Bug#991587: hw-detect: check-missing-firmware can be a tad aggressive

[Cyril Brulebois <kibi@debian.org>]

Package: hw-detect
Version: 1.146
Severity: important
X-Debbugs-Cc: debian-cd@lists.debian.org

I hadn't seen the following when test-installing in loops, since I was
using a netboot-gtk image, but this can be seen with a regular netinst
image produced by debian-cd, since the d-i image used there is slightly
different. I fear this is going to be a rather common annoyance, so I'd
like to get that fixed before the Bullseye release (either in D-I
Bullseye RC3 or in the final D-I release).


On this Dell G3, right after selecting locale settings, cdrom-detect
kicks in and tries to find the installation image to load. Doing so, it
calls hw-detect with this (two occurrences):

    hw-detect cdrom-detect/detect_progress_title || true

which iso-scan can also do (one occurrence):

    hw-detect iso-scan/detect_progress_title || true

At the bottom of hw-detect, there's a check-missing-firmware call, which
can trigger errors and prompts about irrelevant firmware files, e.g.:

    intel/sof/sof-cml.ri

(which is about sound support, see firmware-sof-signed.)


While I'm not entirely certain about use-cases around iso-scan, I would
think cdrom-detect should be one of the very few first things to happen
on a system, and that raising errors because of missing firmware files
at this stage wouldn't help: even a firmware-enabled image wouldn't be
mounted and firmware packages wouldn't be available (later, they show up
at /cdrom/firmware).

Therefore, I'm proposing:

 1. Implement support for an environment variable in hw-detect, that
    would disable the check-missing-firmware call.
 2. Set this variable for both hw-detect calls in cdrom-detect's
    postinst. [This should fix the problem I'm seeing.]
 3. Set this variable for the hw-detect call in iso-scan's postinst.
    [Optional, I'm not sure what people are doing before iso-scan kicks
    in; maybe some firmware-holding block devices could be available at
    this stage, so letting the missing firmware detection in place might
    make sense in this case.]


For the avoidance of doubt, hw-detect is called in many places, later
for networking devices and for disks; those are much more likely to
require some firmware files to be available…


Cheers,
-- 
Cyril Brulebois (kibi@debian.org)            <https://debamax.com/>
D-I release manager -- Release team member -- Freelance Consultant