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Diffstat (limited to 'arch/x86/kernel/i8259.c')
-rw-r--r--arch/x86/kernel/i8259.c20
1 files changed, 19 insertions, 1 deletions
diff --git a/arch/x86/kernel/i8259.c b/arch/x86/kernel/i8259.c
index 2e977b5d61d..8af817105e2 100644
--- a/arch/x86/kernel/i8259.c
+++ b/arch/x86/kernel/i8259.c
@@ -299,13 +299,31 @@ static void unmask_8259A(void)
static void init_8259A(int auto_eoi)
{
unsigned long flags;
+ unsigned char probe_val = ~(1 << PIC_CASCADE_IR);
+ unsigned char new_val;
i8259A_auto_eoi = auto_eoi;
raw_spin_lock_irqsave(&i8259A_lock, flags);
- outb(0xff, PIC_MASTER_IMR); /* mask all of 8259A-1 */
+ /*
+ * Check to see if we have a PIC.
+ * Mask all except the cascade and read
+ * back the value we just wrote. If we don't
+ * have a PIC, we will read 0xff as opposed to the
+ * value we wrote.
+ */
outb(0xff, PIC_SLAVE_IMR); /* mask all of 8259A-2 */
+ outb(probe_val, PIC_MASTER_IMR);
+ new_val = inb(PIC_MASTER_IMR);
+ if (new_val != probe_val) {
+ printk(KERN_INFO "Using NULL legacy PIC\n");
+ legacy_pic = &null_legacy_pic;
+ raw_spin_unlock_irqrestore(&i8259A_lock, flags);
+ return;
+ }
+
+ outb(0xff, PIC_MASTER_IMR); /* mask all of 8259A-1 */
/*
* outb_pic - this has to work on a wide range of PC hardware.