patch "USB: usbfs: compute urb->actual_length for isochronous" added to usb-testing

This is a note to let you know that I've just added the patch titled

    USB: usbfs: compute urb->actual_length for isochronous

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-testing branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will be merged to the usb-next branch sometime soon, after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.

From: Alan Stern <[email protected]>
Date: Wed, 8 Nov 2017 12:23:17 -0500
Subject: USB: usbfs: compute urb->actual_length for isochronous

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.

---
 drivers/usb/core/devio.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

index c3aaafc25a04..2edb4e7b2ab8 100644
@@ -1820,6 +1820,18 @@ static int proc_unlinkurb(struct usb_dev_state *ps, void __user *arg)
 	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;

@@ -1827,6 +1839,7 @@ static int processcompl(struct async *as, void __user * __user *arg)
 	void __user *addr = as->userurb;
 	unsigned int i;
 
+	compute_isochronous_actual_length(urb);
 	if (as->userbuffer && urb->actual_length) {
 		if (copy_urb_data_to_user(as->userbuffer, urb))
 			goto err_out;

@@ -1995,6 +2008,7 @@ static int processcompl_compat(struct async *as, void __user * __user *arg)
 	void __user *addr = as->userurb;
 	unsigned int i;
 
+	compute_isochronous_actual_length(urb);
 	if (as->userbuffer && urb->actual_length) {
 		if (copy_urb_data_to_user(as->userbuffer, urb))
 			return -EFAULT;

2.15.0