On Fri, Oct 21, 2016 at 02:42:12PM +0100, Chris Wilson wrote:
> After hotplug notification, userspace has to reprobe all connectors to
> detect any changes. This can be expensive (some outputs may require time
> consuming load detection, some outputs may simply be slow to respond)
> and not all outputs need to be checked everytime. The kernel is usually
> in a very good position to know which outputs need to be reprobed (since
> it has just responded to the hardware notification) and can convey this
> information to userspace by tracking the timestamp of the last connector
> change onto the GETCONNECTOR query.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> Adding an epoch/timestamp field would look something like this. There are
> probably a few more places where the hardware indicates a real change
> (more than just status).
>
> That update_timestamp() should probably be
> atomic64_set(×tamp, ktime_get_ns());
> ---
> drivers/gpu/drm/drm_connector.c | 4 +++-
> drivers/gpu/drm/drm_crtc.c | 4 +++-
> drivers/gpu/drm/drm_probe_helper.c | 6 +++++-
> drivers/gpu/drm/gma500/mdfld_dsi_dpi.c | 1 +
> drivers/gpu/drm/gma500/mdfld_dsi_output.c | 1 +
> drivers/gpu/drm/i915/intel_dp.c | 4 ++++
> drivers/gpu/drm/i915/intel_dp_mst.c | 2 ++
> drivers/gpu/drm/i915/intel_hotplug.c | 5 ++++-
> drivers/gpu/drm/i915/intel_lvds.c | 1 +
> drivers/gpu/drm/nouveau/nouveau_connector.c | 1 +
> drivers/gpu/drm/vmwgfx/vmwgfx_ldu.c | 1 +
> drivers/gpu/drm/vmwgfx/vmwgfx_scrn.c | 1 +
> drivers/gpu/drm/vmwgfx/vmwgfx_stdu.c | 1 +
> include/drm/drm_connector.h | 8 ++++++++
> include/uapi/drm/drm.h | 2 +-
> include/uapi/drm/drm_mode.h | 26 ++++++++++++++++++++++++++
> 16 files changed, 63 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 2db7fb510b6c..cd3d85e94b91 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -227,6 +227,7 @@ int drm_connector_init(struct drm_device *dev,
> INIT_LIST_HEAD(&connector->modes);
> connector->edid_blob_ptr = NULL;
> connector->status = connector_status_unknown;
> + drm_connector_update_timestamp(connector);
>
> drm_connector_get_cmdline_mode(connector);
>
> @@ -1010,7 +1011,7 @@ static bool drm_mode_expose_to_userspace(const struct drm_display_mode *mode,
> int drm_mode_getconnector(struct drm_device *dev, void *data,
> struct drm_file *file_priv)
> {
> - struct drm_mode_get_connector *out_resp = data;
> + struct drm_mode_get_connector_v2 *out_resp = data;
> struct drm_connector *connector;
> struct drm_encoder *encoder;
> struct drm_display_mode *mode;
> @@ -1058,6 +1059,7 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
> out_resp->mm_height = connector->display_info.height_mm;
> out_resp->subpixel = connector->display_info.subpixel_order;
> out_resp->connection = connector->status;
> + out_resp->timestamp = ktime_to_ns(connector->timestamp);
Is there benefit to making it a timestamp as opposed to just an
incrementing counter?
--
Ville Syrjälä
Intel OTC
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