On 9/20/19 10:51 AM, Ahmad Fatoum wrote: > On 9/20/19 9:58 AM, Ahmad Fatoum wrote: >> barebox currently announces support for ITU V.25ter AT commands, but >> doesn't handle them specially when they arrive. Instead they are passed >> as is to the sole barebox input console, where it may interfere with >> valid user input. >> This is especially annoying as ModemManager probes ttyACM devices that >> announce their AT command support. So even when not using the ttyACM >> device at all, the other UART ports are affected. >> >> Fix this by ceasing to announce USB_CDC_ACM_PROTO_AT_V25TER as function >> protocol. After applying this patch, I can't see any spurious AT or ~x~ >> symbols on the console anymore. > > I've also looked into the possibility of barebox emulating a USB-Serial > port and showing up as a ttyUSB device under Linux. > Apparently the two most popular chips are FTDI's and Prolific's, but both > have taken steps in the past to make their Windows drivers not work with > cloned chips[1][2]. I figured the safest to emulate would be the chip > used safely in these Chinese Arduino Knock-offs because they're so prevalent > and stumbled upon the CH340. Its drivers are mainline for Linux, but for other > platforms, they need to be downloaded manually. > > Seeing that the change to 'fix' barebox ttyACM is just two lines, I settled > for that instead. It might be possible to get rid of the control interface > descriptor altogether, but I don't know whether it would impact the portability > across operating systems, so I've opted for this less invasive patch. Getting rid of the control descriptor makes Linux ttyACM disappear, so I would stick to this patch. > Only tested on Linux v5.2 so far. Tested working as well on Windows 10 Home and macOS Mojave. > > Cheers > Ahmad > > [1]: https://hackaday.com/2016/02/01/ftdi-drivers-break-fake-chips-again/ > [2]: https://www.eevblog.com/forum/reviews/ftdi-driver-kills-fake-ftdi-ft232/msg534439/#msg534439 > >> >> Cc: <bst@xxxxxxxxxxxxxx> >> Cc: <jlu@xxxxxxxxxxxxxx> >> Signed-off-by: Ahmad Fatoum <ahmad@xxxxxx> >> --- >> drivers/usb/gadget/f_acm.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/usb/gadget/f_acm.c b/drivers/usb/gadget/f_acm.c >> index cba59b15859b..42a2b03ad291 100644 >> --- a/drivers/usb/gadget/f_acm.c >> +++ b/drivers/usb/gadget/f_acm.c >> @@ -104,7 +104,7 @@ acm_iad_descriptor = { >> .bInterfaceCount = 2, // control + data >> .bFunctionClass = USB_CLASS_COMM, >> .bFunctionSubClass = USB_CDC_SUBCLASS_ACM, >> - .bFunctionProtocol = USB_CDC_ACM_PROTO_AT_V25TER, >> + .bFunctionProtocol = USB_CDC_PROTO_NONE, >> /* .iFunction = DYNAMIC */ >> }; >> >> @@ -116,7 +116,7 @@ static struct usb_interface_descriptor acm_control_interface_desc = { >> .bNumEndpoints = 1, >> .bInterfaceClass = USB_CLASS_COMM, >> .bInterfaceSubClass = USB_CDC_SUBCLASS_ACM, >> - .bInterfaceProtocol = USB_CDC_ACM_PROTO_AT_V25TER, >> + .bInterfaceProtocol = USB_CDC_PROTO_NONE, >> /* .iInterface = DYNAMIC */ >> }; >> >> > -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
