Hi Alan,
在 2017年11月07日 23:18, Alan Stern 写道:
On Tue, 7 Nov 2017, wlf wrote:
That sounds like a good idea. Minas, does the following patch fix your
problem?
In theory we could do this calculation for every isochronous URB, not
just those coming from usbfs. But I don't think there's any point,
since the USB class drivers don't use it.
Alan Stern
Index: usb-4.x/drivers/usb/core/devio.c
===================================================================
--- usb-4.x.orig/drivers/usb/core/devio.c
+++ usb-4.x/drivers/usb/core/devio.c
@@ -1828,6 +1828,18 @@ static int proc_unlinkurb(struct usb_dev
return 0;
}
+static void compute_isochronous_actual_length(struct urb *urb)
+{
+ unsigned 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;
@@ -1835,6 +1847,8 @@ 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 (copy_urb_data_to_user(as->userbuffer, urb))
goto err_out;
@@ -2003,6 +2017,8 @@ 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 (copy_urb_data_to_user(as->userbuffer, urb))
return -EFAULT;
Yeah, it's a good idea to calculate the urb actual length in the devio
driver.
Your patch seems good, and I think we can do a small optimization base
your patch,
like the following patch:
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index bd94192..a2e7b97 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -1664,6 +1664,9 @@ static int processcompl(struct async *as, void
__user * __user *arg)
void __user *addr = as->userurb;
unsigned int i;
+ if (usb_endpoint_xfer_isoc(&urb->ep->desc))
+ compute_isochronous_actual_length(urb);
+
if (as->userbuffer && urb->actual_length) {
if (copy_urb_data_to_user(as->userbuffer, urb))
goto err_out;
@@ -1833,6 +1836,9 @@ static int processcompl_compat(struct async *as,
void __user * __user *arg)
void __user *addr = as->userurb;
unsigned int i;
+ if (usb_endpoint_xfer_isoc(&urb->ep->desc))
+ compute_isochronous_actual_length(urb);
+
Well, this depends on whether you want to optimize for space or for
speed. I've been going for space. And since usbfs is inherently
rather slow, I don't think this will make any significant speed
difference. So I don't think adding the extra tests is worthwhile.
(Besides, if you really wanted to do it this way, you should have moved
the test for "urb->number_of_packets > 0" into the callers instead of
adding an additional test of the endpoint type.)
Yes, agree with you.
However, nobody has answered my original question: Does the patch
actually fix the problem?
I test your patch on Rockchip RK3188 platform, use UsbWebCamera APP by
Serenegiant
(libusb + devio) with usb camera, it work well.
Alan Stern
--
吴良峰 William.Wu
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