[systemd-devel] WebUSB

[Christer Weinigel]

On 2017-01-10 19:55, Lars Knudsen wrote:
> On Tue, Jan 10, 2017 at 7:08 PM, Dan Williams <dcbw at redhat.com
> <mailto:dcbw at redhat.com>> wrote:
>     And we're quite happy to keep blacklisting specific VID/PID combos we
>     know are not modems. Another possible solution is to greylist devices
>     that happen to have webusb descriptors, such that they won't get auto-
>     probed, but could be probed on-demand via D-Bus.  But I'd rather that
>     happen via udev rules than MM trying to walk USB device attributes and
>     parsing webusb descriptors.
> 
> Actually, that sounds like a very good compromise.  I remember my own
> struggles 3-4 years ago when I had to get a device working properly on
> ChromeOS and Ubuntu, where the firmware had to handle that the first ~16
> seconds it would *sometimes* get sent strange AT commands (the probing)
> all while the system thought it could already start speaking with the
> device over e.g. chrome.serial.  Eventually you (modemmanager) were kind
> enough to get our VID/PID listed and ChromeOS was quick to pick it up
> (~5-6 months to get in stable) and ubuntu so kind to upgrade to the
> version of modemmanager including our blacklisting approx 2.5 years
> later (sigh) ;)

Weird question: should modem manager really autoprobe _every_ serial
device nowdays?  99% of the devices I connect to my laptop are not
modems.  They are serial ports on development platforms, RS485
interfaces, Arduinos with a FTDI, CP210x or CH341 USB-UART bridge, and
so on.  Modems with a physical serial port are almost nonexistent today.
 For me it's a pain in the back to have to update the blacklist of
things modem manger shouldn't touch.

Wouldn't it be better to whitelist known ḿodems and have modem manager
ignore everything else?  Devices which are so new that modem manager
don't know about them can be configured manually.

At least to me that seems like a much more sane default.

  /Christer