drm/bochs: add edid present check

Check header before trying to read the complete edid blob, to avoid the
log being spammed in case qemu has no edid support (old qemu or edid
support turned off).

Fixes: 01f23459cf drm/bochs: add edid support.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20181220101122.16153-1-kraxel@redhat.com

diff --git a/drivers/gpu/drm/bochs/bochs_hw.c b/drivers/gpu/drm/bochs/bochs_hw.c
index c90a0d492fd5973fe53f0430919e0fa8f2883368..d0b4e1cee83e8ddd7b1596190986eaf2a1148f79 100644 (file)
--- a/drivers/gpu/drm/bochs/bochs_hw.c
+++ b/drivers/gpu/drm/bochs/bochs_hw.c
@@ -86,9 +86,16 @@ static int bochs_get_edid_block(void *data, u8 *buf,
 
 int bochs_hw_load_edid(struct bochs_device *bochs)
 {
+       u8 header[8];
+
        if (!bochs->mmio)
                return -1;
 
+       /* check header to detect whenever edid support is enabled in qemu */
+       bochs_get_edid_block(bochs, header, 0, ARRAY_SIZE(header));
+       if (drm_edid_header_is_valid(header) != 8)
+               return -1;
+
        kfree(bochs->edid);
        bochs->edid = drm_do_get_edid(&bochs->connector,
                                      bochs_get_edid_block, bochs);