>>> On 12.04.14 at 07:56, <k...@microsoft.com> wrote:
> --- a/arch/x86/kernel/i8259.c
> +++ b/arch/x86/kernel/i8259.c
> @@ -299,11 +299,30 @@ 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);
>
> + /*
> + * 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 (probe_val != new_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(0xff, PIC_SLAVE_IMR); /* mask all of 8259A-2 */
And I guess you should delete this last line now that this is already
being done slightly earlier - having it done twice is possibly going to
confuse future readers (in that they might ask themselves or others
whether this really needs to be done twice).
Jan
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