crypto: rename hmac_sha256() to rtw_hmac_sha256() to fix build on Linux 7.0

[s-b-repo]

Problem

dwa-x1850 HEAD does not build on Linux 7.0:

core/crypto/sha256.h:16:5: error: conflicting types for 'hmac_sha256'; have
  'int(const u8 *, size_t,  const u8 *, size_t,  u8 *)'
core/crypto/sha256.c:100:5: error: conflicting types for 'hmac_sha256'; have
  'int(const u8 *, size_t,  const u8 *, size_t,  u8 *)'
make[4]: *** [scripts/Makefile.build:289: core/crypto/sha256.o] Error 1

Eric Biggers' lib/crypto SHA-256 series made HMAC a first-class part of the
SHA-256 library, adding to include/crypto/sha2.h:

void hmac_sha256(const struct hmac_sha256_key *key, const void *data,
                 size_t data_len, u8 out[SHA256_DIGEST_SIZE]);

That collides with the driver's wpa_supplicant-derived function of the same name
and incompatible signature:

int hmac_sha256(const u8 *key, size_t key_len, const u8 *data,
                size_t data_len, u8 *mac);

Both headers land in the same translation unit, so the declarations conflict.

Fix

Rename the driver's function to rtw_hmac_sha256().

grep -rnw hmac_sha256 finds exactly three occurrences — a kernel-doc comment,
the definition, and the declaration — and zero call sites. Only
hmac_sha256_vector() is actually used, by core/crypto/sha256-prf.c. The rename
is therefore behaviour-neutral, and because the symbol is driver-internal it needs
no LINUX_VERSION_CODE guard — it is safe on every kernel version.

Reproduction

git clone -b dwa-x1850 https://github.com/natimerry/rtl8852au
cd rtl8852au
make -j$(nproc) KVER=$(uname -r)     # on a 7.0 kernel

Verification

Built on Arch Linux, kernel 7.0.14-arch1-1 (x86_64), gcc 16.1.1 20260625:

Tree	Result
dwa-x1850 HEAD, unmodified	exit status 2, no module produced
dwa-x1850 HEAD + this commit	exit status 0, zero errors, 8852au.ko built

modinfo on the resulting module reports vermagic: 7.0.14-arch1-1 SMP preempt mod_unload.

This also fixes the AUR rtl8852au-dkms-git package, which currently fails to
build on Arch for the same reason.

Unrelated observation: radio_id is not version-gated

Not part of this PR, just something I hit while bisecting. The kernel 6.17
radio_id fix already in dwa-x1850 is applied unconditionally:

static int cfg80211_rtw_set_wiphy_params(struct wiphy *wiphy, int radio_id, u32 changed)

struct cfg80211_ops only gained that parameter in 6.17, so as written the tree
no longer builds on older kernels. If you want to keep those working, the three
sites (cfg80211_rtw_set_wiphy_params, cfg80211_rtw_set_txpower,
cfg80211_rtw_get_txpower) want:

#if (LINUX_VERSION_CODE >= KERNEL_VERSION(6, 17, 0))
	int radio_id,
#endif

Happy to send that as a separate PR if it would be useful.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Xh5tbTQAWbek2feXD2uhaZ