zephyr: tests: Test common/flash.c crec_flash_is_erased()

Test the crec_flash_is_erased() function. Add a union of zero-length
arrays to `struct ec_params_flash_write` for convenience

BRANCH=None
BUG=b:236074365
TEST=./twister

Signed-off-by: Tristan Honscheid <honscheid@google.com>
Change-Id: Ica8fd3ce19fca3c87c0c0a2be8732dda6691cce4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3865658
Reviewed-by: Simon Glass <sjg@chromium.org>

2 files changed, 68 insertions, 1 deletions

diff --git a/include/ec_commands.h b/include/ec_commands.h
index 4f30a0f308..f971387e00 100644
--- a/include/ec_commands.h
+++ b/include/ec_commands.h
@@ -1744,7 +1744,14 @@ struct ec_params_flash_read {
 struct ec_params_flash_write {
 	uint32_t offset;
 	uint32_t size;
-	/* Followed by data to write */
+	/* Followed by data to write. This union allows accessing an
+	 * underlying buffer as uint32s or uint8s for convenience. This does not
+	 * increase the size of the struct.
+	 */
+	union {
+		uint32_t words32[0];
+		uint8_t bytes[0];
+	} data;
 } __ec_align4;
 
 /* Erase flash */
diff --git a/zephyr/test/drivers/default/src/flash.c b/zephyr/test/drivers/default/src/flash.c
index 17c4f65172..53c6fd1806 100644
--- a/zephyr/test/drivers/default/src/flash.c
+++ b/zephyr/test/drivers/default/src/flash.c
@@ -356,6 +356,66 @@ ZTEST_USER(flash, test_console_cmd_flashwp__bad_param)
 	zassert_ok(!shell_execute_cmd(get_ec_shell(), "flashwp xyz"), NULL);
 }
 
+/**
+ * @brief Prepare a region of flash for the test_crec_flash_is_erased* tests
+ *
+ * @param offset Offset to write bytes at.
+ * @param size Number of bytes to erase.
+ * @param make_write If true, write an arbitrary byte after erase so the region
+ *                   is no longer fully erased.
+ */
+static void setup_flash_region_helper(uint32_t offset, uint32_t size,
+				      bool make_write)
+{
+	struct ec_params_flash_erase erase_params = {
+		.offset = offset,
+		.size = size,
+	};
+	struct host_cmd_handler_args erase_args =
+		BUILD_HOST_COMMAND_PARAMS(EC_CMD_FLASH_ERASE, 0, erase_params);
+
+	zassume_ok(host_command_process(&erase_args), NULL);
+
+	if (make_write) {
+		/* Sized for flash_write header plus one byte of data */
+		uint8_t out_buf[sizeof(struct ec_params_flash_write) +
+				sizeof(uint8_t)];
+
+		struct ec_params_flash_write *write_params =
+			(struct ec_params_flash_write *)out_buf;
+		struct host_cmd_handler_args write_args =
+			BUILD_HOST_COMMAND_SIMPLE(EC_CMD_FLASH_WRITE, 0);
+
+		write_params->offset = offset;
+		write_params->size = 1;
+		write_args.params = write_params;
+		write_args.params_size = sizeof(out_buf);
+
+		/* Write one byte at start of region */
+		out_buf[sizeof(*write_params)] = 0xec;
+
+		zassume_ok(host_command_process(&write_args), NULL);
+	}
+}
+
+ZTEST_USER(flash, test_crec_flash_is_erased__happy)
+{
+	uint32_t offset = 0x10000;
+
+	setup_flash_region_helper(offset, TEST_BUF_SIZE, false);
+
+	zassert_true(crec_flash_is_erased(offset, TEST_BUF_SIZE), NULL);
+}
+
+ZTEST_USER(flash, test_crec_flash_is_erased__not_erased)
+{
+	uint32_t offset = 0x10000;
+
+	setup_flash_region_helper(offset, TEST_BUF_SIZE, true);
+
+	zassert_true(!crec_flash_is_erased(offset, TEST_BUF_SIZE), NULL);
+}
+
 static void flash_reset(void)
 {
 	/* Set the GPIO WP_L to default */