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>

1 files changed, 16 insertions, 5 deletions

diff --git a/drivers/platform/x86/toshiba_acpi.c b/drivers/platform/x86/toshiba_acpi.c
index 13ef8c37471d..dcdc1f4a4624 100644
--- 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);
 }