[PATCH 09/10] libbsd.txt: Describe current state of WLAN.

[Christian Mauderer]

Am 11.11.2017 um 05:14 schrieb Chris Johns:
> On 10/11/2017 17:59, Christian Mauderer wrote:
>>
>> I took a quick glance to find out the behaviour on FreeBSD: It supports
>> hot-plugging. If I for example add a
>>
>>   wlans_rtwn0="wlan7"
>>   ifconfig_wlan7="DHCP"
>>
>> to rc.conf a RTL8188 USB WiFi dongle is created as wlan7. I'll add that
>> pice of information to the ticket. I think further investigation is
>> necessary which services are involved into that.
> 
> This makes sense and thank you.
> 
>> But that will have to wait till there is time for that part.
> 
> Yes.
> 
>>
>> I meant that we could parse the rc.conf on the first pass and then put
>> the relevant information (rtwn0 as wlan7) into for example a linked
>> list. That list can then be used in the hot-plug-events. With that, it
>> wouldn't be necessary to do a lot of string parsing on every device
>> detection.
> 
> I think the overhead of parsing will be small compared to the act of the device
> being added to a system. This sort of code is not time critical. It would be
> nice to be able to edit rc.conf reinsert the device and see what happens.

The problem with "edit rc.conf" is that (as far as I understood that
interface) we have two possible sources:

1. from a string: rtems_bsd_run_rc_conf_script
2. from a file: rtems_bsd_run_rc_conf and rtems_bsd_run_etc_rc_conf

So we would have to remember the last source and parse that. Can we be
sure that the string is always there or would it be necessary to
duplicate it? The "const char* text" should in theory guarantee that it
won't change, right?

> 
>>
>> But that is something that would have to be discussed as soon as someone
>> want's to start an implementation.
>>
> 
> Yes I agree. Do you think hot-plug support is a suitable GSoC project for next year?

I would expect that it is quite a lot of initial investigation to find
out how to do that (for example: finding out how to get events for new
devices). But if a student is interested in it, I would say it should be
OK as a project.

But note that I would see the two tickets quite separate in that case
and could even be separate projects.

The first one would be to find some events from newly created devices
and do something depending on that events (rc.conf parsing and creating
wlanX interfaces).

The second one would be to make dhcpcd hooks useable for RTEMS and then
do something with them like calling wpa_supplicant.

I think both shouldn't be too hard in regard to the coding. But they
might need some deeper understanding of the libbsd or dhcpcd which could
be hard for someone who isn't used to read bigger amounts of source code
- especially if it has that many layers of abstraction like FreeBSD code.

Regards

Christian

> 
> Thank you for investigating this.
> 
> Chris
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