[igt-dev] [PATCH i-g-t v3] lib/i915/gem_mman: Add a helper for obtaining mappable aperture version

[Janusz Krzysztofik]

From: Janusz Krzysztofik <janusz.krzysztofik at intel.com>

If a test calls a function which depends on availabiblity of a
supported mappable aperture, an error may be reported by the kernel on
unsupported hardware.  That may negatively affect results reported by a
test framework even if that test ignores the failure and succeedes.

This helper wraps an IOCTL call which returns a version number of a
mappable aperture.  It may be used by tests which need to adjust their
scope depending on availability of specific version of mappable
aperture.

Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at intel.com>
Cc: Antonio Argenziano <antonio.argenziano at intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
---
Changelog:
v2 (internal) -> v3:
- make the code less obsucre, more explicit (Antonio),
- reword the helper documentation and commit message.

v1 (internal) -> v2 (internal):
- minimize future potential conflicts with 
  https://patchwork.freedesktop.org/patch/294053/?series=58551&rev=1
  (no progress with than one so not waiting for it any longer):
  - convert the helper to a drop-in replacement of the one from the
    above mentioned patch, returning mappable aperture version, not
    only information on its availability,
  - drop any other wrappers,
- document the helper,
- reword commit message.

 lib/i915/gem_mman.c | 22 ++++++++++++++++++++++
 lib/i915/gem_mman.h |  1 +
 2 files changed, 23 insertions(+)

diff --git a/lib/i915/gem_mman.c b/lib/i915/gem_mman.c
index 3cf9a6bb..3a3f3e5c 100644
--- a/lib/i915/gem_mman.c
+++ b/lib/i915/gem_mman.c
@@ -40,6 +40,28 @@
 #define VG(x) do {} while (0)
 #endif
 
+/**
+ * gem_mmap__gtt_version:
+ * @fd: open i915 drm file descriptor
+ *
+ * This functions wraps up an IOCTL to obtain mappable aperture version.
+ *
+ * Returns: mappable aperture version, -1 on failure.
+ */
+int gem_mmap__gtt_version(int fd)
+{
+	int gtt_version, ret;
+	struct drm_i915_getparam gp = {
+		.param = I915_PARAM_MMAP_GTT_VERSION,
+		.value = &gtt_version,
+	};
+
+	ret = ioctl(fd, DRM_IOCTL_I915_GETPARAM, &gp);
+	if (ret == 0)
+		ret = gtt_version;
+	return ret;
+}
+
 /**
  * __gem_mmap__gtt:
  * @fd: open i915 drm file descriptor
diff --git a/lib/i915/gem_mman.h b/lib/i915/gem_mman.h
index f7242ed7..ab12e566 100644
--- a/lib/i915/gem_mman.h
+++ b/lib/i915/gem_mman.h
@@ -25,6 +25,7 @@
 #ifndef GEM_MMAN_H
 #define GEM_MMAN_H
 
+int gem_mmap__gtt_version(int fd);
 void *gem_mmap__gtt(int fd, uint32_t handle, uint64_t size, unsigned prot);
 void *gem_mmap__cpu(int fd, uint32_t handle, uint64_t offset, uint64_t size, unsigned prot);
 
-- 
2.21.0