tests/prime: test dma-buf llseek support

This exercises a proposed patch from Christopher James Halse Rogers.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

lib/drmtest.c

@@ -609,6 +609,16 @@ uint32_t prime_fd_to_handle(int fd, int dma_buf_fd)
 	return args.handle;
 }
 
+off_t prime_get_size(int dma_buf_fd)
+{
+	off_t ret;
+	ret = lseek(dma_buf_fd, 0, SEEK_END);
+	igt_assert(ret >= 0 || errno == ESPIPE);
+	igt_require(ret >= 0);
+
+	return ret;
+}
+
 /* signal interrupt helpers */
 static pid_t signal_helper = -1;
 long long int sig_stat;

lib/drmtest.h

@@ -85,6 +85,7 @@ int gem_available_fences(int fd);
 /* prime */
 int prime_handle_to_fd(int fd, uint32_t handle);
 uint32_t prime_fd_to_handle(int fd, int dma_buf_fd);
+off_t prime_get_size(int dma_buf_fd);
 
 /* generally useful helpers */
 void igt_fork_signal_helper(void);