[igt-dev] [RFT v4 3/6] igt/lib: Add wrapper to check if gtt mapping is available

[Antonio Argenziano]

Add wrapper to get mmap_gtt version number and another to check if
gtt mapping is at all available.

v2:
	- Check errno only after failed syscall. (Chris)

Cc: Katarzyna Dec <katarzyna.dec at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld at intel.com>
Signed-off-by: Antonio Argenziano <antonio.argenziano at intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
---
 lib/i915/gem_mman.c | 40 +++++++++++++++++++++++++++++++++++++++-
 lib/i915/gem_mman.h | 11 +++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/lib/i915/gem_mman.c b/lib/i915/gem_mman.c
index 429de912..4d41a66d 100644
--- a/lib/i915/gem_mman.c
+++ b/lib/i915/gem_mman.c
@@ -40,6 +40,41 @@
 #define VG(x) do {} while (0)
 #endif
 
+/**
+ * gem_mmap__gtt_version:
+ * @fd: open i915 drm file descriptor
+ *
+ * This wraps I915_PARAM_MMAP_GTT_VERSION. It will return the supported feature
+ * set for gtt mapping. Since the mappable aperture in not always present, this
+ * function will return '-1' in case there is none.
+ */
+static int gem_mmap__gtt_version(int fd)
+{
+	static int gtt_version = ~0;
+
+	if (gtt_version == ~0) {
+			struct drm_i915_getparam gp;
+
+			gtt_version = 0;
+
+			memset(&gp, 0, sizeof(gp));
+			gp.param = I915_PARAM_MMAP_GTT_VERSION;
+			gp.value = &gtt_version;
+
+			if(ioctl(fd, DRM_IOCTL_I915_GETPARAM, &gp) && errno == -ENODEV)
+				gtt_version = -1; /* No mappable aperture */
+
+			errno = 0;
+	}
+
+	return gtt_version;
+}
+
+bool gem_mmap__has_gtt(int fd)
+{
+	return gem_mmap__gtt_version(fd) >= 0;
+}
+
 /**
  * __gem_mmap__gtt:
  * @fd: open i915 drm file descriptor
@@ -121,6 +156,9 @@ bool gem_mmap__has_wc(int fd)
 		int mmap_version = -1;
 		int gtt_version = -1;
 
+		bool compatible_gtt_version =
+			(!gem_mmap__has_gtt(fd) || gem_mmap__gtt_version(fd) >= 2);
+
 		memset(&gp, 0, sizeof(gp));
 		gp.param = I915_PARAM_MMAP_GTT_VERSION;
 		gp.value = &gtt_version;
@@ -132,7 +170,7 @@ bool gem_mmap__has_wc(int fd)
 		ioctl(fd, DRM_IOCTL_I915_GETPARAM, &gp);
 
 		/* Do we have the mmap_ioctl with DOMAIN_WC? */
-		if (mmap_version >= 1 && gtt_version >= 2) {
+		if (mmap_version >= 1 && compatible_gtt_version) {
 			struct drm_i915_gem_mmap arg;
 
 			/* Does this device support wc-mmaps ? */
diff --git a/lib/i915/gem_mman.h b/lib/i915/gem_mman.h
index fff2ecab..d13bffae 100644
--- a/lib/i915/gem_mman.h
+++ b/lib/i915/gem_mman.h
@@ -31,6 +31,8 @@ void *gem_mmap__cpu(int fd, uint32_t handle, uint64_t offset, uint64_t size, uns
 bool gem_mmap__has_wc(int fd);
 void *gem_mmap__wc(int fd, uint32_t handle, uint64_t offset, uint64_t size, unsigned prot);
 
+bool gem_mmap__has_gtt(int fd);
+
 #ifndef I915_GEM_DOMAIN_WC
 #define I915_GEM_DOMAIN_WC 0x80
 #endif
@@ -51,6 +53,15 @@ int gem_munmap(void *ptr, uint64_t size);
  */
 #define gem_require_mmap_wc(fd) igt_require(gem_mmap__has_wc(fd))
 
+/**
+ * gem_require_mmap_gtt:
+ * @fd: open i915 drm file descriptor
+ *
+ * Feature test macro to query whether memory mappings through the  mappable
+ * aperture are available. Automatically skips through igt_require() if not.
+ */
+#define gem_require_mmap_gtt(fd) igt_require(gem_mmap__has_gtt(fd))
+
 struct local_drm_i915_gem_mmap_offset {
 	/** Handle for the object being mapped. */
 	__u32 handle;
-- 
2.20.1