On Mon, Jul 24, 2017 at 05:54:46PM +0300, Paul Kocialkowski wrote:
> This adds a common drm helper to detect whether the EDID changed from
> the last known cached one. This is useful help detect that a monitor was
> changed during a suspend/resume cycle.
>
> When that happens (a monitor is replaced by another one during suspend),
> no hotplug event will be triggered so the change will not be caught at
> resume time. Detecting that the EDID changed allows detecting it.
>
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@xxxxxxxxxxxxxxx>
I can't find the older mails I've typed about this, but the plan we've
discussed a while back was:
- Add a generational counter to each connector, maybe even expose it to
userspace.
- Increment that counter every time something changed, e.g.
connector->status in the propbe helpers, or when attaching a new edid
with the set_edid helper.
- Tada, no changes needed to drivers, and easily extensible to other
things than edid!
Cheers, Daniel
> ---
> drivers/gpu/drm/drm_edid.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
> include/drm/drm_edid.h | 3 +++
> 2 files changed, 48 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 6bb6337be920..f6ce8bc2907a 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -5036,3 +5036,48 @@ static void drm_get_displayid(struct drm_connector *connector,
> }
> return;
> }
> +
> +/**
> + * drm_check_edid_changed - Check whether the EDID changed since the last update
> + * @connector: connector we're probing
> + * @adapter: I2C adapter to use for DDC
> + *
> + * Check whether the EDID changed since the last time it was updated in the
> + * drm blob cache.
> + *
> + * Return: A boolean indicating whether a change happened or not.
> + */
> +bool drm_check_edid_changed(struct drm_connector *connector,
> + struct i2c_adapter *adapter)
> +{
> + struct drm_property_blob *edid_blob;
> + struct edid *edid_stored;
> + struct edid *edid_read;
> + int ret = 0;
> +
> + if (!connector->edid_blob_ptr)
> + return false;
> +
> + edid_blob = drm_property_blob_get(connector->edid_blob_ptr);
> + if (!edid_blob)
> + return false;
> +
> + if (!edid_blob->data || edid_blob->length != sizeof(struct edid))
> + goto out;
> +
> + edid_stored = (struct edid *) edid_blob->data;
> +
> + edid_read = drm_get_edid(connector, adapter);
> + if (!edid_read)
> + goto out;
> +
> + ret = memcmp(edid_stored, edid_read, sizeof(struct edid));
> +
> + kfree(edid_read);
> +
> +out:
> + drm_property_blob_put(edid_blob);
> +
> + return ret != 0;
> +}
> +EXPORT_SYMBOL_GPL(drm_check_edid_changed);
> diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
> index 1e1908a6b1d6..593a97b269c3 100644
> --- a/include/drm/drm_edid.h
> +++ b/include/drm/drm_edid.h
> @@ -485,4 +485,7 @@ void drm_edid_get_monitor_name(struct edid *edid, char *name,
> struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev,
> int hsize, int vsize, int fresh,
> bool rb);
> +bool drm_check_edid_changed(struct drm_connector *connector,
> + struct i2c_adapter *adapter);
> +
> #endif /* __DRM_EDID_H__ */
> --
> 2.13.2
>
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> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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