[PATCH RFC 26/26] dma-buf: Add kunit tests for mapping type

Jason Gunthorpe
2026-02-18T00:12:20Z

Some basic coverage of common flows:
- Check dma_buf_match_mapping()'s rules. These choices effectively
become driver facing API and it would be a pain to change them later
- Test the dma_bug_sgt attachment flow to see that the new wrappers work

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
drivers/dma-buf/Makefile | 1 +
drivers/dma-buf/st-dma-mapping.c | 373 +++++++++++++++++++++++++++++++
2 files changed, 374 insertions(+)
create mode 100644 drivers/dma-buf/st-dma-mapping.c

diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile
index 12c86da25866c1..0ba311be8d3547 100644
--- a/drivers/dma-buf/Makefile
+++ b/drivers/dma-buf/Makefile
@@ -12,6 +12,7 @@ dmabuf_kunit-y := \
st-dma-fence.o \
st-dma-fence-chain.o \
st-dma-fence-unwrap.o \
+ st-dma-mapping.o \
st-dma-resv.o

obj-$(CONFIG_DMABUF_KUNIT_TEST) += dmabuf_kunit.o
diff --git a/drivers/dma-buf/st-dma-mapping.c b/drivers/dma-buf/st-dma-mapping.c
new file mode 100644
index 00000000000000..1bccfe43a576d0
--- /dev/null
+++ b/drivers/dma-buf/st-dma-mapping.c
@@ -0,0 +1,373 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit tests for dma_buf_match_mapping()
+ */
+
+#include <kunit/device.h>
+#include <kunit/test.h>
+#include <linux/dma-buf.h>
+#include <linux/dma-buf-mapping.h>
+#include <linux/errno.h>
+
+/* Mock tracking state -- reset before each test */
+static bool mock_match_called;
+static const struct dma_buf_mapping_match *mock_match_exp_arg;
+static const struct dma_buf_mapping_match *mock_match_imp_arg;
+static int mock_match_ret;
+
+static bool mock_finish_called;
+static const struct dma_buf_match_args *mock_finish_args_arg;
+static const struct dma_buf_mapping_match *mock_finish_exp_arg;
+static const struct dma_buf_mapping_match *mock_finish_imp_arg;
+
+static int reset_mock_state(struct kunit *test)
+{
+ mock_match_called = false;
+ mock_match_exp_arg = NULL;
+ mock_match_imp_arg = NULL;
+ mock_match_ret = 0;
+ mock_finish_called = false;
+ mock_finish_args_arg = NULL;
+ mock_finish_exp_arg = NULL;
+ mock_finish_imp_arg = NULL;
+ return 0;
+}
+
+static int mock_match(struct dma_buf *dmabuf,
+ const struct dma_buf_mapping_match *exp,
+ const struct dma_buf_mapping_match *imp)
+{
+ mock_match_called = true;
+ mock_match_exp_arg = exp;
+ mock_match_imp_arg = imp;
+ return mock_match_ret;
+}
+
+static void mock_finish_match(struct dma_buf_match_args *args,
+ const struct dma_buf_mapping_match *exp,
+ const struct dma_buf_mapping_match *imp)
+{
+ mock_finish_called = true;
+ mock_finish_args_arg = args;
+ mock_finish_exp_arg = exp;
+ mock_finish_imp_arg = imp;
+
+ /* Test doesn't always set attach */
+ if (args->attach)
+ args->attach->map_type = (struct dma_buf_mapping_match){
+ .type = exp->type,
+ .exp_ops = exp->exp_ops,
+ };
+}
+
+/* Type with both match and finish_match callbacks */
+static struct dma_buf_mapping_type mock_type_a = {
+ .name = "mock_type_a",
+ .match = mock_match,
+ .finish_match = mock_finish_match,
+};
+
+/* Second type -- distinct pointer identity from A */
