Notify downstream consumers before build interface changes

[jetm]

Track any planned breaking changes to the build interface (make download, make sources, make install, make check-version) so downstream consumers like samutoljamo/bazzite-mt7927 get advance notice.

The current interface has been stable since v2.9. If it needs to change, open a comment here before the release.

cc @samutoljamo - subscribe to this issue for notifications. Ref: samutoljamo/bazzite-mt7927#18

[jetm]

Heads up for downstream packagers/consumers: v2.11 has two build-interface changes that affect kernels < 7.0.

Kernel tarball bumped to 7.0

_mt76_kver in the PKGBUILD (and the equivalent KVER in Makefile) moved from 6.19.10 to 7.0. The package now pulls mt76/btusb/btmtk sources from the linux-7.0 tarball on kernel.org.

Rationale: kernel 7.0 exports hci_discovery_active() (commit 97eb023cd161) which btusb uses. Pulling from an older tarball would require either dropping the symbol reference (lossy) or backporting the export. Bumping the tarball keeps us aligned with current upstream BT.

Two new compat patches for kernels < 7.0

Kernel 7.0 introduced new allocator helpers that the 7.0 tarball uses internally. When building for kernels < 7.0 the allocator helpers are not available, so we apply compat patches that restore the old kmalloc(sizeof(*x), GFP_KERNEL) / kzalloc(struct_size(...)) idiom.

Added:

• mt6639-bt-compat-kmalloc_obj-for-pre-7.0-kernels.patch - fixes kmalloc_obj / kzalloc_obj in btusb.c (3 sites) and btmtk.c (1 site), plus drops the hci_discovery_active() call added in 7.0
• mt7927-wifi-compat-kzalloc_flex-for-pre-7.0-kernels.patch - fixes kzalloc_flex in mt76/agg-rx.c

These patches are named *-compat-* (non-numeric prefix) so our regeneration scripts do not treat them as part of the numbered patch set.

Background references:

• kmalloc_obj introduced by commit 2932ba8d9c99
• kzalloc_flex introduced by commit e4c8b46b924e
• Treewide conversion 69050f8d6d07 (Kees Cook)

Makefile impact

The patch-apply loop in Makefile was updated to pick up both numbered and *-compat-* patches:

for p in $(TOPDIR)mt6639-bt-[0-9]*.patch $(TOPDIR)mt6639-bt-compat-*.patch; do ...

If your downstream has its own Makefile or apply loop, make sure both globs are covered.

Also gen-dkms-patches.sh was narrowed from mt7927-wifi-*.patch to mt7927-wifi-[0-9]*.patch on the cleanup step so the compat patch survives patch regeneration.

Testing suggestion

Build on the oldest kernel you support (compat patches apply) and on kernel 7.0 (compat patches are no-ops in practice because upstream has the conversions). If you've pinned an older mt76 snapshot, review the compat patches against your snapshot's code to confirm the hunks still target the right lines.

Ping me on this issue if a hunk conflicts against your downstream.