[PATCH i-g-t v2] Add support for forcing specific module

[Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx>]

This commit adds a new option for forcing the use of a specific driver
indicated via an environment variable.

Changes since V1:
 Petri:
 - Use an environment variable instead of command line
 - Refactor the loop in __search_and_open to accept forced module
 - Don't try to load kernel modules

Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx>
---
 lib/drmtest.c  | 44 ++++++++++++++++++++++++++++++++++++++++++--
 lib/drmtest.h  |  2 ++
 lib/igt_core.c |  5 +++++
 3 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/lib/drmtest.c b/lib/drmtest.c
index bfa2e0f0..6e35d1be 100644
--- a/lib/drmtest.c
+++ b/lib/drmtest.c
@@ -123,6 +123,36 @@ static bool has_known_intel_chipset(int fd)
 	return true;
 }
 
+static char _forced_driver[5] = "";
+
+/**
+ * __set_forced_driver:
+ * @name: name of driver to forcibly use
+ *
+ * Set the name of a driver to use when calling #drm_open_driver with
+ * the #DRIVER_ANY flag.
+ */
+void __set_forced_driver(const char *name)
+{
+	if (!strcmp(name, "")) {
+		igt_warn("IGT_FORCE_DRIVER flag specified without a value,"
+			 "ignoring force option\n");
+		return;
+	}
+
+	igt_info("Attempt to force module %s\n", name);
+
+	strncpy(_forced_driver, name, 4);
+}
+
+static const char *forced_driver(void)
+{
+	if (_forced_driver[0])
+		return _forced_driver;
+
+	return NULL;
+}
+
 #define LOCAL_I915_EXEC_VEBOX	(4 << 0)
 /**
  * gem_quiescent_gpu:
@@ -250,8 +280,18 @@ static int __search_and_open(const char *base, int offset, unsigned int chipset)
 
 		sprintf(name, "%s%u", base, i + offset);
 		fd = open_device(name, chipset);
-		if (fd != -1)
-			return fd;
+		if (fd == -1)
+			continue;
+
+		// Force module
+		if (chipset == DRIVER_ANY && forced_driver()) {
+			if (__is_device(fd, forced_driver()))
+				return fd;
+			close(fd);
+			continue;
+		}
+
+		return fd;
 	}
 
 	return -1;
diff --git a/lib/drmtest.h b/lib/drmtest.h
index 949865ee..62f53ec3 100644
--- a/lib/drmtest.h
+++ b/lib/drmtest.h
@@ -51,6 +51,8 @@
  */
 #define DRIVER_ANY 	~(DRIVER_VGEM)
 
+void __set_forced_driver(const char *name);
+
 /**
  * ARRAY_SIZE:
  * @arr: static array
diff --git a/lib/igt_core.c b/lib/igt_core.c
index 23bb858f..8e65b5e3 100644
--- a/lib/igt_core.c
+++ b/lib/igt_core.c
@@ -647,6 +647,11 @@ static void common_init_env(void)
 	igt_frame_dump_path = getenv("IGT_FRAME_DUMP_PATH");
 
 	stderr_needs_sentinel = getenv("IGT_SENTINEL_ON_STDERR") != NULL;
+
+	env = getenv("IGT_FORCE_DRIVER");
+	if (env) {
+		__set_forced_driver(env);
+	}
 }
 
 static int common_init(int *argc, char **argv,
-- 
2.18.0


-- 
Rodrigo Siqueira
http://siqueira.tech
Graduate Student
Department of Computer Science
University of São Paulo
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