[OSS-Tools] [PATCH platsch 3/5] allow directory/basename selection via environment

["Ulrich Ölmann" <u.oelmann@pengutronix.de>]

Introduce the possibility to choose the directory searched for the splash-
images, as well as the images' basename via the process' environment

  platsch_directory=/usr/share/plitschplatsch
  platsch_basename=splosh

with the corresponding commandline parameters still having higher priority
compared to the environment.

The Kernel passes unrecognized key-value parameters not containing dots into
init’s environment [1]. So the above environment variable can be supplied via
the kernel commandline. This also allows dynamic use cases where the bootloader
decides which resolution to use on which connector.

[1] https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html

Signed-off-by: Ulrich Ölmann <u.oelmann@pengutronix.de>
---
 README.rst | 12 ++++++++----
 platsch.c  |  9 +++++++++
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/README.rst b/README.rst
index 07f60177b510..96337bfd49f2 100644
--- a/README.rst
+++ b/README.rst
@@ -74,6 +74,12 @@ file::
 Configuration
 -------------
 
+The directory searched for the splash images (default: ``/usr/share/platsch``),
+as well as the image files' basename (default: ``splash``) can be controlled via
+the environment variables ``platsch_directory`` and ``platsch_basename`` (which
+in the case of PID != 1 would be overridden by the corresponding commandline
+parameters, see further downwards).
+
 For each connector a corresponding environment variable is looked up::
 
   platsch_<connector-type-name><connector-type-id>_mode
@@ -105,11 +111,9 @@ Debugging
 
 For debugging purposes, platsch recognizes a couple of command line arguments:
 
-``--directory`` or ``-d`` sets the directory containing the splash screens
-(default: ``/usr/share/platsch``).
+``--directory`` or ``-d`` sets the directory containing the splash screens.
 
-``--basename`` or ``-b`` sets the prefix of the splash screen file names
-(default: ``splash``).
+``--basename`` or ``-b`` sets the prefix of the splash screen file names.
 
 Contributing
 ------------
diff --git a/platsch.c b/platsch.c
index 8228b2f8a886..535b589a659a 100644
--- a/platsch.c
+++ b/platsch.c
@@ -567,8 +567,17 @@ int main(int argc, char *argv[])
 	bool pid1 = getpid() == 1;
 	const char *dir = "/usr/share/platsch";
 	const char *base = "splash";
+	const char *env;
 	int ret = 0, c, i;
 
+	env = getenv("platsch_directory");
+	if (env)
+		dir = env;
+
+	env = getenv("platsch_basename");
+	if (env)
+		base = env;
+
 	if (!pid1) {
 		while ((c = getopt_long(argc, argv, "hd:b:", longopts, NULL)) != EOF) {
 			switch(c) {
-- 
2.39.2