[PATCH v3] lib/igt_rc: Introduce generic config parser

[Mark Yacoub <markyacoub@google.com>]

Currently, libraries like unigraf explicitly rely on GKeyFile
for reading configuration from .igtrc. Android builds do not
natively supply glib, meaning these tools cannot be cleanly
compiled.

This patch abstracts config parsing into a dedicated `igt_rc` module.
To avoid platform-specific diverging implementations and glib dependencies,
`igt_rc` now natively parses `.igtrc` using a stripped-down, thread-safe
`igt_list` implementation for all platforms.

v3:
 - Drop Android-specific fallback paths; use IGT_CONFIG_PATH natively.
 - Drop glib Linux wrappers entirely; unify a single generic parser for all platforms.
 - Port manual linked-list tracking over to standard igt_list.h APIs.
 - Inherit base 0 for strtol to safely parse hex masks.
 - Use robust PATH_MAX for dynamic config paths.
 - Update pointer assignments, array indexing [0], and public docstrings (Louis Chauvet).

v2:
 - Drop the GKeyFile abstraction fakes from android/glib.h.
 - Introduce a generic wrapper (igt_rc.h) instead of modifying glib.h.
---
 lib/igt_rc.c                 | 201 +++++++++++++++++++++++++++++++++++
 lib/igt_rc.h                 |   5 +
 lib/meson.build              |   1 +
 lib/vendor/unigraf/unigraf.c |  92 +++++++---------
 4 files changed, 247 insertions(+), 52 deletions(-)
 create mode 100644 lib/igt_rc.c

diff --git a/lib/igt_rc.c b/lib/igt_rc.c
new file mode 100644
index 000000000..17a852393
--- /dev/null
+++ b/lib/igt_rc.c
@@ -0,0 +1,201 @@
+#include "igt_rc.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <ctype.h>
+#include <pthread.h>
+#include <limits.h>
+#include "igt_list.h"
+
+struct igt_key_entry {
+	char *group;
+	char *key;
+	char *value;
+	struct igt_list_head link;
+};
+
+static IGT_LIST_HEAD(rc_entries);
+static pthread_once_t rc_once_control = PTHREAD_ONCE_INIT;
+
+static char *trim_whitespace(char *str)
+{
+	char *end;
+
+	while (isspace((unsigned char)str[0]))
+		str++;
+
+	if (str[0] == 0)
+		return str;
+
+	end = str + strlen(str) - 1;
+	while (end > str && isspace((unsigned char)end[0]))
+		end--;
+
+	end[1] = '\0';
+	return str;
+}
+
+static void load_igtrc_once(void)
+{
+	FILE *fp;
+	char *line = NULL;
+	size_t len = 0;
+	ssize_t read;
+	char *current_group = NULL;
+	char path[PATH_MAX];
+
+	char *config_path = getenv("IGT_CONFIG_PATH");
+	if (config_path) {
+		snprintf(path, sizeof(path), "%s", config_path);
+	} else {
+		char *home = getenv("HOME");
+		if (!home)
+			home = "";
+		snprintf(path, sizeof(path), "%s/.igtrc", home);
+	}
+
+	fp = fopen(path, "r");
+	if (!fp)
+		return;
+
+	while ((read = getline(&line, &len, fp)) != -1) {
+		char *trimmed = trim_whitespace(line);
+
+		if (trimmed[0] == '\0' || trimmed[0] == '#' || trimmed[0] == ';')
+			continue;
+
+		if (trimmed[0] == '[' && trimmed[strlen(trimmed) - 1] == ']') {
+			free(current_group);
+			trimmed[strlen(trimmed) - 1] = '\0';
+			current_group = strdup(trimmed + 1);
+			continue;
+		}
+
+		if (current_group) {
+			char *eq = strchr(trimmed, '=');
+
+			if (eq) {
+				char *key;
+				char *value;
+				struct igt_key_entry *entry;
+
+				eq[0] = '\0';
+				value = eq + 1;
+				key = trim_whitespace(trimmed);
+				value = trim_whitespace(value);
+
+				entry = calloc(1, sizeof(*entry));
+				entry->group = strdup(current_group);
+				entry->key = strdup(key);
+				entry->value = strdup(value);
+				igt_list_add_tail(&entry->link, &rc_entries);
+			}
+		}
+	}
+
+	free(current_group);
+	free(line);
+	fclose(fp);
+}
+
+__attribute__((destructor))
+static void free_igtrc(void)
+{
+	struct igt_key_entry *curr, *tmp;
+
+	igt_list_for_each_entry_safe(curr, tmp, &rc_entries, link) {
+		free(curr->group);
+		free(curr->key);
+		free(curr->value);
+		free(curr);
+	}
+	IGT_INIT_LIST_HEAD(&rc_entries);
+}
+
+/**
+ * igt_rc_get_string:
+ * @group_name: The group name in the config file.
+ * @key: The key to look up.
+ *
+ * Looks up a string configuration value in the `.igtrc` file.
+ * The returned string is newly allocated and must be freed by 
+ * the caller using free().
+ *
+ * Returns: A newly allocated string containing the value, or NULL if not found.
+ */
+char *igt_rc_get_string(const char *group_name, const char *key)
+{
+	char *last_match = NULL;
+	struct igt_key_entry *curr;
+
+	pthread_once(&rc_once_control, load_igtrc_once);
+
+	igt_list_for_each_entry(curr, &rc_entries, link) {
+		if (strcmp(curr->group, group_name) == 0 && strcmp(curr->key, key) == 0)
+			last_match = curr->value;
+	}
+
+	return last_match ? strdup(last_match) : NULL;
+}
+
+/**
+ * igt_rc_get_boolean:
+ * @group_name: The group name in the config file.
+ * @key: The key to look up.
+ * @out: Pointer to a boolean where the result will be stored.
+ *
+ * Looks up a boolean configuration value in the `.igtrc` file.
+ * Parses standard boolean representations like "true", "false", "1", "0".
+ *
+ * Returns: true if the key exists and was successfully parsed, false otherwise.
+ */
+bool igt_rc_get_boolean(const char *group_name, const char *key, bool *out)
+{
+	char *val = igt_rc_get_string(group_name, key);
+
+	if (!val)
+		return false;
+
+	if (strcasecmp(val, "true") == 0 || strcmp(val, "1") == 0) {
+		*out = true;
+	} else if (strcasecmp(val, "false") == 0 || strcmp(val, "0") == 0) {
+		*out = false;
+	} else {
+		free(val);
+		return false;
+	}
+
+	free(val);
+	return true;
+}
+
+/**
+ * igt_rc_get_integer:
+ * @group_name: The group name in the config file.
+ * @key: The key to look up.
+ * @out: Pointer to an integer where the result will be stored.
+ *
+ * Looks up an integer configuration value in the `.igtrc` file.
+ *
+ * Returns: true if the key exists and was successfully parsed, false otherwise.
+ */
+bool igt_rc_get_integer(const char *group_name, const char *key, int *out)
+{
+	char *val = igt_rc_get_string(group_name, key);
+	char *endptr;
+	long lval;
+
+	if (!val)
+		return false;
+
+	lval = strtol(val, &endptr, 0);
+	if (endptr[0] != '\0') {
+		free(val);
+		return false;
+	}
+
+	*out = (int)lval;
+	free(val);
+	return true;
+}
diff --git a/lib/igt_rc.h b/lib/igt_rc.h
index d871b3b26..8746ff70b 100644
--- a/lib/igt_rc.h
+++ b/lib/igt_rc.h
@@ -1,3 +1,4 @@
+#include <stdbool.h>
 /*
  * Copyright © 2017 Intel Corporation
  *
@@ -33,4 +34,8 @@
 
