[PATCH] USB UHCI: Detect invalid ports
This patch changes the way uhci-hcd detects valid ports. The
specification doesn't mention any way to find out how many ports a
controller has, so the driver has to use some heuristics, reading the port
status and control register and deciding whether the value makes sense.
With this patch the driver will recognize a typical failure mode (all bits
set to one) for nonexistent ports and won't assume there are always at
least 2 ports -- such an assumption seems silly if the heuristics have
already shown that the ports don't exist.
Signed-off-by: Alan Stern <[EMAIL PROTECTED]>
Signed-off-by: Greg Kroah-Hartman <[EMAIL PROTECTED]>
---
commit e07fefa6b212f43c40fdbc1a62de690d91a4b617
tree 8426cdb4a4b8c7b9a0ce2cc360beebf9499d9572
parent 486e2df6ce213d0c776befdf3fe5ffc61dd61688
author Alan Stern <[EMAIL PROTECTED]> Tue, 31 May 2005 16:33:21 -0400
committer Greg Kroah-Hartman <[EMAIL PROTECTED]> Mon, 27 Jun 2005 14:44:00 -0700
drivers/usb/host/uhci-hcd.c | 14 +++++++-------
1 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/usb/host/uhci-hcd.c b/drivers/usb/host/uhci-hcd.c
--- a/drivers/usb/host/uhci-hcd.c
+++ b/drivers/usb/host/uhci-hcd.c
@@ -495,24 +495,24 @@ static int uhci_reset(struct usb_hcd *hc
/* The UHCI spec says devices must have 2 ports, and goes on to say
* they may have more but gives no way to determine how many there
- * are. However, according to the UHCI spec, Bit 7 of the port
+ * are. However according to the UHCI spec, Bit 7 of the port
* status and control register is always set to 1. So we try to
- * use this to our advantage.
+ * use this to our advantage. Another common failure mode when
+ * a nonexistent register is addressed is to return all ones, so
+ * we test for that also.
*/
for (port = 0; port < (io_size - USBPORTSC1) / 2; port++) {
unsigned int portstatus;
portstatus = inw(uhci->io_addr + USBPORTSC1 + (port * 2));
- if (!(portstatus & 0x0080))
+ if (!(portstatus & 0x0080) || portstatus == 0xffff)
break;
}
if (debug)
dev_info(uhci_dev(uhci), "detected %d ports\n", port);
- /* Anything less than 2 or greater than 7 is weird,
- * so we'll ignore it.
- */
- if (port < 2 || port > UHCI_RH_MAXCHILD) {
+ /* Anything greater than 7 is weird so we'll ignore it. */
+ if (port > UHCI_RH_MAXCHILD) {
dev_info(uhci_dev(uhci), "port count misdetected? "
"forcing to 2 ports\n");
port = 2;
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