New ini-file parser breaks hm2_eth config on master

[hdiethelm]

The reason is probably this PR:
#3921

It took me some time and bisecting to figure out the reason. With added some debug printf's:
Before:
rtapi_app load hm2_eth board_ip=192.168.1.121 config="num_encoders=0 num_pwmgens=1 num_stepgens=4"
After:
rtapi_app load hm2_eth board_ip=192.168.1.121 config=num_encoders=0 num_pwmgens=1 num_stepgens=4
Note the missing "

The error message is quite usless:

hm2: loading Mesa HostMot2 driver version 0.15
./hm2-stepper-eth.hal:38: waitpid failed /home/hannes/linuxcnc-src/bin/rtapi_app hm2_eth
./hm2-stepper-eth.hal:38: /home/hannes/linuxcnc-src/bin/rtapi_app exited without becoming ready
./hm2-stepper-eth.hal:38: insmod for hm2_eth failed, returned -1

Relevant section of the ini file:

[HOSTMOT2]
DRIVER=hm2_eth
BOARD_IP=192.168.1.121
BOARD=7i96s
CONFIG="num_encoders=0 num_pwmgens=1 num_stepgens=4"

And the hal file:

# load low-level driver
loadrt [HOSTMOT2](DRIVER) board_ip=[HOSTMOT2](BOARD_IP) config=[HOSTMOT2](CONFIG)

@BsAtHome I can work around it by just placing the config directly in the hal file for now.

[BsAtHome]

The "breaks..." is more like "I probably intentionally broke..." ;-)

The problem is that double quotes no longer are a literal part of a value but are now interpreted. This is, of course, unfortunate for existing configs. But is does add consistency for the future.

The simple fix is enclose the double quoted string in single quotes in the INI-file entry to:

[HOSTMOT2]
...
CONFIG='"num_encoders=0 num_pwmgens=1 num_stepgens=4"'
...

Alternative is to escape the double quotes in a double quoted string:

[HOSTMOT2]
...
CONFIG="\"num_encoders=0 num_pwmgens=1 num_stepgens=4\""
...

However, I'd prefer using a single quoted string with embedded double quotes.

[hdiethelm]

Thanks for the info. So more like a breaking change needing users to update their config together with hm2_eth not generating useful error messages.

There are a lot of examples and might be also doc that need updating in this case. Just one example that is broken now: configs/by_interface/mesa/hm2-stepper/4i68.ini

It would make sense to add some checks and give a proper error in hm2_eth, it took me some time to resolve it and others will have the same issue for sure.

[BsAtHome]

Already going through all configs' ini-files.

It was unknown to be breaking this particular use... However, there was anticipated some fallout.

[hdiethelm]

Ok, all fine.

This parameter parsing also happens in uspace_rtapi_app.cc. It looks like the warning about unknown parameters is broken on master. On 2.9, I have a warning when I add a parameter that is not used.

I can look into that but only after #3919 got merged.

[BsAtHome]

Fix in #3947 for in-tree configs.

[hdiethelm]

That was fast! Meanwhile, I traced the missing error message. There is one, it is just not shown in master: #3948