 extern GKeyFile *igt_key_file;
 
+char *igt_rc_get_string(const char *group_name, const char *key);
+bool igt_rc_get_boolean(const char *group_name, const char *key, bool *out);
+bool igt_rc_get_integer(const char *group_name, const char *key, int *out);
+
 #endif /* IGT_RC_H */
diff --git a/lib/meson.build b/lib/meson.build
index 12d78de20..5348f2da0 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -97,6 +97,7 @@ lib_sources = [
 	'igt_kms.c',
 	'igt_fb.c',
 	'igt_core.c',
+	'igt_rc.c',
 	'igt_dir.c',
 	'igt_draw.c',
 	'igt_list.c',
diff --git a/lib/vendor/unigraf/unigraf.c b/lib/vendor/unigraf/unigraf.c
index 30ee3c72b..a6b3008eb 100644
--- a/lib/vendor/unigraf/unigraf.c
+++ b/lib/vendor/unigraf/unigraf.c
@@ -364,7 +364,6 @@ int unigraf_get_connector_id_by_stream(int drm_fd, int stream_id)
 bool unigraf_open_device(int drm_fd)
 {
 	TSI_RESULT r;
-	GError *cfg_error = NULL;
 	char *cfg_device = NULL;
 	char *cfg_role = NULL;
 	char *cfg_input = NULL;
@@ -382,63 +381,52 @@ bool unigraf_open_device(int drm_fd)
 
 	unigraf_init();
 
