EG25 integration patches in plasma mobile

[Bjørn Mork]

Aleksander Morgado <aleksander at aleksander.es> writes:

> The people at KDE are working on some patches to better integrate the
> EG25 under suspend/resume events; they're changing not only power
> related sysfs attributes, but also patching certain parts of the
> kernel drivers, including the cdc-wdm driver.
>
> https://invent.kde.org/teams/plasma-mobile/issues/-/issues/3
>
> Any chance you could take a look at that merge request and provide
> your own comments on the issue?

The kernel stuff should obviously be reviewed by kernel experts.  Not me
:-)

Anyway, this looks like an attempt to work around a host controller issue
by making the device driver ignore part of the spec.  It might work for
this specific case where the USB device has retained its state, IIUC.
But that is usually not the case with USB modmes.

The reset_resume logic and background is documented in
Documentation/driver-api/usb/persist.rst

The solution works fine if both system and device retains state. But
modems don't do that if they lose power during suspend.  I believe we
have to trust the host controller, and if it says reset then we have to
reset.


Bjørn