[Bug 1958224] Re: brltty claiming cp210x devices on 22.04

[Walter]

Not sure what is fixed with 6.4-4ubuntu3.

I removed/purged brltty, rebooted (just to make sure) and checked the
/dev/ttyUSB0 availability:

[   89.311770] usb 3-3: new full-speed USB device number 4 using xhci_hcd
[   89.529433] usb 3-3: New USB device found, idVendor=1a86, idProduct=7523, bcdDevice= 2.64
[   89.529439] usb 3-3: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[   89.529440] usb 3-3: Product: USB Serial
[   90.069647] usbcore: registered new interface driver usbserial_generic
[   90.069654] usbserial: USB Serial support registered for generic
[   90.074280] usbcore: registered new interface driver ch341
[   90.074290] usbserial: USB Serial support registered for ch341-uart
[   90.074300] ch341 3-3:1.0: ch341-uart converter detected
[   90.074810] usb 3-3: ch341-uart converter now attached to ttyUSB0
[   93.183733] usb 3-3: USB disconnect, device number 4
[   93.184054] ch341-uart ttyUSB0: ch341-uart converter now disconnected from ttyUSB0
[   93.184072] ch341 3-3:1.0: device disconnected


That works. After installing brltty and retrying, we see that /dev/ttyUSB0 is immediately stolen.

[  130.375473] usb 3-3: new full-speed USB device number 5 using xhci_hcd
[  130.593243] usb 3-3: New USB device found, idVendor=1a86, idProduct=7523, bcdDevice= 2.64
[  130.593249] usb 3-3: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[  130.593250] usb 3-3: Product: USB Serial
[  130.595110] ch341 3-3:1.0: ch341-uart converter detected
[  130.595546] usb 3-3: ch341-uart converter now attached to ttyUSB0
[  131.168883] input: PC Speaker as /devices/platform/pcspkr/input/input17
[  131.677420] input: BRLTTY 6.4 Linux Screen Driver Keyboard as /devices/virtual/input/input18
[  131.797698] usb 3-3: usbfs: interface 0 claimed by ch341 while 'brltty' sets config #1
[  131.798107] ch341-uart ttyUSB0: ch341-uart converter now disconnected from ttyUSB0
[  131.798115] ch341 3-3:1.0: device disconnected


Here's the lsusb output:

# lsusb 
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 002: ID 27c6:609c Shenzhen Goodix Technology Co.,Ltd. Goodix USB2.0 MISC
Bus 003 Device 005: ID 1a86:7523 QinHeng Electronics CH340 serial converter
Bus 003 Device 003: ID 8087:0032 Intel Corp. AX210 Bluetooth
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub


Apparently, I'm not using a CP210x but a CH340. It suffers from the same problem though.

Having said that, I agree with Steve [~vorlon]:

> That represents a CRITICAL regression for the users in question.
> It effectively bricks their machine and requires the user to rely
> on a sighted person (who is also Ubuntu-knowledgeable) to get it
> working again.

We can just purge brltty and be done with it. So it's clearly the lesser
of two evils right now.

Walter

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Title:
  brltty claiming cp210x devices on 22.04

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