[PATCH v3 1/3] usb: core: Fix SuperSpeed root hub wMaxPacketSize
From: Michal Pecio
Date: Mon May 18 2026 - 01:32:21 EST
There is no good reason to have wBytesPerInterval < wMaxPacketSize -
either one is too low or the other too high, and we may want to warn
about such descriptors. Start with cleaning up our own root hubs.
USB 3.2 section 10.15.1 sets wMaxPacketSize and wBytesPerInterval of
SuperSpeed hub status endpoints at 2 bytes, so reduce wMaxPacketSize
from its former value of 4, which was derived from USB 2.0 spec and
the kernel's USB_MAXCHILDREN limit. They don't apply because USB 3.2
10.15.2.1 specifies SuperSpeed hubs to have up to 15 ports.
Suggested-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Signed-off-by: Michal Pecio <michal.pecio@xxxxxxxxx>
---
drivers/usb/core/hcd.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 89221f1ce769..b181b43a35dc 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -328,9 +328,7 @@ static const u8 ss_rh_config_descriptor[] = {
USB_DT_ENDPOINT, /* __u8 ep_bDescriptorType; Endpoint */
0x81, /* __u8 ep_bEndpointAddress; IN Endpoint 1 */
0x03, /* __u8 ep_bmAttributes; Interrupt */
- /* __le16 ep_wMaxPacketSize; 1 + (MAX_ROOT_PORTS / 8)
- * see hub.c:hub_configure() for details. */
- (USB_MAXCHILDREN + 1 + 7) / 8, 0x00,
+ 0x02, 0x00, /* __le16 ep_wMaxPacketSize; 2 bytes per USB3 10.15.1 */
0x0c, /* __u8 ep_bInterval; (256ms -- usb 2.0 spec) */
/* one SuperSpeed endpoint companion descriptor */
--
2.48.1