wusbcore: fix root hub hub_status_data to only return > 0 if status has actually changed

The hub_status_data function on the wireless USB root hub controller
(wusbhc_rh_status_data) always returns a positive value even if no ports
have changed.  This patch updates wusbhc_rh_status_data to only return a
positive value if the root hub status needs to be queried.  The current
implementation can also leave the upper bits of the port bitmap
uninitialized if wusbhc->ports_max is not one less than an even multiple
of 8.  This patch fixes that as well by initializing the buffer to 0.

Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 18 insertions, 10 deletions

diff --git a/drivers/usb/wusbcore/rh.c b/drivers/usb/wusbcore/rh.c
index bdb0cc3046b5..fe8bc777ab88 100644
--- a/drivers/usb/wusbcore/rh.c
+++ b/drivers/usb/wusbcore/rh.c
@@ -141,18 +141,26 @@ static int wusbhc_rh_port_reset(struct wusbhc *wusbhc, u8 port_idx)
 int wusbhc_rh_status_data(struct usb_hcd *usb_hcd, char *_buf)
 {
         struct wusbhc *wusbhc = usb_hcd_to_wusbhc(usb_hcd);
-        size_t cnt, size;
-        unsigned long *buf = (unsigned long *) _buf;
+        size_t cnt, size, bits_set = 0;
 
         /* WE DON'T LOCK, see comment */
-        size = wusbhc->ports_max + 1 /* hub bit */;
-        size = (size + 8 - 1) / 8;      /* round to bytes */
-        for (cnt = 0; cnt < wusbhc->ports_max; cnt++)
-                if (wusb_port_by_idx(wusbhc, cnt)->change)
-                        set_bit(cnt + 1, buf);
-                else
-                        clear_bit(cnt + 1, buf);
-        return size;
+        /* round up to bytes.  Hub bit is bit 0 so add 1. */
+        size = DIV_ROUND_UP(wusbhc->ports_max + 1, 8);
+
+        /* clear the output buffer. */
+        memset(_buf, 0, size);
+        /* set the bit for each changed port. */
+        for (cnt = 0; cnt < wusbhc->ports_max; cnt++) {
+
+                if (wusb_port_by_idx(wusbhc, cnt)->change) {
+                        const int bitpos = cnt+1;
+
+                        _buf[bitpos/8] |= (1 << (bitpos % 8));
+                        bits_set++;
+                }
+        }
+
+        return bits_set ? size : 0;
 }
 EXPORT_SYMBOL_GPL(wusbhc_rh_status_data);