On Sat, 12 May 2007, Jayaprakash Shanmugam wrote: > Hi All, > > I have a EHCI host connected to 4 USB devices (dev1, dev2, dev3 and > dev4). I have two processes that make use of these devices through a > kernel object. I have some vendor commands (through EP-0) to all the > devices. Apart from this, dev1 has EP2 ( in ) bulk, dev2 has EP2 ( > in ) interrupt and dev4 has EP6 ( out ) bulk. There are 3 processes > in our system. From Process1, I read EP2 from dev1 periodically (for > every 30 ms) and send it to EP6 of dev4. The other process Process2, > reads the EP2 interrupt endpoint of dev2 periodically. The last > process Process3, tries to write to dev4 EP-0 quite frequently (every > 3 seconds). Sometimes, the usb_control_msg() receives timeout error. > I am not able to understand why it should return timeout error > intermittently. > > 1) When the control endpoint and bulk endpoint are used in a device, > Can I not use both of them simultaneously ?
The Linux host software allows it. However the device itself might have some restrictions (although it shouldn't). > 2) When I tried to write to EP-0 of a device, the other process who > sends periodic data to EP-2 of the same device How can that be? You said above that on both dev1 and dev2, ep2 is in, not out. > receives the error > message - ep0out timeout error. Why should the process receive this > debug message (from the timeout handler in the usb_submit_urb() ) Most likely you misunderstood what happened. Please provide logs demonstrating the problem. > 3) When I tried to write to EP-0 of a device (while the other process > sending data to EP-2 of the same device periodically), the device > received the data succesfully. But, the host says the request is > timeout. Does it mean that the ACK for the EP-0 packet is received by > the URB who waits for ACK for the Bulk transfer. ep0 transfers involve several packets, so it doesn't make sense to talk about "the ACK for the EP-0 packet". If the device receives the data correctly and the host reports a timeout, it means that the device continues to send NAK packets even after it has received the data. > This mail may be huge. Since I am not able to understand the behavior > I wanted to give the full details of the issue. > > Note: I am running Linux 2.6 on MPC 8270 with Philips PCI - USB converter 2.6.what? Alan Stern ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