+static struct dma_buf_mapping_type mock_type_b = {
+ .name = "mock_type_b",
+ .match = mock_match,
+ .finish_match = mock_finish_match,
+};
+
+static void test_match_fail(struct kunit *test)
+{
+ struct dma_buf_mapping_match matches[] = { { .type = &mock_type_a } };
+ struct dma_buf_mapping_match exp[] = { { .type = &mock_type_b } };
+ struct dma_buf_match_args args = {
+ .imp_matches = matches,
+ .imp_len = ARRAY_SIZE(matches),
+ };
+
+ /* Zero-length exporter array returns -EINVAL */
+ KUNIT_EXPECT_EQ(test, dma_buf_match_mapping(&args, NULL, 0), -EINVAL);
+ KUNIT_EXPECT_FALSE(test, mock_match_called);
+ KUNIT_EXPECT_FALSE(test, mock_finish_called);
+
+ /* Zero-length importer array returns -EINVAL */
+ args = (struct dma_buf_match_args){};
+ KUNIT_EXPECT_EQ(test,
+ dma_buf_match_mapping(&args, matches,
+ ARRAY_SIZE(matches)),
+ -EINVAL);
+ KUNIT_EXPECT_FALSE(test, mock_match_called);
+ KUNIT_EXPECT_FALSE(test, mock_finish_called);
+
+ /* Different types produce no match */
+ KUNIT_EXPECT_EQ(test,
+ dma_buf_match_mapping(&args, exp, ARRAY_SIZE(exp)),
+ -EINVAL);
+ KUNIT_EXPECT_FALSE(test, mock_match_called);
+ KUNIT_EXPECT_FALSE(test, mock_finish_called);
+}
+
+/* When type->match() is NULL same types always match */
+static void test_match_no_match_callback(struct kunit *test)
+{
+ static struct dma_buf_mapping_type mock_type_no_match = {
+ .name = "mock_type_no_match",
+ .finish_match = mock_finish_match,
+ };
+ struct dma_buf_mapping_match matches[] = {
+ { .type = &mock_type_no_match }
+ };
+ struct dma_buf_match_args args = {
+ .imp_matches = matches,
+ .imp_len = ARRAY_SIZE(matches),
+ };
+
+ KUNIT_EXPECT_EQ(
+ test,
+ dma_buf_match_mapping(&args, matches, ARRAY_SIZE(matches)), 0);
+ KUNIT_EXPECT_FALSE(test, mock_match_called);
+ KUNIT_EXPECT_TRUE(test, mock_finish_called);
+ KUNIT_EXPECT_PTR_EQ(test, mock_finish_args_arg, &args);
+ KUNIT_EXPECT_PTR_EQ(test, mock_finish_exp_arg, &matches[0]);
+ KUNIT_EXPECT_PTR_EQ(test, mock_finish_imp_arg, &matches[0]);
+}
+
+static void test_match_callback_returns(struct kunit *test)
+{
+ struct dma_buf_mapping_match matches[] = { { .type = &mock_type_a } };
+ struct dma_buf_match_args args = {
+ .imp_matches = matches,
+ .imp_len = ARRAY_SIZE(matches),
+ };
+
+ /* type->match() returns -EOPNOTSUPP. Skips to next */
+ mock_match_ret = -EOPNOTSUPP;
+ KUNIT_EXPECT_EQ(test,
+ dma_buf_match_mapping(&args, matches,
+ ARRAY_SIZE(matches)),
+ -EINVAL);
+ KUNIT_EXPECT_TRUE(test, mock_match_called);
+ KUNIT_EXPECT_FALSE(test, mock_finish_called);
+
+ /* type->match() returns an error code. Stops immediately, returns code */
+ mock_match_ret = -ENOMEM;
+ KUNIT_EXPECT_EQ(test,
+ dma_buf_match_mapping(&args, matches,
+ ARRAY_SIZE(matches)),
+ -ENOMEM);
+ KUNIT_EXPECT_TRUE(test, mock_match_called);
+ KUNIT_EXPECT_FALSE(test, mock_finish_called);
+}
+
+/* Multiple importers. First exporter compatible type wins */
+static void test_match_exporter_priority(struct kunit *test)
+{
+ struct dma_buf_mapping_match exp1[2] = {
+ { .type = &mock_type_a },
+ { .type = &mock_type_b },
+ };
