usb: ch9: fix up MaxStreams helper

According to USB 3.0 Specification Table 9-22, if
bmAttributes [4:0] are set to zero, it means "no
streams supported", but the way this helper was
defined on Linux, we will *always* have one stream
which might cause several problems.

For example on DWC3, we would tell the controller
endpoint has streams enabled and yet start transfers
with Stream ID set to 0, which would goof up the host
side.

While doing that, convert the macro to an inline
function due to the different checks we now need.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 19 insertions, 1 deletions

diff --git a/include/linux/usb/ch9.h b/include/linux/usb/ch9.h
index d5da6c68c250..61b29057b054 100644
--- a/include/linux/usb/ch9.h
+++ b/include/linux/usb/ch9.h
@@ -605,8 +605,26 @@ struct usb_ss_ep_comp_descriptor {
 } __attribute__ ((packed));
 
 #define USB_DT_SS_EP_COMP_SIZE		6
+
 /* Bits 4:0 of bmAttributes if this is a bulk endpoint */
-#define USB_SS_MAX_STREAMS(p)		(1 << ((p) & 0x1f))
+static inline int
+usb_ss_max_streams(const struct usb_ss_ep_comp_descriptor *comp)
+{
+	int		max_streams;
+
+	if (!comp)
+		return 0;
+
+	max_streams = comp->bmAttributes & 0x1f;
+
+	if (!max_streams)
+		return 0;
+
+	max_streams = 1 << max_streams;
+
+	return max_streams;
+}
+
 /* Bits 1:0 of bmAttributes if this is an isoc endpoint */
 #define USB_SS_MULT(p)			(1 + ((p) & 0x3))