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Re: IOUSBDevice->DeviceRequest( ) times out

Subject: Re: IOUSBDevice->DeviceRequest( ) times out
From: David Ferguson <email@hidden>
Date: Mon, 28 Mar 2005 15:28:42 -0800
Delivered-to: email@hidden
Delivered-to: email@hidden

I assume you mean you are testing a device to see if it responds to USB device requests, and you're trying to do it from your driver.

First - you need to look at what's going out on the bus. Is the device responding, or is it NAKing? Check that the request is well formed -- particularly check that the wValue field (descriptor type & index) is in the correct USB bus order (little endian - normally displayed on a CATC as <index><type> (ie 0x0001), but specified on the big-ending Macintosh as <type><index> (0x0100). This is only specified in the USB spec as "descriptor type in the high byte, and index in the low byte".

If that's what's happening you need to fix your device's firmware to respond with STALL any request for an unknown descriptor type (like 0!), you should do this for any bRequests, indecies out of range, etc.

Hopefully that will help.

David Ferguson
USB Software Team
Apple Computer

At 6:12 PM -0500 3/28/05, Brian Jorgage wrote:

I am testing my driver to see if it can run through all the standard
device requests supported by IOUSBDevice->DeviceRequest().  I am
running into problems with "bRequest=GET_DESCRIPTOR".  Return code
keeps coming back as 0xE0004051 - "transaction timed out".  I get the
same result whether I am querying a device descriptor or a
configuration descriptor.

Does anyone know how to fix this ?  Is it an issue w/the device
state ?  Is it a synchronous/asynchronous issue ?  Just as an FYI,
IOUSBDevice->GetConfigurationDescriptor() works fine.

Brian Jorgage


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References:
	>IOUSBDevice->DeviceRequest( ) times out (From: "Brian Jorgage" <email@hidden>)

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