+ struct dma_buf_mapping_match exp2[] = { { .type = &mock_type_b } };
+ struct dma_buf_mapping_match imp[2] = {
+ { .type = &mock_type_a },
+ { .type = &mock_type_b },
+ };
+ struct dma_buf_match_args args = {
+ .imp_matches = imp,
+ .imp_len = ARRAY_SIZE(imp),
+ };
+
+ /* First matches */
+ KUNIT_EXPECT_EQ(
+ test, dma_buf_match_mapping(&args, exp1, ARRAY_SIZE(exp1)), 0);
+ KUNIT_EXPECT_TRUE(test, mock_finish_called);
+ KUNIT_EXPECT_PTR_EQ(test, mock_finish_exp_arg, &exp1[0]);
+ KUNIT_EXPECT_PTR_EQ(test, mock_finish_imp_arg, &imp[0]);
+
+ /* Second matches */
+ KUNIT_EXPECT_EQ(
+ test, dma_buf_match_mapping(&args, exp2, ARRAY_SIZE(exp2)), 0);
+ KUNIT_EXPECT_TRUE(test, mock_finish_called);
+ KUNIT_EXPECT_PTR_EQ(test, mock_finish_exp_arg, &exp2[0]);
+ KUNIT_EXPECT_PTR_EQ(test, mock_finish_imp_arg, &imp[1]);
+}
+
+/* Multiple exporters. First exporter compatible type wins */
+static void test_match_importer_priority(struct kunit *test)
+{
+ struct dma_buf_mapping_match exp[] = {
+ { .type = &mock_type_a },
+ { .type = &mock_type_b },
+ };
+ struct dma_buf_mapping_match imp1[] = { { .type = &mock_type_b } };
+ struct dma_buf_mapping_match imp2[] = {
+ { .type = &mock_type_b },
+ { .type = &mock_type_a },
+ };
+ struct dma_buf_match_args args = {
+ .imp_matches = imp1,
+ .imp_len = ARRAY_SIZE(imp1),
+ };
+
+ /* Single importer */
+ KUNIT_EXPECT_EQ(test,
+ dma_buf_match_mapping(&args, exp, ARRAY_SIZE(exp)), 0);
+ KUNIT_EXPECT_TRUE(test, mock_finish_called);
+ KUNIT_EXPECT_PTR_EQ(test, mock_finish_exp_arg, &exp[1]);
+ KUNIT_EXPECT_PTR_EQ(test, mock_finish_imp_arg, &imp1[0]);
+
+ /* Two importers, skipping the first */
+ args = (struct dma_buf_match_args){
+ .imp_matches = imp2,
+ .imp_len = ARRAY_SIZE(imp2),
+ };
+ KUNIT_EXPECT_EQ(test,
+ dma_buf_match_mapping(&args, exp, ARRAY_SIZE(exp)), 0);
+ KUNIT_EXPECT_TRUE(test, mock_finish_called);
+ KUNIT_EXPECT_PTR_EQ(test, mock_finish_exp_arg, &exp[0]);
+ KUNIT_EXPECT_PTR_EQ(test, mock_finish_imp_arg, &imp2[1]);
+}
+
+static void mock_dmabuf_release(struct dma_buf *dmabuf)
+{
+}
+
+static struct sg_table *mock_map_dma_buf(struct dma_buf_attachment *attach,
+ enum dma_data_direction dir)
+{
+ return ERR_PTR(-ENODEV);
+}
+
+static void mock_unmap_dma_buf(struct dma_buf_attachment *attach,
+ struct sg_table *sgt,
+ enum dma_data_direction dir)
+{
+}
+
+static const struct dma_buf_mapping_sgt_exp_ops mock_sgt_ops = {
+ .map_dma_buf = mock_map_dma_buf,
+ .unmap_dma_buf = mock_unmap_dma_buf,
+};
+
+static const struct dma_buf_ops mock_dmabuf_simple_sgt_ops = {
+ .release = mock_dmabuf_release,
+ DMA_BUF_SIMPLE_SGT_EXP_MATCH(mock_map_dma_buf, mock_unmap_dma_buf),
+};
+
+static int mock_dmabuf_match_mapping(struct dma_buf_match_args *args)
+{
+ struct dma_buf_mapping_match sgt_match[2];
+ unsigned int num_match = 0;
+
+ sgt_match[num_match++] =
+ (struct dma_buf_mapping_match){ .type = &mock_type_a };
+
+ sgt_match[num_match++] = DMA_BUF_EMAPPING_SGT(&mock_sgt_ops);
+
+ return dma_buf_match_mapping(args, sgt_match, ARRAY_SIZE(sgt_match));
+}
+
+static const struct dma_buf_ops mock_dmabuf_two_exp_ops = {
+ .release = mock_dmabuf_release,
