Re: [PATCH] USB: cdc-acm: Add quirks for Yoga Book 9 14IAH10 INGENIC touchscreen

[Oliver Neukum <oneukum@suse.com>]

On 02.04.26 20:29, Dave Carey wrote:
> The Lenovo Yoga Book 9 14IAH10 (83KJ) has a composite USB device
> (17EF:6161) that controls both touchscreens via a CDC ACM interface.
> Interface 0 is a standard CDC ACM control interface, but interface 1
> (the data interface) incorrectly declares vendor-specific class (0xFF)
> instead of USB_CLASS_CDC_DATA. cdc-acm rejects the device at probe with
> -EINVAL, leaving interface 0 unbound and EP 0x82 never polled.
> 
> With no consumer polling EP 0x82, the firmware's watchdog fires every
> ~20 seconds and resets the USB bus, producing a continuous disconnect/
> reconnect loop that prevents the touchscreens from ever initialising.
> 
> Add two new quirk flags:
> 
> VENDOR_CLASS_DATA_IFACE: Bypasses the bInterfaceClass check in
> acm_probe() that would otherwise reject the vendor-class data
> interface with -EINVAL.
> 
> ALWAYS_POLL_CTRL: Submits the notification URB at probe() rather than
> waiting for a TTY open. This keeps EP 0x82 polled at all times,
> permanently suppressing the firmware watchdog. The URB is resubmitted
> after port_shutdown() and on system resume. SET_CONTROL_LINE_STATE
> (DTR|RTS) is sent at probe and after port_shutdown() to complete
> firmware handshake.
> 
> Note: the firmware performs exactly 4 USB connect/disconnect cycles
> (~19 s each) on every cold boot before stabilising. This is a fixed
> firmware property; touch is available ~75-80 s after power-on.
> 
> Signed-off-by: Dave Carey <carvsdriver@gmail.com>
> Tested-by: Dave Carey <carvsdriver@gmail.com>
Acked-by: Oliver Neukum <oneukum@suse.com>