wifi: cfg80211: simplify cfg80211_chandef_compatible()

Simplify cfg80211_chandef_compatible() a bit by switching
c1 and c2 around so that c1 is always the narrower one
(once they're not identical or narrow/S1G). Then we can
just check the various primary channels and exit with the
wider one (c2), or NULL.

Also refactor the primary 40/80/160 function to not have
all the calculations hard-coded, and use a wrapper around
it to check primary 40/80/160 compatibility.

While at it, add some kunit tests for this functionality.

Also expose the new cfg80211_chandef_primary_freq() to
drivers, mac80211 will use it.

Link: https://msgid.link/20240129194108.be3e6eccaba3.I8399c2ff1435d7378e5837794cb5aa6dd2ee1416@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

2 files changed, 183 insertions, 1 deletions

diff --git a/net/wireless/tests/Makefile b/net/wireless/tests/Makefile
index 1f6622fcb758..c364e63b508e 100644
--- a/net/wireless/tests/Makefile
+++ b/net/wireless/tests/Makefile
@@ -1,3 +1,3 @@
-cfg80211-tests-y += module.o fragmentation.o scan.o util.o
+cfg80211-tests-y += module.o fragmentation.o scan.o util.o chan.o
 
 obj-$(CONFIG_CFG80211_KUNIT_TEST) += cfg80211-tests.o
diff --git a/net/wireless/tests/chan.c b/net/wireless/tests/chan.c
new file mode 100644
index 000000000000..b9e7a27e43cb
--- /dev/null
+++ b/net/wireless/tests/chan.c
@@ -0,0 +1,182 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KUnit tests for channel helper functions
+ *
+ * Copyright (C) 2023 Intel Corporation
+ */
+#include <net/cfg80211.h>
+#include <kunit/test.h>
+
+MODULE_IMPORT_NS(EXPORTED_FOR_KUNIT_TESTING);
+
+static struct ieee80211_channel chan_6ghz_1 = {
+	.band = NL80211_BAND_6GHZ,
+	.center_freq = 5955,
+};
+
+static struct ieee80211_channel chan_6ghz_5 = {
+	.band = NL80211_BAND_6GHZ,
+	.center_freq = 5975,
+};
+
+static struct ieee80211_channel chan_6ghz_105 = {
+	.band = NL80211_BAND_6GHZ,
+	.center_freq = 6475,
+};
+
+static const struct chandef_compat_case {
+	const char *desc;
+	/* leave c1 empty for tests for identical */
+	struct cfg80211_chan_def c1, c2;
+	/* we test both ways around, so c2 should always be the compat one */
+	bool compat;
+} chandef_compat_cases[] = {
+	{
+		.desc = "identical non-HT",
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_20_NOHT,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "identical 20 MHz",
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_20,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "identical 40 MHz",
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_40,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955 + 10,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "identical 80 MHz",
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_80,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955 + 10 + 20,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "identical 160 MHz",
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955 + 10 + 20 + 40,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "identical 320 MHz",
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955 + 10 + 20 + 40 + 80,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "20 MHz in 320 MHz\n",
+		.c1 = {
+			.width = NL80211_CHAN_WIDTH_20,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955,
+		},
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955 + 10 + 20 + 40 + 80,
+		},
+		.compat = true,
+	},
+	{
+		.desc = "different 20 MHz",
+		.c1 = {
+			.width = NL80211_CHAN_WIDTH_20,
+			.chan = &chan_6ghz_1,
+			.center_freq1 = 5955,
+		},
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_20,
+			.chan = &chan_6ghz_5,
+			.center_freq1 = 5975,
+		},
+	},
+	{
+		.desc = "different primary 160 MHz",
+		.c1 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 150,
+		},
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 - 10,
+		},
+	},
+	{
+		/* similar to previous test but one has lower BW */
+		.desc = "matching primary 160 MHz",
+		.c1 = {
+			.width = NL80211_CHAN_WIDTH_160,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 + 70,
+		},
+		.c2 = {
+			.width = NL80211_CHAN_WIDTH_320,
+			.chan = &chan_6ghz_105,
+			.center_freq1 = 6475 - 10,
+		},
+		.compat = true,
+	},
+};
+
+KUNIT_ARRAY_PARAM_DESC(chandef_compat, chandef_compat_cases, desc)
+
+static void test_chandef_compat(struct kunit *test)
+{
+	const struct chandef_compat_case *params = test->param_value;
+	const struct cfg80211_chan_def *ret, *expect;
+	struct cfg80211_chan_def c1 = params->c1;
+
+	/* tests with identical ones */
+	if (!params->c1.chan)
+		c1 = params->c2;
+
+	KUNIT_EXPECT_EQ(test, cfg80211_chandef_valid(&c1), true);
+	KUNIT_EXPECT_EQ(test, cfg80211_chandef_valid(&params->c2), true);
+
+	expect = params->compat ? &params->c2 : NULL;
+
+	ret = cfg80211_chandef_compatible(&c1, &params->c2);
+	KUNIT_EXPECT_PTR_EQ(test, ret, expect);
+
+	if (!params->c1.chan)
+		expect = &c1;
+
+	ret = cfg80211_chandef_compatible(&params->c2, &c1);
+	KUNIT_EXPECT_PTR_EQ(test, ret, expect);
+}
+
+static struct kunit_case chandef_compat_test_cases[] = {
+	KUNIT_CASE_PARAM(test_chandef_compat, chandef_compat_gen_params),
+	{}
+};
+
+static struct kunit_suite chandef_compat = {
+	.name = "cfg80211-chandef-compat",
+	.test_cases = chandef_compat_test_cases,
+};
+
+kunit_test_suite(chandef_compat);