[systemd-devel] systemd version debus call changed

[Timothée Ravier]

On 03/03/2014 14:28, Àlex Fiestas wrote:
> On Friday 28 February 2014 02:28:20 Lennart Poettering wrote:
>> They should just invoke the methods. If they get
>> org.freedesktop.DBus.Error.UnknownMethod,
>> org.freedesktop.DBus.Error.UnknownObject or
>> org.freedesktop.DBus.Error.UnknownInterface back they should assume that
>> logind is too old and doesn't support the call. (Actually, to make this
>> really robust, they should just treat any error like that).
>>
>> Check for features by trying to make use of them. Don't check for
>> version numbers.
> The problem was that long ago logind supported suspend (methods were in the 
> bus) but they did not work, at least not for opensuse so that work around was 
> added.
> 
> This code will certainly die in the near future.

I'm working on fixing this for KDE
(https://git.reviewboard.kde.org/r/116527/). But now that I've looked at
it little bit closer I think I may understand why they did version checks:

As far as I understand, between v183 (d889a2069a87e4617b32dd) and v198
(314b4b0a68d9ab35de98192), PrepareForSleep signal is sent before
suspending, but no signal is sent on resume, thus one must use upower to
get this info; From v198 and onward, PrepareForSleep signal is also sent
on resume, thus no need for upower anymore.

Am I correct here? Did I miss something? Are there are any other
solutions than checking for the version number to know if
PrepareForSleep will be sent on resume? Should we just give up trying to
support versions of systemd older than 198 (for systemd-based systems)?

-- 
Timothée Ravier