Assign specific plugin for my modem

[Ken CJ Chou]

Hi,
Thank you for replied so quick.

> > I'm now developing my application with ModemManager.
> > I want to add a feature that can directly assign which plugin to use for
> my modem. Instead of using the filter to match appropriate plugin.
> >
>
> I'm not totally sure we'd like to support this, truth be told. The
> different available plugins exist to handle different available
> devices. There should be no device that is "better" managed by a
> different plugin than the one ModemManager thinks is best; at the end
> ModemManager knows what each plugin can do. A different thing would be
> the "generic" plugin that is used as fallback if none other applies
> better; in this case, the solution is to implement a new plugin for
> the new device.
>

Sorry that I didn't say it clearly.
ModemManager is a general tool. One plugin can support many kinds of modems.
I'm afraid that my optimization for one single modem may affects other
modem supported by the plugin.
So I separated it in my current development process.

> This is because I am integrating a modem to a device. And I have
> developed my own plugin for the modem with some optimization.
>
> Did you take an already existing plugin and update it? If so, you
> should keep your own build of ModemManager and just patch the existing
> plugin.
> What does your own plugin do? Is it for a completely new device?
> Please remember that there is no real guarantee that a plugin
> developed out-of-tree will be compatible between different MM
> versions...
>

Can I ask that if I finally have some patches for a plugin.
How can I push them to ModemManager?
Should I send the patch to this mailing-list or a merge request?


> > In this situation, I already know which plugin to use for my modem.
> Currently I use a simple way to achieve. I create a udev tag
> "ID_MM_SUGGESTED_PLUGIN", it's usage is the same as "ID_MM_PHYSDEV_UID".
> Once the device is detected with this tag, I'll set it as the suggested
> plugin.
> > I posted my branch here:
> https://gitlab.freedesktop.org/kenchou0731/ModemManager/-/commit/117c9dcf655007ed57a4a248856df1f4b47bd814
> >
>
> We shouldn't let users select the plugin that way I'm afraid. I don't
> think that's a sane approach for a general use. If you're building
> your own system with always the same kind of modem, why don't you just
> install that single plugin only? I've done that kind of setup for
> several customers and it have worked quite well. Moreover, in MM git
> master and the new 1.14 release soon, you will be able to select at
> configure time which plugins you want to build and install.
>

Yes, to just install the single plugin is a good solution.
I'm glad to hear that  new 1.14 release will have the option to configure
which plugins you want to build and install.
It's helpful for me.


> > Furthermore, I want to do some enhancement for this.
> > My application will sometimes need to reset modem (for changing USB
> configs or changing carrier profile). ModemManager will do the filter for
> finding plugin for every ports of the modem. This procedure took about 1
> second with the debug log enabled. And it may took longer if ModemManager
> supports more and more plugins in the future.
> > I think this procedure can be skipped if I'm sure that which plugin to
> use. And I can reduce the downtime of modem being reset.
>
> I really don't think this is an issue, at least if the plugins are
> correctly setup. The plugin selection has several steps; for plugins
> based on USB like yours, the per-VID/PID filter rule is a simple int
> comparison that is very very quick to decide whether a plugin is
> expected for a device or not. Even if we have 100 plugins, the per-VID
> filter that applies to most of them would make the process very very
> quick. I wouldn't attempt to optimize this very much because it truly
> should be very very quick. For other filter decisions it may take some
> more time, e.g. if it needs to do AT vendor probing for RS232 modems,
> but that is totally understandable because there is no better option.
>

Understand. I don't think this should be an issue for ModemManager.
I'm just thinking that how can I reduce the downtime for modem during reset.
And I'll try it with only install the single plugin. Thank you!

Best regards,
Ken
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