_NCR5380_mmio");
 MODULE_LICENSE("GPL");
 
+static bool irq_working;
+
+static irqreturn_t test_irq(int irq, void *dev_id)
+{
+	irq_working = true;
+	return IRQ_HANDLED;
+}
+
 /*
  * Configure I/O address of 53C400A or DTC436 by writing magic numbers
  * to ports 0x779 and 0x379.
@@ -275,10 +283,29 @@ static int generic_NCR5380_init_one(struct scsi_host_template *tpnt,
 		/* set IRQ for HP C2502 */
 		if (board == BOARD_HP_C2502)
 			magic_configure(port_idx, instance->irq, magic);
-		if (request_irq(instance->irq, generic_NCR5380_intr,
-				0, "NCR5380", instance)) {
+		/* test if the IRQ is working */
+		irq_working = false;
+		if (request_irq(instance->irq, test_irq,
+				0, "NCR5380-irqtest", NULL)) {
 			printk(KERN_WARNING "scsi%d : IRQ%d not free, interrupts disabled\n", instance->host_no, instance->irq);
 			instance->irq = NO_IRQ;
+		} else {
+			NCR5380_trigger_irq(instance);
+			free_irq(instance->irq, NULL);
+			if (irq_working) {
+				if (request_irq(instance->irq,
+						generic_NCR5380_intr, 0,
+						"NCR5380", instance)) {
+					printk(KERN_WARNING "scsi%d : IRQ%d not free, interrupts disabled\n",
+					       instance->host_no,
+					       instance->irq);
+					instance->irq = NO_IRQ;
+				}
+			} else {
+				printk(KERN_WARNING "scsi%d : IRQ%d not working, interrupts disabled\n",
+				       instance->host_no, instance->irq);
+				instance->irq = NO_IRQ;
+			}
 		}
 	}
 
-- 
Ondrej Zary