Re: Access to SIM card when Modem is not "Powered"

[Denis Kenzior <denkenz@gmail.com>]

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Hi Pekka,

> >> I'm trying to
> >> 1) load atoms only after when isimodem is up and running and reset the
> >> state of the isimodem atoms in case the isimodem reboots (or user
> >> turns off a Nokia handset connected via USB)
> >> 2) have asyncronous probe and remove
> >> 3) separate rf state and availablity of the atoms, especially the SIM
> >> atoms.
> >>
> >> With the current enable/disable/ofono_modem_set_powered, I can do 1)
> >> or 2), but not both. I can not do 3 at all.
> >
> > non of these should be solved via the D-Bus at all. Really this is
> > internal modem specific details. You are approaching this wrongly.
> 
> 1) and 2) are already done through D-Bus, only thing is missing is
> oFono core properly supporting transitions between Powered false and
> true.

So I just checked again, and we remove all atoms when turning off (even if off 
subsequently fails).  So I really don't see a need to expose the transition 
(e.g. going up, going down) as a property.  How do you want to use this 
information?

> 
> > 1) If the modem reboots, then handle this inside the isimodem plugin of
> > oFono.
> 
> It is already handled fine in core. isidriver calls
> ofono_modem_set_powered(false) when it detects that isimodem reboots.
> When modem is back in business, it calls
> ofono_modem_set_powered(true).
> 
> Is there a particular reason why I should reinvent the wheel?
> 

From your earlier posts it wasn't clear that you're happy with how this works.  
I perceived that there was some issue... 

> >No reason to involve userspace here. If the handset gets turned
> > off, then the modem object just goes away.
> 
> What is the difference between modem object not being there at all and
> modem object being there, but with Powered=false?

Think of it conceptually as a USB device being in an off state but still on the 
bus.  You still know the device is attached, even if it is of limited use.  
Remember that we use this to populate remote bluetooth devices, modems 
configured via modemconf and udev/netlink.  This conveys presence and potential 
usability.

> 
> With the current ofono core, removing the object path will also remove
> the config information.

What are you using the config information for?  It is possible that we should 
implement ofono_modem_unregister that would keep around the non-driver bits of 
the modem object.  So far I have not done so because I saw no need...

> 
> > 2) What do you mean by this. They are asynchronous.
> 
> Not in the master branch. enable() and disable() are async, probe()
> and remove() are sync.

probe and remove are sync for a reason, the core is going to become extremely 
complicated otherwise.  Been there and done that, so you better have a very 
good reason for wanting this.

> 
> How the driver knows if the disable() is called because someone just
> tried to set Powered=false or if ofonod is terminating? In first case,
> I just want modem to go standby (and flush the atoms) and keep the SIM
> warmed up and ready, in the second case, driver should ask modem to do
> proper power off and then does all the required jazz with the gpio
> lines. It would be help much if disable() would indicate if "soft"
> poweroff  or "hard" poweroff is required; likewise

This can be added, but the question is are you sure you need it?  None of the 
other hardware we have would benefit from this functionality at all.  This 
immediately raises the question of usefulness.  Are you sure this isn't better 
accomplished by a specific plugin for your system as discussed elsewhere in 
this thread?

> ofono_modem_set_powered() could take enum with transitional states
> (powering_on, powered_on, powering_off, powered_off + perhaps
> something like powered_standby). If you don't feel like doing it, I'm
> happy to contribute.

Again, usecase please.  How are you going to use this information?

> 
> > 3) I don't understand this. We have pre-sim and post-sim functionality.
> > If you RFKILL a radio it would be same as removing its object path. Or
> > do you wanna access the SIM card while RFKILLed. What is that good for?
> 
> Nobody wants to re-enter the pin code if they exit flight mode. It
> should be possible to spool SMSs while the device is in flight mode.
> 
> Is there any good reason to keep SIM offlimits?

Please note that if your enable/disable behavior only shuts the rx/tx circuits 
then repeating PIN entry won't be a problem.  And I already commented on this 
elsewhere in the thread.

All I ask is that before we start adding tons of properties we first make sure 
the user can actually use them intelligently,  that there is an actual (not 
just perceived) use case.

Regards,
-Denis