linux-kernel - [PATCH v3] drm/bochs: add edid present check

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Date:   Thu, 20 Dec 2018 11:11:21 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     andr2000@...il.com, daniel.vetter@...ll.ch,
        Gerd Hoffmann <kraxel@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        virtualization@...ts.linux-foundation.org (open list:DRM DRIVER FOR
        BOCHS VIRTUAL GPU), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v3] 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@...hat.com>
---
 drivers/gpu/drm/bochs/bochs_hw.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/bochs/bochs_hw.c b/drivers/gpu/drm/bochs/bochs_hw.c
index c90a0d492f..d0b4e1cee8 100644
--- 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);
-- 
2.9.3