On 12.06.2012 20:23, Daniel Mack wrote:
TEAC's UD-H01 (and probably other devices) have a gap in the interface number allocation of their descriptors:
I now got a report from Sergio Tabanelli who tried this patch on real hardware, and he confirmed the fix. I added some more people to the patch description and copied stable@ as well.
Greg, can can this go through your tree?
Daniel
Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 220 bNumInterfaces 3 [...] Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 [...] Interface Association: bLength 8 bDescriptorType 11 bFirstInterface 2 bInterfaceCount 2 bFunctionClass 1 Audio bFunctionSubClass 0 bFunctionProtocol 32 iFunction 4 Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 2 bAlternateSetting 0 [...]
Once a configuration is selected, usb_set_configuration() walks the known interfaces of a given configuration and calls find_iad() on each of them to set the interface association pointer the interface is included in.
The problem here is that the loop variable is taken for the interface number in the comparison logic that gathers the association. Which is fine as long as the descriptors are sane.
In the case above, however, the logic gets out of sync and the interface association fields of all interfaces beyond the interface number gap are wrong.
Fix this by passing the interface's bInterfaceNumber to find_iad() instead.
Signed-off-by: Daniel Mack zonque@gmail.com Reported-by: bEN ml_all@circa.be Reported-by: Ivan Perrone ivanperrone@hotmail.com
This patch has been tested on a virtual USB device emulated in QEMU. I'm still waiting for test results based on real hardware, but the bug is rather obvious is and the fix really simple.
Daniel