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SubjectRe: [PATCH 2/9] drivers/acpi/asus_acpi.c: Correct use of ! and &
On Wed, 27 Feb 2008 19:29:15 +0100 Mark Pearson <devnull.port@googlemail.com> wrote:

> Karol Kozimor wrote:
> > On 26-02-2008, at 21:42, Julia Lawall wrote:
> >> if (invert) /* invert target value */
> >> - led_out = !led_out & 0x1;
> >> + led_out = !(led_out & 0x1);
> >>
> >> if (!write_acpi_int(hotk->handle, ledname, led_out, NULL))
> >> printk(KERN_WARNING "Asus ACPI: LED (%s) write failed\n",
> >
> >
> > IIRC we're just supposed to flip the last bit here, so the original code
> > is correct.
> > Best regards,
> >
>
> Seems an odd way of doing:
>
> led_out ^= 0x01;

It does.

> It this due to some optimisation?

Surely not ;)

That code has been there for many years.

I changed the patch to this:

--- a/drivers/acpi/asus_acpi.c~drivers-acpi-asus_acpic-correct-use-of-and
+++ a/drivers/acpi/asus_acpi.c
@@ -610,7 +610,7 @@ write_led(const char __user * buffer, un
(led_out) ? (hotk->status | ledmask) : (hotk->status & ~ledmask);

if (invert) /* invert target value */
- led_out = !led_out & 0x1;
+ led_out = !led_out;

if (!write_acpi_int(hotk->handle, ledname, led_out, NULL))
printk(KERN_WARNING "Asus ACPI: LED (%s) write failed\n",
_


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