[PATCH RFT 2/9] globalvar: skip empty variables in globalvar_get_match()

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

globalvar_get_match() concatenates all matching variables with the
separator, whether they have a value or not. As variables like
global.linux.bootargs.base or global.linux.bootargs.dyn.* are registered
unconditionally, but often left empty, the resulting kernel command line
would contain runs of multiple spaces.

Treat variables without a value as if they didn't exist at all.

Assisted-by: Claude:fable-5
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 Documentation/user/booting-linux.rst | 2 +-
 common/globalvar.c                   | 6 +++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Documentation/user/booting-linux.rst b/Documentation/user/booting-linux.rst
index 95834786b67a..fa5a355183eb 100644
--- a/Documentation/user/booting-linux.rst
+++ b/Documentation/user/booting-linux.rst
@@ -87,7 +87,7 @@ With ``CONFIG_FLEXIBLE_BOOTARGS`` enabled, the bootargs are composed
 from different :ref:`global device<global_device>` variables and the
 :ref:`bootargs <magicvar_bootargs>` environment variable is ignored.
 All variables beginning with ``global.linux.bootargs.`` will be concatenated
-to the bootargs:
+to the bootargs. Variables without a value are skipped:
 
 .. code-block:: sh
 
diff --git a/common/globalvar.c b/common/globalvar.c
index 876379b2538e..41f3e93b00e1 100644
--- a/common/globalvar.c
+++ b/common/globalvar.c
@@ -7,6 +7,7 @@
 #include <init.h>
 #include <environment.h>
 #include <magicvar.h>
+#include <string.h>
 #include <fs.h>
 #include <fcntl.h>
 #include <libfile.h>
@@ -419,7 +420,8 @@ void globalvar_print(void)
  * globalvar_get_match
  *
  * get a concatenated string of all globalvars beginning with 'match'.
- * This adds whitespaces between the different globalvars
+ * This adds the separator between the different globalvars. Variables
+ * without a value are skipped.
  */
 char *globalvar_get_match(const char *match, const char *separator)
 {
@@ -429,6 +431,8 @@ char *globalvar_get_match(const char *match, const char *separator)
 	dev_for_each_param(&global_device, param) {
 		if (!strncmp(match, param->name, strlen(match))) {
 			const char *p = dev_get_param(&global_device, param->name);
+			if (isempty(p))
+				continue;
 			if (val) {
 				char *new = basprintf("%s%s%s", val,
 							separator, p);
-- 
2.47.3