[Intel-gfx] [PATCH i-g-t v2] Add support for forcing a specific driver

[Petri Latvala]

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

v2 (Petri):
 - Use an environment variable instead of command line
 - Refactor the loop in __open_device
 - Don't try to load kernel modules

Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo at gmail.com>
Signed-off-by: Petri Latvala <petri.latvala at intel.com>
Cc: Arkadiusz Hiler <arkadiusz.hiler at intel.com>
Cc: gustavo at padovan.org
---

Did the changes I suggested myself to see what else is lurking
there. I'm still unsure whether using IGT_FORCE_DRIVER=something
should still accept opening e.g. an i915 device with DRIVER_INTEL,
currently this does. Both ways have their merits.

I was able to test vkms with this patch, revealing some amount of
intelisms still lurking.


 lib/drmtest.c  | 35 +++++++++++++++++++++++++++++++++++
 lib/drmtest.h  |  2 ++
 lib/igt_core.c |  5 +++++
 3 files changed, 42 insertions(+)

diff --git a/lib/drmtest.c b/lib/drmtest.c
index fae6f86f..e8308b0d 100644
--- a/lib/drmtest.c
+++ b/lib/drmtest.c
@@ -146,6 +146,31 @@ 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 (!name)
+		igt_warn("No driver specified, keep default behaviour");
+
+	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:
@@ -229,6 +254,16 @@ static int __open_device(const char *base, int offset, unsigned int chipset)
 		if (fd == -1)
 			continue;
 
+		// Force options
+		if (chipset == DRIVER_ANY && forced_driver()) {
+			if (__is_device(fd, forced_driver())) {
+				igt_debug("Force option used: Using driver %s\n", forced_driver());
+				return fd;
+			}
+
+			continue;
+		}
+
 		if (chipset & DRIVER_INTEL && is_i915_device(fd) &&
 		    has_known_intel_chipset(fd))
 			return fd;
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 c52c0818..c17e53c5 100644
--- a/lib/igt_core.c
+++ b/lib/igt_core.c
@@ -646,6 +646,11 @@ 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,
-- 
2.14.1