Handle broken union functional descriptors where the master-interface doesn't exist or where its class is of neither Communication or Data type (as required by the specification) by falling back to "combined-interface" probing.

Note that this still allows for handling union descriptors with switched interfaces.

This specifically makes the Whistler radio scanners TRX series devices work with the driver without adding further quirks to the device-id table.

Link: https://lore.kernel.org/r/5f4ca4f8.1c69fb81.a4487.0f5f@mx.google.com Reported-by: Daniel Caujolle-Bert f1rmb.daniel@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Johan Hovold johan@kernel.org --- drivers/usb/class/cdc-acm.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index e28ac640ff9c..f42ade505569 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1240,9 +1240,21 @@ static int acm_probe(struct usb_interface *intf, } } } else { + int class = -1; + data_intf_num = union_header->bSlaveInterface0; control_interface = usb_ifnum_to_if(usb_dev, union_header->bMasterInterface0); data_interface = usb_ifnum_to_if(usb_dev, data_intf_num); + + if (control_interface) + class = control_interface->cur_altsetting->desc.bInterfaceClass; + + if (class != USB_CLASS_COMM && class != USB_CLASS_CDC_DATA) { + dev_dbg(&intf->dev, "Broken union descriptor, assuming single interface\n"); + combined_interfaces = 1; + control_interface = data_interface = intf; + goto look_for_collapsed_interface; + } }

if (!control_interface || !data_interface) {