[igt-dev] [PATCH v2 7/8] tests/fbdev: Add tests for accessing framebuffer near EOF

[Thomas Zimmermann]

Fbdev has some specific behavior when reading/writing near the EOF, which
the eof test checks. If at least one bytes has been written, the number
of bytes has to be returned, otherwise an error code (if any) has to be
returned, or otherwise 0 has to returned. Not all drivers get this right.

Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
---
 tests/fbdev.c | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 47 insertions(+), 1 deletion(-)

diff --git a/tests/fbdev.c b/tests/fbdev.c
index d9f2e664..5b7086d1 100644
--- a/tests/fbdev.c
+++ b/tests/fbdev.c
@@ -79,7 +79,8 @@ static void framebuffer_tests(int fd)
 			   PROT_WRITE, MAP_SHARED, fd, 0);
 		igt_assert(map != MAP_FAILED);
 
-		buf = malloc(fix_info.smem_len);
+		/* allocate two additional bytes for eof test */
+		buf = malloc(fix_info.smem_len + 2);
 		igt_assert(buf);
 
 		ret = sysconf(_SC_PAGESIZE);
@@ -189,6 +190,51 @@ static void framebuffer_tests(int fd)
 		igt_require_f(pos, "found 0x55 at pos %zu, none expected\n", pos - map);
 	}
 
+	igt_subtest("eof") {
+		unsigned long lastindex = fix_info.smem_len - 1;
+		unsigned char *maplast = &((unsigned char *)map)[lastindex];
+		unsigned char *buflast = &((unsigned char *)buf)[lastindex];
+		ssize_t ret;
+
+		igt_describe("Check framebuffer access near EOF");
+
+		*buflast = 0x55;
+
+		/* write across EOF; set remaining bytes */
+		ret = pwrite(fd, buflast, 2, lastindex);
+		igt_require_f(ret == 1, "write crossed EOF, ret=%zd\n", ret);
+		igt_require_f(*maplast == *buflast, "write buffer differs from mapped framebuffer at final byte, "
+		                                    "maplast=%u buflast=%u\n", *maplast, *buflast);
+
+		/* write at EOF; get ENOSPC */
+		ret = pwrite(fd, &buflast[1], 1, lastindex + 1);
+		igt_require_f((ret == -1) && (errno == ENOSPC), "write at EOF, ret=%zd\n", ret);
+
+		*maplast = 0;
+
+		/* write final byte */
+		ret = pwrite(fd, buflast, 1, lastindex);
+		igt_require_f(ret == 1, "write before EOF, ret=%zd\n", ret);
+		igt_require_f(*maplast == *buflast, "write buffer differs from mapped framebuffer at final byte, "
+		                                    "maplast=%u buflast=%u\n", *maplast, *buflast);
+
+		/* write after EOF; get EFBIG */
+		ret = pwrite(fd, &buflast[2], 1, lastindex + 2);
+		igt_require_f((ret == -1) && (errno == EFBIG), "write after EOF, ret=%zd\n", ret);
+
+		*maplast = 0;
+
+		/* read across the EOF; get remaining bytes */
+		ret = pread(fd, buflast, 2, lastindex);
+		igt_require_f(ret == 1, "read before EOF, ret=%zd\n", ret);
+		igt_require_f(*maplast == *buflast, "read buffer differs from mapped framebuffer at final byte, "
+		                                    "maplast=%u buflast=%u\n", *maplast, *buflast);
+
+		/* read after EOF; get 0 */
+		ret = pread(fd, &buflast[1], 1, lastindex + 1);
+		igt_require_f(ret == 0, "read at EOF, ret=%zd\n", ret);
+	}
+
 	igt_fixture {
 		free(buf);
 		memset(map, 0, fix_info.smem_len); // don't leave garbage on the screen
-- 
2.29.0