Bug#1012152: firmware-amd-graphics: All firmware are included in initrd even in dep mode

[Adrien CLERC <bugs-debian@antipoul.fr>]

    Package: firmware-amd-graphics
    Version: 20210818-1
    Severity: minor
    
    Dear Maintainer,
    
    Since the integration of built-in drivers in initramfs-tools (see
https://salsa.debian.org/kernel-team/initramfs-tools/-/merge_requests/35),
    firmware files are also included with the corresponding kernel
    module.
    I don't know why, but it only hits my system (AMD Ryzen PRO 4750G)
    since May,
    7th with Linux 5.17.0. Before that, amdgpu was NOT included in the
    initrd.
    
    Now that it's included, it brings all firmwares for all AMD graphics
    card,
    making the initrd from 11MB to 38MB. This has 3 drawbacks for me:
    1. Building initrd is longer, so updates that trigger this take
    longer
    2. Booting is also longer. It happens that even 1s faster matters to
    me ;)
    3. My /boot partition is too small (182MB, hard to increase due to
    LUKS
    partition after that), and I am hit by "no space left on device"
    (see
    https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=972396)
    
    But on top of this, I know that I don't need all those firmwares. In
    fact,
    amdgpu kindly reports which firmwares are loaded at start, so I made
    a hook
    that removes everything but the needed files (see attached).
    
    Now for some benchmarks. First, initrd extraction.
    
    hyperfine -N --warmup 3 "lsinitramfs -l
    ./initrd.img-5.17.0-3-amd64.nohook"
    "lsinitramfs -l ./initrd.img-5.17.0-3-amd64.hook"
    Benchmark 1: lsinitramfs -l ./initrd.img-5.17.0-3-amd64.nohook
    Time (mean ± σ): 130.7 ms ± 4.4 ms [User: 69.4 ms, System: 100.3 ms]
    Range (min … max): 125.2 ms … 146.1 ms 22 runs
    
    Benchmark 2: lsinitramfs -l ./initrd.img-5.17.0-3-amd64.hook
    Time (mean ± σ): 68.8 ms ± 1.2 ms [User: 34.9 ms, System: 53.5 ms]
    Range (min … max): 66.9 ms … 72.2 ms 42 runs
    
    Summary
    'lsinitramfs -l ./initrd.img-5.17.0-3-amd64.hook' ran
    1.90 ± 0.07 times faster than 'lsinitramfs -l
    ./initrd.img-5.17.0-3-amd64.nohook'
    
    So extracting initramfs is 90% faster.
    
    Updating the initrd is less obvious. I use LZ4 for compression on my
    system,
    with MODULES=dep
    
    hyperfine "update-initramfs -u"
    Benchmark 1: update-initramfs -u
    Time (mean ± σ): 3.379 s ± 0.033 s [User: 2.856 s, System: 0.563 s]
    Range (min … max): 3.341 s … 3.456 s 10 runs
    
    Without the hook
    
    hyperfine "update-initramfs -u"
    Benchmark 1: update-initramfs -u
    Time (mean ± σ): 4.175 s ± 0.048 s [User: 3.436 s, System: 0.738 s]
    Range (min … max): 4.118 s … 4.261 s 10 runs
    
    It is only 20% faster.
    
    In the end, I am asking for code review in the hook I wrote. I know
    I missed
    some cases, because I am not used this part of the system.
    
    
    -- System Information:
    Debian Release: bookworm/sid
    APT prefers unstable-debug
    APT policy: (500, 'unstable-debug'), (500, 'unstable'), (1,
    'experimental')
    Architecture: amd64 (x86_64)
    
    Kernel: Linux 5.17.0-3-amd64 (SMP w/16 CPU threads; PREEMPT)
    Locale: LANG=fr_FR.UTF-8, LC_CTYPE=fr_FR.UTF-8 (charmap=UTF-8),
    LANGUAGE not set
    Shell: /bin/sh linked to /bin/dash
    Init: systemd (via /run/systemd/system)
    LSM: AppArmor: enabled
    
    firmware-amd-graphics depends on no packages.
    
    firmware-amd-graphics recommends no packages.
    
    Versions of packages firmware-amd-graphics suggests:
    ii initramfs-tools 0.141
    
    -- no debconf information

#!/bin/sh

PREREQ=""

prereqs()
{
    echo "$PREREQ"
}

case "$1" in
    prereqs)
        prereqs
        exit 0
        ;;
esac

. /usr/share/initramfs-tools/hook-functions

FIRMWARES=$(dmesg | grep -oP 'amdgpu.*direct-loading firmware amdgpu/\K(.*bin)$')

if [ -z "$FIRMWARES" ]; then
	exit 0
fi

echo "Removing all AMDGPU firware except $(echo $FIRMWARES | xargs echo)"

rm "$DESTDIR/usr/lib/firmware/amdgpu"/*
for firmware in $FIRMWARES; do
	copy_file firmware "/lib/firmware/amdgpu/${firmware}"
done