On Mon, 30 Nov 2020 16:26:12 +0000
Simon Ser <contact@xxxxxxxxxxx> wrote:
> It seems like we can't have nice things, so let's just document the
> disappointing behaviour instead.
>
> The previous version assumed the kernel would perform the probing work
> when appropriate, however this is not the case today. Update the
> documentation to reflect reality.
Hi Simon,
yeah, this message actually explains something. Good.
> v2:
>
> - Improve commit message to explain why this change is made (Pekka)
> - Keep the bit about flickering (Daniel)
> - Explain when user-space should force-probe, and when it shouldn't (Daniel)
>
> Signed-off-by: Simon Ser <contact@xxxxxxxxxxx>
> Fixes: 2ac5ef3b2362 ("drm: document drm_mode_get_connector")
> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Cc: Pekka Paalanen <ppaalanen@xxxxxxxxx>
> Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
> include/uapi/drm/drm_mode.h | 13 +++++--------
> 1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index b49fbf2bdc40..1c064627e6c3 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -414,15 +414,12 @@ enum drm_mode_subconnector {
> *
> * If the @count_modes field is set to zero, the kernel will perform a forced
> * probe on the connector to refresh the connector status, modes and EDID.
> - * A forced-probe can be slow and the ioctl will block. A force-probe can cause
> - * flickering and temporary freezes, so it should not be performed
> - * automatically.
> + * A forced-probe can be slow, might cause flickering and the ioctl will block.
> *
> - * User-space shouldn't need to force-probe connectors in general: the kernel
> - * will automatically take care of probing connectors that don't support
> - * hot-plug detection when appropriate. However, user-space may force-probe
> - * connectors on user request (e.g. clicking a "Scan connectors" button, or
> - * opening a UI to manage screens).
> + * User-space needs to force-probe connectors to ensure their metadata is
> + * up-to-date at startup and after receiving a hot-plug event. User-space
> + * may perform a forced-probe when the user explicitly requests it. User-space
> + * shouldn't perform a forced-probe in other situations.
> */
> struct drm_mode_get_connector {
> /** @encoders_ptr: Pointer to ``__u32`` array of object IDs. */
Sounds good, err... accurate to me.
Reviewed-by: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx>
Thanks,
pq
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