On Wednesday 25 November 2009 05:43:37 Ramesh Rajagopal wrote: > > On Wednesday 11 November 2009 12:43:38 Ramesh Rajagopal wrote: > > > > > > Thank you for the reply. The webcam is linux based and I am using the > > > UVC gadget driver of linux kernel 2.6.10. > > > In this kernel I don't see any example doing UVC bulk transfer. It is > > > working perfectly with ISOC. > > > Can you please let me know, if there is any example code that does UVC > > > bulk transfer ? I couldn't find it any. > > > > The UVC gadget driver I wrote uses isochronous transfers. It should be > > possible to use bulk transfers by modifying the driver, but there's no > > code sample that I'm aware of. > > Does this mean, I have to change the musb gadget driver code? I changed my > driver which registers with musb. I didn't chane anything on the musb gadget > driver.
You shouldn't need to change the musb gadget driver code (unless there's a bulk-specific bug in the musb gadget driver of course). You will need to change the UVC gadget driver code though. > > > The uvc specification is not clear enough to distinguish ISOC and BULK > > > transfer atleast from my understanding. > > > > > > While doing ISOC transfer, we have an alternate Interface Setting, when > > > we get a SET_INTERFACE we start transferring the UVC header first alone > > > to start the transfer. There after each IN token from host will carry > > > the frames if any, otherwise header alone goes. > > > > > > In case of BULK, with alternate settings, the host machine hangs. > > > SET_INTERFACE (alternateSetting set 1), Why is it like that? > > > > According to the UVC specification, streaming interfaces with bulk > > endpoints don't use alternate settings. > > > > This is actually a problem, as the UVC specification doesn't provide any > > way for bulk devices to detect when the host starts and stops streaming. > > Do you aware when do I start sending packets to the host? In case of ISOC, > we start sending packets when get SET_INTERFACE (enabling the alternate > setting) request. Please let me know. I don't know, and that's the real problem. I think you should start sending data when you receive the first bulk packet. I'm not sure if there's a way to be notified of that though. You could then stop the stream when no bulk packet is received for some time. > > > So I removed alternate settings and till enumeration it is proper. Then > > > After I get VS_PROBE_COMMIT from the host, I start transferring exactly > > > same like ISOC, but I don't see any video on the host and no more > > > proceedings from here. The data is not going from the FIFO, hence I am > > > not getting any more TX interrupt from my device. > > > > > > I am attaching my devices descriptor as well as host side logs. Please > > > find the attachment. Please let me know, is there any link talk about > > > BULK transfer or example. > > > > The descriptors look correct at first glance. The log shows that the > > driver doesn't receive any bulk packet (assuming the trace parameter has > > been set to 255). This seems to indicate a low-level problem, probably on > > the device side. > > My guess is that the device doesn't sent bulk packets. That would be easy > > to verify if you have access to a USB analyzer. If the assumption is > > correct, the problem is on the device side. > > I see the packets are on the wire. USB Analyzer shows me the data and even > I verified the header data, it looks correct, Now I am not getting back the > ACK from the host. Thanks for your Reply. You're welcome. -- Regards, Laurent Pinchart _______________________________________________ Linux-uvc-devel mailing list Linux-uvc-devel@lists.berlios.de https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
