prime_mmap: Add basic tests to write in a bo using CPU

This patch adds test_correct_cpu_write, which maps the texture buffer through a
prime fd and then writes directly to it using the CPU. It stresses the driver
to guarantee cache synchronization among the different domains.

This test also adds test_forked_cpu_write, which creates the GEM bo in one
process and pass the prime handle of the it to another process, which in turn
uses the handle only to map and write. Roughly speaking this test simulates
Chrome OS  architecture, where the Web content ("unpriviledged process") maps
and CPU-draws a buffer, which was previously allocated in the GPU process
("priviledged process").

This requires kernel modifications (Daniel Thompson's "drm: prime: Honour
O_RDWR during prime-handle-to-fd") and therefore prime_handle_to_fd_for_mmap is
added to fail in case these lack. Also, upcoming tests (e.g. next patch) are
going to use it as well, so make it public and available in the lib.

v2: adds prime_handle_to_fd_with_mmap for skipping test in older kernels and
test for invalid flags.

Signed-off-by: Tiago Vignatti <tiago.vignatti@intel.com>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/lib/ioctl_wrappers.c b/lib/ioctl_wrappers.c
index 7cc24ba3..171f5261 100644
--- a/lib/ioctl_wrappers.c
+++ b/lib/ioctl_wrappers.c
@@ -1422,6 +1422,31 @@ int prime_handle_to_fd(int fd, uint32_t handle)
 }
 
 /**
+ * prime_handle_to_fd_for_mmap:
+ * @fd: open i915 drm file descriptor
+ * @handle: file-private gem buffer object handle
+ *
+ * Same as prime_handle_to_fd above but with DRM_RDWR capabilities, which can
+ * be useful for writing into the mmap'ed dma-buf file-descriptor.
+ *
+ * Returns: The created dma-buf fd handle or -1 if the ioctl fails.
+ */
+int prime_handle_to_fd_for_mmap(int fd, uint32_t handle)
+{
+	struct drm_prime_handle args;
+
+	memset(&args, 0, sizeof(args));
+	args.handle = handle;
+	args.flags = DRM_CLOEXEC | DRM_RDWR;
+	args.fd = -1;
+
+	if (drmIoctl(fd, DRM_IOCTL_PRIME_HANDLE_TO_FD, &args) != 0)
+		return -1;
+
+	return args.fd;
+}
+
+/**
  * prime_fd_to_handle:
  * @fd: open i915 drm file descriptor
  * @dma_buf_fd: dma-buf fd handle