EP-0 returns timeout even when data is received by the device.

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 ?

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 receives the error
message - ep0out timeout error.  Why should the process receive this
debug message (from the timeout handler in the usb_submit_urb() )

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.

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

Thanks,
Jayaprakash.

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