Bug 1533

causes problems only if PPS has more than one measurable output unit per channel
(like voltage and current).

calling config_list() for channel groups other than only the first channel might result in out-of-bounds access returning garbage.

found with a 4 channel PPS that reports voltage & current per "hardware" channel.

$ sigrok-cli -g 3 --show
reported garbage limits for voltage_target & current_limits.
also SmuView displayed invalid/unusable ranges.

seen with libsigrok master HEAD 2b001a766ad5eadb38ce4025b62b06522b6c52c6.

proposed fix in pull-request https://github.com/sigrokproject/libsigrok/pull/56

i think the problem is caused by using ((struct sr_channel*)cg->channels->data)->index as index into devc->device->channels.
bot scpi-pps/api.c probe_device() can create more channels than there are (struct channel_spec)'s in that array. (comment there says "Create one channel per measurable output unit.") the code there also provides a (struct pps_channel) that includes the "hw_output_idx" which can be used a valid index. this is what i used in that pull-request.