Fix forcedeth hibernate/wake-on-lan problems

This patch is the minimal amount of code needed to support
wake-on-lan in platform mode properly (i.e. "ethtool -s eth0 wol g"
is sufficient, no additional magic needed) for me.

This is derived from David Brownells patch
(http://lists.laptop.org/pipermail/devel/2007-April/004691.html).
However I decided to move the hook into pci-acpi.c since the other
two pci hooks also live there and pci and acpi are the only users of
the platform_enable_wakeup-hook.

As a 'side-effect' this also makes wake on usb activity work for me
and I had to disable usb wakeup (which is enabled by default) using
the power/wakeup sysfs functionality ("echo disabled >
${sysfs_path_to_device}/power/wakeup").

(BTW I first thought the 'immediate reboot because of usb wake' effect is
caused by the optical mouse generating a wake event, but it rather
seems to be a problem with a flaky secondary usb host controller,
which sees a connected device where nothing is attached)
Signed-off-by: Tobias Diedrich <ranma+kernel@tdiedrich.de>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/pci/pci-acpi.c

@@ -315,6 +315,25 @@ static pci_power_t acpi_pci_choose_state(struct pci_dev *pdev,
 	}
 	return PCI_POWER_ERROR;
 }
+
+static int acpi_platform_enable_wakeup(struct device *dev, int is_on)
+{
+	struct acpi_device	*adev;
+	int			status;
+
+	if (!device_can_wakeup(dev))
+		return -EINVAL;
+
+	if (is_on && !device_may_wakeup(dev))
+		return -EINVAL;
+
+	status = acpi_bus_get_device(DEVICE_ACPI_HANDLE(dev), &adev);
+	if (status < 0)
+		return status;
+
+	adev->wakeup.state.enabled = !!is_on;
+	return 0;
+}
 #endif
 
 static int acpi_pci_set_power_state(struct pci_dev *dev, pci_power_t state)
@@ -399,6 +418,7 @@ static int __init acpi_pci_init(void)
 		return 0;
 #ifdef	CONFIG_ACPI_SLEEP
 	platform_pci_choose_state = acpi_pci_choose_state;
+	platform_enable_wakeup = acpi_platform_enable_wakeup;
 #endif
 	platform_pci_set_power_state = acpi_pci_set_power_state;
 	return 0;