[PATCH 3.2 31/79] USB: usbfs: compute urb->actual_length for isochronous

Ben Hutchings
2018-02-11T04:33:43Z

From: Alan Stern <stern@rowland.harvard.edu>

commit 2ef47001b3ee3ded579b7532ebdcf8680e4d8c54 upstream.

The USB kerneldoc says that the actual_length field "is read in
non-iso completion functions", but the usbfs driver uses it for all
URB types in processcompl(). Since not all of the host controller
drivers set actual_length for isochronous URBs, programs using usbfs
with some host controllers don't work properly. For example, Minas
reports that a USB camera controlled by libusb doesn't work properly
with a dwc2 controller.

It doesn't seem worthwhile to change the HCDs and the documentation,
since the in-kernel USB class drivers evidently don't rely on
actual_length for isochronous transfers. The easiest solution is for
usbfs to calculate the actual_length value for itself, by adding up
the lengths of the individual packets in an isochronous transfer.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Minas Harutyunyan <Minas.Harutyunyan@synopsys.com>
Reported-and-tested-by: wlf <wulf@rock-chips.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/usb/core/devio.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -1402,6 +1402,18 @@ static int proc_unlinkurb(struct dev_sta
return 0;
}

+static void compute_isochronous_actual_length(struct urb *urb)
+{
+ unsigned int i;
+
+ if (urb->number_of_packets > 0) {
+ urb->actual_length = 0;
+ for (i = 0; i < urb->number_of_packets; i++)
+ urb->actual_length +=
+ urb->iso_frame_desc[i].actual_length;
+ }
+}
+
static int processcompl(struct async *as, void __user * __user *arg)
{
struct urb *urb = as->urb;
@@ -1409,6 +1421,7 @@ static int processcompl(struct async *as
void __user *addr = as->userurb;
unsigned int i;

+ compute_isochronous_actual_length(urb);
if (as->userbuffer && urb->actual_length) {
if (urb->number_of_packets > 0) /* Isochronous */
i = urb->transfer_buffer_length;
@@ -1581,6 +1594,7 @@ static int processcompl_compat(struct as
void __user *addr = as->userurb;
unsigned int i;

+ compute_isochronous_actual_length(urb);
if (as->userbuffer && urb->actual_length) {
if (urb->number_of_packets > 0) /* Isochronous */
i = urb->transfer_buffer_length;