+ .match_mapping = mock_dmabuf_match_mapping,
+};
+
+struct dma_exporter {
+ const struct dma_buf_ops *ops;
+ const char *desc;
+};
+
+static struct dma_buf *mock_dmabuf_export(const struct dma_buf_ops *ops)
+{
+ DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+ exp_info.ops = ops;
+ exp_info.size = PAGE_SIZE;
+ exp_info.priv = ERR_PTR(-EINVAL);
+ return dma_buf_export(&exp_info);
+}
+
+/*
+ * Check that a simple SGT exporter with single_exporter_match works with
+ * dma_buf_sgt_attach()
+ */
+static void test_sgt_attach(struct kunit *test)
+{
+ const struct dma_exporter *param = test->param_value;
+ struct dma_buf *dmabuf;
+ struct dma_buf_attachment *attach;
+ struct device *dev;
+
+ dev = kunit_device_register(test, "dma-buf-test");
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+
+ dmabuf = mock_dmabuf_export(param->ops);
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dmabuf);
+
+ attach = dma_buf_sgt_attach(dmabuf, dev);
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, attach);
+
+ KUNIT_EXPECT_PTR_EQ(test, attach->map_type.type,
+ &dma_buf_mapping_sgt_type);
+ KUNIT_EXPECT_PTR_EQ(test, dma_buf_sgt_dma_device(attach), dev);
+ KUNIT_EXPECT_FALSE(test, dma_buf_sgt_p2p_allowed(attach));
+
+ dma_buf_detach(dmabuf, attach);
+ dma_buf_put(dmabuf);
+}
+
+static void mock_move_notify(struct dma_buf_attachment *attach)
+{
+}
+
+static const struct dma_buf_attach_ops mock_importer_ops = {
+ .move_notify = &mock_move_notify,
+};
+
+/* Check a dynamic attach with a non-sgt mapping type */
+static void test_mock_attach(struct kunit *test)
+{
+ struct dma_buf_mapping_match imp[] = { { .type = &mock_type_a } };
+ struct dma_buf *dmabuf;
+ struct dma_buf_attachment *attach;
+ struct device *dev;
+
+ dev = kunit_device_register(test, "dma-buf-test");
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+
+ dmabuf = mock_dmabuf_export(&mock_dmabuf_two_exp_ops);
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dmabuf);
+
+ attach = dma_buf_mapping_attach(dmabuf, imp, ARRAY_SIZE(imp),
+ &mock_importer_ops, NULL);
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, attach);
+
+ KUNIT_EXPECT_PTR_EQ(test, attach->map_type.type, &mock_type_a);
+
+ dma_buf_detach(dmabuf, attach);
+ dma_buf_put(dmabuf);
+}
+
+static const struct dma_exporter dma_exporter_params[] = {
+ { &mock_dmabuf_simple_sgt_ops, "simple_sgt" },
+ { &mock_dmabuf_two_exp_ops, "two_exp" },
+};
+KUNIT_ARRAY_PARAM_DESC(dma_exporter, dma_exporter_params, desc);
+
+static struct kunit_case dma_mapping_cases[] = {
+ KUNIT_CASE(test_match_fail),
+ KUNIT_CASE(test_match_no_match_callback),
+ KUNIT_CASE(test_match_callback_returns),
+ KUNIT_CASE(test_match_exporter_priority),
+ KUNIT_CASE(test_match_importer_priority),
+ KUNIT_CASE_PARAM(test_sgt_attach, dma_exporter_gen_params),
+ KUNIT_CASE(test_mock_attach),
+ {}
+};
+
+static struct kunit_suite dma_mapping_test_suite = {
+ .name = "dma-buf-mapping",
+ .init = reset_mock_state,
+ .test_cases = dma_mapping_cases,
+};
+
+kunit_test_suite(dma_mapping_test_suite);
+
+MODULE_IMPORT_NS("DMA_BUF");
--
2.43.0