igt.cocci: check the return values of various functions

Add rules to fix unused-result warnings when compiling with
_FORTIFY_SOURCE defined and apply them to the library and tests.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Thomas Wood <thomas.wood@intel.com>

tests/kms_fbc_crc.c

@@ -198,7 +198,7 @@ static bool fbc_enabled(data_t *data)
 	status = igt_debugfs_fopen("i915_fbc_status", "r");
 	igt_assert(status);
 
-	fread(str, sizeof(str) - 1, 1, status);
+	igt_assert_eq(fread(str, sizeof(str) - 1, 1, status), 1);
 	fclose(status);
 	return strstr(str, "FBC enabled") != NULL;
 }
@@ -510,7 +510,7 @@ igt_main
 
 		status = igt_debugfs_fopen("i915_fbc_status", "r");
 		igt_require_f(status, "No i915_fbc_status found\n");
-		fread(buf, sizeof(buf), 1, status);
+		igt_assert_eq(fread(buf, sizeof(buf), 1, status), sizeof(buf));
 		fclose(status);
 		buf[sizeof(buf) - 1] = '\0';
 		igt_require_f(!strstr(buf, "unsupported by this chipset") &&

tests/kms_vblank.c

@@ -101,7 +101,7 @@ static void query(int fd, bool busy)
 		 busy ? "busy" : "idle", elapsed(&start, &end, count));
 
 	if (busy)
-		read(fd, buf, sizeof(buf));
+		igt_assert_eq(read(fd, buf, sizeof(buf)), sizeof(buf));
 }
 
 igt_main

tests/pm_lpsp.c

@@ -45,12 +45,12 @@ static void disable_audio_runtime_pm(void)
 
 	fd = open("/sys/module/snd_hda_intel/parameters/power_save", O_WRONLY);
 	if (fd >= 0) {
-		write(fd, "1\n", 2);
+		igt_assert_eq(write(fd, "1\n", 2), 2);
 		close(fd);
 	}
 	fd = open("/sys/bus/pci/devices/0000:00:03.0/power/control", O_WRONLY);
 	if (fd >= 0) {
-		write(fd, "auto\n", 5);
+		igt_assert_eq(write(fd, "auto\n", 5), 5);
 		close(fd);
 	}
 	/* Give some time for it to react. */

tests/prime_udl.c

@@ -61,7 +61,7 @@ static int find_and_open_devices(void)
 		if (!fl)
 			break;
 
-		fgets(vendor_id, 8, fl);
+		igt_assert_neq(fgets(vendor_id, 8, fl), NULL);
 		fclose(fl);
 
 		venid = strtoul(vendor_id, NULL, 16);