On Fri, Mar 15, 2013 at 10:47:50AM -0400, Alan Stern wrote:
> On Fri, 15 Mar 2013, Peter Chen wrote:
>
> > On Thu, Mar 14, 2013 at 10:59:45AM -0400, Alan Stern wrote:
> > > On Thu, 14 Mar 2013, Peter Chen wrote:
> > >
> > > > /home/b29397/work/code/git/linus/linux-2.6/drivers/usb/host/xhci-ring.c: In function ‘handle_port_status’:
> > > > /home/b29397/work/code/git/linus/linux-2.6/drivers/usb/host/xhci-ring.c:1580: warning: ‘hcd’ may be used uninitialized in this function
> > > >
> > > > Signed-off-by: Peter Chen <peter.chen@xxxxxxxxxxxxx>
> > > > ---
> > > > drivers/usb/host/xhci-ring.c | 4 ++--
> > > > 1 files changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> > > > index 8828754..17dace0 100644
> > > > --- a/drivers/usb/host/xhci-ring.c
> > > > +++ b/drivers/usb/host/xhci-ring.c
> > > > @@ -1588,6 +1588,8 @@ static void handle_port_status(struct xhci_hcd *xhci,
> > > > __le32 __iomem **port_array;
> > > > bool bogus_port_status = false;
> > > >
> > > > + /* Find the right roothub. */
> > > > + hcd = xhci_to_hcd(xhci);
> > > > /* Port status change events always have a successful completion code */
> > > > if (GET_COMP_CODE(le32_to_cpu(event->generic.field[2])) != COMP_SUCCESS) {
> > > > xhci_warn(xhci, "WARN: xHC returned failed port status event\n");
> > > > @@ -1629,8 +1631,6 @@ static void handle_port_status(struct xhci_hcd *xhci,
> > > > * into the index into the ports on the correct split roothub, and the
> > > > * correct bus_state structure.
> > > > */
> > > > - /* Find the right roothub. */
> > > > - hcd = xhci_to_hcd(xhci);
> > > > if ((major_revision == 0x03) != (hcd->speed == HCD_USB3))
> > > > hcd = xhci->shared_hcd;
> > >
> > > You forgot to move these last two lines along with the first two.
> >
> > No, major_revision is got above it.
> >
> > In fact, the old logic is no problem due to flag bogus_port_status.
>
> This doesn't matter. Your change makes the code more fragile and
> harder to understand, because in your version "hcd" is initialized in
> two separate places. The initialization should remain a single block
> of code.
>
> "Works okay" isn't good enough. A lot of programmers seem to have
> trouble absorbing this concept. The code needs to be _clear_, because
> it needs to continue to work correctly after other people make changes.
> If those other people can't understand it then they are likely to break
> the code.
I agree with you. How about below version:
drivers/usb/host/xhci-ring.c | 39 ++++++++++++++++++++-------------------
1 files changed, 20 insertions(+), 19 deletions(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 8828754..6138af2 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1588,25 +1588,18 @@ static void handle_port_status(struct xhci_hcd *xhci,
__le32 __iomem **port_array;
bool bogus_port_status = false;
- /* Port status change events always have a successful completion code */
- if (GET_COMP_CODE(le32_to_cpu(event->generic.field[2])) != COMP_SUCCESS) {
- xhci_warn(xhci, "WARN: xHC returned failed port status event\n");
- xhci->error_bitmask |= 1 << 8;
- }
- port_id = GET_PORT_ID(le32_to_cpu(event->generic.field[0]));
- xhci_dbg(xhci, "Port Status Change Event for port %d\n", port_id);
-
- max_ports = HCS_MAX_PORTS(xhci->hcs_params1);
- if ((port_id <= 0) || (port_id > max_ports)) {
- xhci_warn(xhci, "Invalid port id %d\n", port_id);
- bogus_port_status = true;
- goto cleanup;
- }
-
/* Figure out which usb_hcd this port is attached to:
* is it a USB 3.0 port or a USB 2.0/1.1 port?
*/
+ port_id = GET_PORT_ID(le32_to_cpu(event->generic.field[0]));
+ xhci_dbg(xhci, "Port Status Change Event for port %d\n", port_id);
+
major_revision = xhci->port_array[port_id - 1];
+ /* Find the right roothub. */
+ hcd = xhci_to_hcd(xhci);
+ if ((major_revision == 0x03) != (hcd->speed == HCD_USB3))
+ hcd = xhci->shared_hcd;
+
if (major_revision == 0) {
xhci_warn(xhci, "Event for port %u not in "
"Extended Capabilities, ignoring.\n",
@@ -1621,6 +1614,18 @@ static void handle_port_status(struct xhci_hcd *xhci,
bogus_port_status = true;
goto cleanup;
}
+ /* Port status change events always have a successful completion code */
+ if (GET_COMP_CODE(le32_to_cpu(event->generic.field[2])) != COMP_SUCCESS) {
+ xhci_warn(xhci, "WARN: xHC returned failed port status event\n");
+ xhci->error_bitmask |= 1 << 8;
+ }
+
+ max_ports = HCS_MAX_PORTS(xhci->hcs_params1);
+ if ((port_id <= 0) || (port_id > max_ports)) {
+ xhci_warn(xhci, "Invalid port id %d\n", port_id);
+ bogus_port_status = true;
+ goto cleanup;
+ }
/*
* Hardware port IDs reported by a Port Status Change Event include USB
@@ -1629,10 +1634,6 @@ static void handle_port_status(struct xhci_hcd *xhci,
* into the index into the ports on the correct split roothub, and the
* correct bus_state structure.
*/
- /* Find the right roothub. */
- hcd = xhci_to_hcd(xhci);
- if ((major_revision == 0x03) != (hcd->speed == HCD_USB3))
- hcd = xhci->shared_hcd;
bus_state = &xhci->bus_state[hcd_index(hcd)];
if (hcd->speed == HCD_USB3)
port_array = xhci->usb3_ports;
--
Best Regards,
Peter Chen
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