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authorAlan Stern <stern@rowland.harvard.edu>2008-04-28 11:06:28 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2008-07-21 15:15:47 -0700
commit24618b0cd42f936cda461bdf6144670a5c925178 (patch)
treedfcc0d831eb24f7466bbb3ebb2a69b3d93622120 /drivers/usb/core
parentb01b03f3ad82b4293f6ca4da9b2692b6a377c609 (diff)
USB: debounce before unregistering
This patch (as1080) makes a significant change to the way khubd handles port connect-change and enable-change events. Both types of event are now debounced, and the debouncing is carried out _before_ an existing usb_device is unregistered, instead of afterward. This means that drivers will have to deal with longer runs of errors when a device is unplugged, but they are supposed to be prepared for that in any case. The advantage is that when an enable-change occurs (caused for example by electromagnetic interference), the debouncing period will provide time for the cause of the problem to die away. A simple port reset (added in a forthcoming patch) will then allow us to recover from the fault. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb/core')
-rw-r--r--drivers/usb/core/hub.c31
1 files changed, 19 insertions, 12 deletions
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index d14da2123eb..d741b945742 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2673,9 +2673,10 @@ static void hub_port_connect_change(struct usb_hub *hub, int port1,
struct usb_device *hdev = hub->hdev;
struct device *hub_dev = hub->intfdev;
struct usb_hcd *hcd = bus_to_hcd(hdev->bus);
- u16 wHubCharacteristics = le16_to_cpu(hub->descriptor->wHubCharacteristics);
+ unsigned wHubCharacteristics =
+ le16_to_cpu(hub->descriptor->wHubCharacteristics);
int status, i;
-
+
dev_dbg (hub_dev,
"port %d, status %04x, change %04x, %s\n",
port1, portstatus, portchange, portspeed (portstatus));
@@ -2684,30 +2685,36 @@ static void hub_port_connect_change(struct usb_hub *hub, int port1,
set_port_led(hub, port1, HUB_LED_AUTO);
hub->indicator[port1-1] = INDICATOR_AUTO;
}
-
- /* Disconnect any existing devices under this port */
- if (hdev->children[port1-1])
- usb_disconnect(&hdev->children[port1-1]);
- clear_bit(port1, hub->change_bits);
#ifdef CONFIG_USB_OTG
/* during HNP, don't repeat the debounce */
if (hdev->bus->is_b_host)
- portchange &= ~USB_PORT_STAT_C_CONNECTION;
+ portchange &= ~(USB_PORT_STAT_C_CONNECTION |
+ USB_PORT_STAT_C_ENABLE);
#endif
- if (portchange & USB_PORT_STAT_C_CONNECTION) {
+ /* Try to use the debounce delay for protection against
+ * port-enable changes caused, for example, by EMI.
+ */
+ if (portchange & (USB_PORT_STAT_C_CONNECTION |
+ USB_PORT_STAT_C_ENABLE)) {
status = hub_port_debounce(hub, port1);
if (status < 0) {
if (printk_ratelimit())
dev_err (hub_dev, "connect-debounce failed, "
"port %d disabled\n", port1);
- goto done;
+ portstatus &= ~USB_PORT_STAT_CONNECTION;
+ } else {
+ portstatus = status;
}
- portstatus = status;
}
- /* Return now if nothing is connected */
+ /* Disconnect any existing devices under this port */
+ if (hdev->children[port1-1])
+ usb_disconnect(&hdev->children[port1-1]);
+ clear_bit(port1, hub->change_bits);
+
+ /* Return now if debouncing failed or nothing is connected */
if (!(portstatus & USB_PORT_STAT_CONNECTION)) {
/* maybe switch power back on (e.g. root hub was reset) */