Hi Am 16.07.21 um 11:55 schrieb ainux.wang@xxxxxxxxx:
From: "Ainux.Wang" <ainux.wang@xxxxxxxxx> There is should a status when do not get edid.
Well, not really.So, the problem is that VGA is not hotplug-able. It's supposed to be connected when the computer gets switched on. And there's no interface for sensing the connection state.
But in practice, the cable can be attached/detached at any time. Reading out the EDID is the non-official way for detecting the connection state. You either get EDID data or garbage, where the latter is interpreted as 'disconnected'.
But really old monitors (maybe mid-90s and before) don't provide EDID data. For those, DRM adds standard VGA modes IIRC. And they would likely be detected as 'disconnected'.
I'll merge your original patch '(r <= 0)' and anyone who's stuck with such an old monitor can probably specify a compatible EDID on the kernel command line.
(I'd like to hear other people's opinion about this TBH.) Best regards Thomas
Signed-off-by: Ainux.Wang <ainux.wang@xxxxxxxxx>
---
drivers/gpu/drm/ast/ast_mode.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
index e5996ae03c49..05df48b3d223 100644
--- a/drivers/gpu/drm/ast/ast_mode.c
+++ b/drivers/gpu/drm/ast/ast_mode.c
@@ -1231,8 +1231,10 @@ static int ast_get_modes(struct drm_connector *connector)
ret = drm_add_edid_modes(connector, edid);
kfree(edid);
return ret;
- } else
+ } else {
drm_connector_update_edid_property(&ast_connector->base, NULL);
+ return -ENXIO;
+ }
return 0;
}
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Felix Imendörffer
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