sar: Fix semantics of `get_wifi_sar_cbfs_filename()`

Currently, if `get_wifi_sar_cbfs_filename()` returns NULL, then
`get_wifi_sar_limits()` assumes that the default filename is used for
CBFS SAR file. This prevents a board from supporting different models
using the same firmware -- some which require SAR support and some
which don't.

This change updates the logic in `get_wifi_sar_limits()` to return
early if filename is not provided by the mainboard. In order to
maintain the same logic as before, current mainboards are updated to
return WIFI_SAR_CBFS_DEFAULT_FILENAME instead of NULL in default
case.

Change-Id: I68b5bdd213767a3cd81fe41ace66540acd68e26a
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51485
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 2 insertions, 4 deletions

diff --git a/src/mainboard/google/hatch/variants/dratini/variant.c b/src/mainboard/google/hatch/variants/dratini/variant.c
index 1a4cd4049b..72f62316e3 100644
--- a/src/mainboard/google/hatch/variants/dratini/variant.c
+++ b/src/mainboard/google/hatch/variants/dratini/variant.c
@@ -7,7 +7,6 @@
 
 const char *get_wifi_sar_cbfs_filename(void)
 {
-	const char *filename = NULL;
 	uint32_t sku_id = google_chromeec_get_board_sku();
 
 	switch (sku_id) {
@@ -15,8 +14,7 @@ const char *get_wifi_sar_cbfs_filename(void)
 	case SKU_22_DRAGONAIR:
 	case SKU_23_DRAGONAIR:
 	case SKU_24_DRAGONAIR:
-		filename = "wifi_sar-dragonair.hex";
-		break;
+		return "wifi_sar-dragonair.hex";
 	}
-	return filename;
+	return WIFI_SAR_CBFS_DEFAULT_FILENAME;
 }