Re: [PATCH 1/1] rfkill: add the GPS radio type

[Marcel Holtmann <marcel@holtmann.org>]

Hi Tomas,

> >> > > we don't have a GPS subsystem, but even without it, I think this is a
> >> > > good thing to have.
> >> >
> >> > GPS devices are usually serial devices.
> >>
> >> Yeah, this is interesting -- do we want something like /dev/urfkill
> >> (cf. /dev/uinput), so that gpsd or whatever is controlling the GPS (same
> >> applies for 3G) can be controlled with rfkill?
> >
> > on one hand I think urfkill might be needed, on the other hand I think
> > we should not do it at all. Currently I would think it is better to
> > force the RFKILL integration in the kernel so that we have proper
> > subsystem integration, or platform RFKILL switches or in cases like GPS
> > and WWAN/3G it will be driver integration. For 3G we already have the
> > hso.ko driver which has a killswitch and we just need to fix the other
> > ones. I am actually looking into it, if this is possible without an AT
> > parser inside the kernel.
> 
> >
> > So the GPS world is evolving right now and that everybody implements
> > them as kernel-tty-passthrough pseudo driver and then a binary only
> > daemon and then gpsd/gypsy on top of it will only survive for certain
> > amount of time. The binary component will not get wide acceptance. And
> > even if the binary only userspace component stays, we might still need a
> > proper GPS subsystem since using TTY as pure transport is holding us
> > back. Could be that AF_GPS would have been a way better choice. This
> > will sort itself out over time.
> >
> 
> BT also fails to the same category. BT driver also just servers as HCI
> transport layer.
> Current implementation of closing device driver is not sufficient to
> really bring the device to rfkill mode. My point is from multi com
> devices. What vendor implements are proprietary HCI commands that
> brings device to rfkill mode, there is no standard. So in general you
> would need HCI parser similar to AT parser or NMEA GPS parser  The
> rfkill event is transferred inside the transport not visible to device
> driver.
> In other words RFKILL is happening between device and application w/o
> kernel intervention. This is a problem since usually user application
> and kernel has to be somehow notified.

I have no idea what you are talking about here. The Bluetooth RFKILL
does exactly the right thing. The driver gets the down callback and is
responsible to bring the device down. It is expected that the radio will
be brought down at that point.

> Frankly I still don't understand what flow of how /dev/uevent is
> helpful here. Who is notifying whom about rfkill event.

Starting with 2.6.31 kernel we are using /dev/rfkill for notification
about RFKILL state changes. Previously it was done via uevents, but that
was more broken than helpful.

Regards

Marcel