toshiba_acpi: Fix machines that don't support HCI_SYSTEM_EVENT

The Satellite C670-10V generates notifications for hotkeys but does
not support HCI_SYSTEM_EVENT. As a result when a hotkey is pressed
it gets stuck in an infinite loop in toshiba_acpi_notify. To fix
this, detect whether or not HCI_SYSTEM_EVENT is supported up-front
and don't try to read system events if it isn't supported. In
addition, limit the number of retries when reading HCI_SYSTEM_EVENT
fails so that this loop cannot run unbounded.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

diff --git a/drivers/platform/x86/toshiba_acpi.c b/drivers/platform/x86/toshiba_acpi.c
index 13ef8c3..dcdc1f4 100644 (file)
--- a/drivers/platform/x86/toshiba_acpi.c
+++ b/drivers/platform/x86/toshiba_acpi.c
@@ -121,6 +121,7 @@ struct toshiba_acpi_dev {
        int illumination_supported:1;
        int video_supported:1;
        int fan_supported:1;
+       int system_event_supported:1;
 
        struct mutex mutex;
 };
@@ -724,7 +725,7 @@ static int keys_proc_show(struct seq_file *m, void *v)
        u32 hci_result;
        u32 value;
 
-       if (!dev->key_event_valid) {
+       if (!dev->key_event_valid && dev->system_event_supported) {
                hci_read1(dev, HCI_SYSTEM_EVENT, &value, &hci_result);
                if (hci_result == HCI_SUCCESS) {
                        dev->key_event_valid = 1;
@@ -964,6 +965,8 @@ static int __devinit toshiba_acpi_add(struct acpi_device *acpi_dev)
 
        /* enable event fifo */
        hci_write1(dev, HCI_SYSTEM_EVENT, 1, &hci_result);
+       if (hci_result == HCI_SUCCESS)
+               dev->system_event_supported = 1;
 
        props.type = BACKLIGHT_PLATFORM;
        props.max_brightness = HCI_LCD_BRIGHTNESS_LEVELS - 1;
@@ -1032,12 +1035,15 @@ static void toshiba_acpi_notify(struct acpi_device *acpi_dev, u32 event)
 {
        struct toshiba_acpi_dev *dev = acpi_driver_data(acpi_dev);
        u32 hci_result, value;
+       int retries = 3;
 
-       if (event != 0x80)
+       if (!dev->system_event_supported || event != 0x80)
                return;
+
        do {
                hci_read1(dev, HCI_SYSTEM_EVENT, &value, &hci_result);
-               if (hci_result == HCI_SUCCESS) {
+               switch (hci_result) {
+               case HCI_SUCCESS:
                        if (value == 0x100)
                                continue;
                        /* act on key press; ignore key release */
@@ -1049,14 +1055,19 @@ static void toshiba_acpi_notify(struct acpi_device *acpi_dev, u32 event)
                                pr_info("Unknown key %x\n",
                                       value);
                        }
-               } else if (hci_result == HCI_NOT_SUPPORTED) {
+                       break;
+               case HCI_NOT_SUPPORTED:
                        /* This is a workaround for an unresolved issue on
                         * some machines where system events sporadically
                         * become disabled. */
                        hci_write1(dev, HCI_SYSTEM_EVENT, 1, &hci_result);
                        pr_notice("Re-enabled hotkeys\n");
+                       /* fall through */
+               default:
+                       retries--;
+                       break;
                }
-       } while (hci_result != HCI_EMPTY);
+       } while (retries && hci_result != HCI_EMPTY);
 }