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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