-	if (igt_key_file) {
-		cfg_device = g_key_file_get_string(igt_key_file, UNIGRAF_CONFIG_GROUP,
-						   UNIGRAF_CONFIG_DEVICE_NAME, &cfg_error);
-		if (cfg_error) {
-			unigraf_debug("No device name configured, uses first device available.\n");
-			cfg_device = NULL;
-		}
+	cfg_device = igt_rc_get_string(UNIGRAF_CONFIG_GROUP,
+				       UNIGRAF_CONFIG_DEVICE_NAME);
+	if (!cfg_device) {
+		unigraf_debug("No device name configured, uses first device available.\n");
+		cfg_device = NULL;
+	}
 
-		cfg_error = NULL;
-		cfg_role = g_key_file_get_string(igt_key_file, UNIGRAF_CONFIG_GROUP,
-						 UNIGRAF_CONFIG_DEVICE_ROLE, &cfg_error);
-		if (cfg_error) {
-			unigraf_debug("No device role configured.\n");
-			cfg_role = NULL;
-		}
+	cfg_role = igt_rc_get_string(UNIGRAF_CONFIG_GROUP,
+				     UNIGRAF_CONFIG_DEVICE_ROLE);
+	if (!cfg_role) {
+		unigraf_debug("No device role configured.\n");
+		cfg_role = NULL;
+	}
 
-		cfg_error = NULL;
-		cfg_input = g_key_file_get_string(igt_key_file, UNIGRAF_CONFIG_GROUP,
-						  UNIGRAF_CONFIG_INPUT_NAME, &cfg_error);
-		if (cfg_error) {
-			unigraf_debug("No input name configured.\n");
-			cfg_input = NULL;
-		}
+	cfg_input = igt_rc_get_string(UNIGRAF_CONFIG_GROUP,
+				      UNIGRAF_CONFIG_INPUT_NAME);
+	if (!cfg_input) {
+		unigraf_debug("No input name configured.\n");
+		cfg_input = NULL;
+	}
 
-		cfg_error = NULL;
-		unigraf_connector_name = g_key_file_get_string(igt_key_file, UNIGRAF_CONFIG_GROUP,
-							       UNIGRAF_CONFIG_CONNECTOR_NAME,
-							       &cfg_error);
-		if (cfg_error) {
-			unigraf_debug("No connector name configured, will autodetect.\n");
-			unigraf_connector_name = NULL;
-		}
+	unigraf_connector_name = igt_rc_get_string(UNIGRAF_CONFIG_GROUP,
+						   UNIGRAF_CONFIG_CONNECTOR_NAME);
+	if (!unigraf_connector_name) {
+		unigraf_debug("No connector name configured, will autodetect.\n");
+		unigraf_connector_name = NULL;
+	}
 
-		cfg_error = NULL;
-		cfg_edid_name = g_key_file_get_string(igt_key_file, UNIGRAF_CONFIG_GROUP,
-						      UNIGRAF_CONFIG_EDID_NAME, &cfg_error);
-		if (cfg_error) {
-			unigraf_debug("No default EDID set, use IGT default.\n");
-			cfg_edid_name = NULL;
-		}
+	cfg_edid_name = igt_rc_get_string(UNIGRAF_CONFIG_GROUP,
+					  UNIGRAF_CONFIG_EDID_NAME);
+	if (!cfg_edid_name) {
+		unigraf_debug("No default EDID set, using IGT default.\n");
+		cfg_edid_name = NULL;
+	}
 
-		cfg_error = NULL;
-		unigraf_crc = g_key_file_get_boolean(igt_key_file, UNIGRAF_CONFIG_GROUP,
-						     UNIGRAF_CONFIG_USE_CRC_NAME, &cfg_error);
-		if (cfg_error) {
-			unigraf_debug("CRC usage not configured, using unigraf CRC.\n");
-			unigraf_crc = true;
-		}
+	if (!igt_rc_get_boolean(UNIGRAF_CONFIG_GROUP,
+				UNIGRAF_CONFIG_USE_CRC_NAME, &unigraf_crc)) {
+		unigraf_debug("CRC usage not configured, using unigraf CRC.\n");
+		unigraf_crc = true;
+	}
 
-		cfg_error = NULL;
-		unigraf_stream_count = g_key_file_get_integer(igt_key_file, UNIGRAF_CONFIG_GROUP,
-							      UNIGRAF_CONFIG_MST_STREAM_COUNT,
-							      &cfg_error);
-		if (cfg_error) {
-			unigraf_debug("MST usage not configured, using SST.\n");
-			unigraf_stream_count = 0;
-		}
+	if (!igt_rc_get_integer(UNIGRAF_CONFIG_GROUP,
+				UNIGRAF_CONFIG_MST_STREAM_COUNT,
+				&unigraf_stream_count)) {
+		unigraf_debug("MST usage not configured, using SST.\n");
+		unigraf_stream_count = 0;
 	}
 
 	unigraf_assert(TSIX_DEV_RescanDevices(0, TSI_DEVCAP_VIDEO_CAPTURE, 0));
-- 
2.55.0.679.g6767b8d81c-goog