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>

4 files changed, 8 insertions, 16 deletions

diff --git a/src/mainboard/google/dedede/variants/drawcia/variant.c b/src/mainboard/google/dedede/variants/drawcia/variant.c
index 0c2290432e..9dc0028e7c 100644
--- a/src/mainboard/google/dedede/variants/drawcia/variant.c
+++ b/src/mainboard/google/dedede/variants/drawcia/variant.c
@@ -6,12 +6,10 @@
 
 const char *get_wifi_sar_cbfs_filename(void)
 {
-	const char *filename = NULL;
-
 	if (fw_config_probe(FW_CONFIG(TABLETMODE, TABLETMODE_ENABLED)))
-		filename = "wifi_sar-drawcia.hex";
+		return "wifi_sar-drawcia.hex";
 
-	return filename;
+	return WIFI_SAR_CBFS_DEFAULT_FILENAME;
 }
 
 const char *mainboard_vbt_filename(void)
diff --git a/src/mainboard/google/dedede/variants/galtic/variant.c b/src/mainboard/google/dedede/variants/galtic/variant.c
index e7b1bb8ccd..92aa1767cf 100644
--- a/src/mainboard/google/dedede/variants/galtic/variant.c
+++ b/src/mainboard/google/dedede/variants/galtic/variant.c
@@ -5,9 +5,7 @@
 
 const char *get_wifi_sar_cbfs_filename(void)
 {
-	const char *filename = NULL;
-
 	if (fw_config_probe(FW_CONFIG(TABLETMODE, TABLETMODE_ENABLED)))
-		filename = "wifi_sar-galtic.hex";
-	return filename;
+		return "wifi_sar-galtic.hex";
+	return WIFI_SAR_CBFS_DEFAULT_FILENAME;
 }
diff --git a/src/mainboard/google/dedede/variants/madoo/variant.c b/src/mainboard/google/dedede/variants/madoo/variant.c
index b8c3654ab0..94e4d9023c 100644
--- a/src/mainboard/google/dedede/variants/madoo/variant.c
+++ b/src/mainboard/google/dedede/variants/madoo/variant.c
@@ -5,10 +5,8 @@
 
 const char *get_wifi_sar_cbfs_filename(void)
 {
-	const char *filename = NULL;
-
 	if (fw_config_probe(FW_CONFIG(TABLETMODE, TABLETMODE_ENABLED)))
-		filename = "wifi_sar-madoo.hex";
+		return "wifi_sar-madoo.hex";
 
-	return filename;
+	return WIFI_SAR_CBFS_DEFAULT_FILENAME;
 }
diff --git a/src/mainboard/google/dedede/variants/magolor/variant.c b/src/mainboard/google/dedede/variants/magolor/variant.c
index e3b9599a91..68ce6c2316 100644
--- a/src/mainboard/google/dedede/variants/magolor/variant.c
+++ b/src/mainboard/google/dedede/variants/magolor/variant.c
@@ -5,10 +5,8 @@
 
 const char *get_wifi_sar_cbfs_filename(void)
 {
-	const char *filename = NULL;
-
 	if (fw_config_probe(FW_CONFIG(TABLETMODE, TABLETMODE_ENABLED)))
-		filename = "wifi_sar-magolor.hex";
+		return "wifi_sar-magolor.hex";
 
-	return filename;
+	return WIFI_SAR_CBFS_DEFAULT_FILENAME;
 }