Hi, On Fri, 2019-05-10 at 16:54 +0200, Daniel Vetter wrote: > On Fri, May 10, 2019 at 2:12 PM Paul Kocialkowski > <paul.kocialkowski@xxxxxxxxxxx> wrote: > > Hi, > > > > On Tue, 2019-05-07 at 21:57 +0530, Ramalingam C wrote: > > > DRM API for generating uevent for a status changes of connector's > > > property. > > > > > > This uevent will have following details related to the status change: > > > > > > HOTPLUG=1, CONNECTOR=<connector_id> and PROPERTY=<property_id> > > > > > > Need ACK from this uevent from userspace consumer. > > > > So we just had some discussions over on IRC and at about the hotplug > > issue and came up with similar ideas: > > https://lists.freedesktop.org/archives/dri-devel/2019-May/217408.html > > > > The conclusions of these discussions so far would be to have a more or > > less fine grain of uevent reporting depending on what happened. The > > point is that we need to cover different cases: > > - one or more properties changed; > > - the connector status changed; > > - something else about the connector changed (e.g. EDID/modes) > > > > For the first case, we can send out: > > HOTPLUG=1 > > CONNECTOR=<id> > > PROPERTY=<id> > > > > and no reprobe is required. > > > > For the second one, something like: > > HOTPLUG=1 > > CONNECTOR=<id> > > STATUS=Connected/Disconnected > > > > and a connector probe is needed for connected, but not for > > disconnected; > > > > For the third one, we can only indicate the connector: > > HOTPLUG=1 > > CONNECTOR=<id> > > > > and a reprobe of the connector is always needed > > There's no material difference between this one and the previous one. > Plus there's no beenfit in supplying the actual value of the property, > i.e. we can reuse the same PROPERTY=<id-of-status-property> trick. That's the idea, but we need to handle status changes differently than properties, since as far as I know, connected/unconnected status is not exposed as a prop for the connector. > Here's why: > - A side effect of forcing a probe on a connector is that you get to > read all the properties, so supplying them is kinda pointless. Agreed, except for the status case where it's useful to know it's a disconnect, because we don't need any probe step in that case. > - You can read STATUS without forcing a reprobe, if you want to avoid > the reprobe for disconnected. I'd kinda not recommend that though, > feels a bit like overoptimizing. And for reasonable connectors (i.e. > dp) reprobing a disconnected output is fast. HDMI is ... less > reasonable unfortunately, but oh well. How would that be retreived then? From the looks of it, that's a MODE_GETCONNECTOR ioctl and I was under the impression this is what does the full reprobe. Not sure what issues could arise in case of disconnect without reprobe -- at least I don't see why userspace should have to do anything in particular except no longer using the connector, even in complex DP MST cases. > - There's no way to only reprobe status, you can only ever reprobe > everything with the current ioctl and implementations. Having an > option to reprobe only parts of it doesn't seem useful to me (we need > to read the EDID anyway, and that's the expensive part of reprobing in > almost all cases). Agreed. > In a way PROPERTY=<status-prop-id> simply tells userspace that it > needs to reprobe this connector. I thought we could access the props alone, which avoids doing a reprobe when the kernel knows that only a prop or a set of props changed and do not require a full reprobe. That's the first case I was mentionning. > At that point we need to figure out whether this is a good uapi or > not, and that's where the epoch comes in. There's two reasons for an > epoch: > - We need it internally because I'm not goinig to wire a new return > value through hundreds of connector probe functions. It's much easier > to have an epoch counter which we set from e.g. drm_set_edid and > similar functions that update probe state. I don't think I'm following what issue this is trying to solve internally. > - If userspace misses an event and there's no epoch, we're forcing > userspace to reprobe everything. Use case would be if a compositor is > switched away we probably don't want to piss of the current compositor > by blocking it's own probe kernel calls by doing our own (probe is > single-threaded in the kernel through the dev->mode_config.mutex). If > it can read the epoch property (which it can do without forcing a > reprobe) userspace would know which connectors it needs to check and > reprobe. > > Hence why epoch, it's a bit more robust userspace api. Ofc you could > also require that userspace needs to keep parsing all uevents and make > a list of all connectors it needs to reprobe when it's back to being > the active compositor. But just comparing a current epoch with the one > you cached from the last full probe is much easier. Fair enough, I think it's a fine idea for robustness yes, but I think we could also provide extra info in the uevent when relevant and not rely on that entirely. > Another thing: None of this we can for connectors with unreliable hdp. > Or at least you'll piss of users if you cache always. The sad thing is > that HDMI is unreliable, at least on some machines/screen combos (you > never get a hpd irq if you plug in/unplug). So real compositors still > need to reprobe when the user asks for it. igt can probably get away > without reprobing. I wonder how that is handled currently and how a user action can solve the issue without any notification from the kernel. Maybe a need a better understanding of that case to have a clearer idea. Cheers, Paul > -Daniel > > > Then we still have the legacy case: > > HOTPLUG=1 > > > > where userspace is expected to reprobe all the connectors. > > > > I think this would deserve to be a separate series on its own. So I am > > proposing to take this one off your plate and come up with another > > seres implementing this proposal. What do you think? > > > > Cheers, > > > > Paul > > > > > v2: > > > Minor fixes at KDoc comments [Daniel] > > > v3: > > > Check the property is really attached with connector [Daniel] > > > > > > Signed-off-by: Ramalingam C <ramalingam.c@xxxxxxxxx> > > > Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > > > --- > > > drivers/gpu/drm/drm_sysfs.c | 35 +++++++++++++++++++++++++++++++++++ > > > include/drm/drm_sysfs.h | 5 ++++- > > > 2 files changed, 39 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c > > > index 18b1ac442997..63fa951a20db 100644 > > > --- a/drivers/gpu/drm/drm_sysfs.c > > > +++ b/drivers/gpu/drm/drm_sysfs.c > > > @@ -21,6 +21,7 @@ > > > #include <drm/drm_sysfs.h> > > > #include <drm/drmP.h> > > > #include "drm_internal.h" > > > +#include "drm_crtc_internal.h" > > > > > > #define to_drm_minor(d) dev_get_drvdata(d) > > > #define to_drm_connector(d) dev_get_drvdata(d) > > > @@ -320,6 +321,9 @@ void drm_sysfs_lease_event(struct drm_device *dev) > > > * Send a uevent for the DRM device specified by @dev. Currently we only > > > * set HOTPLUG=1 in the uevent environment, but this could be expanded to > > > * deal with other types of events. > > > + * > > > + * Any new uapi should be using the drm_sysfs_connector_status_event() > > > + * for uevents on connector status change. > > > */ > > > void drm_sysfs_hotplug_event(struct drm_device *dev) > > > { > > > @@ -332,6 +336,37 @@ void drm_sysfs_hotplug_event(struct drm_device *dev) > > > } > > > EXPORT_SYMBOL(drm_sysfs_hotplug_event); > > > > > > +/** > > > + * drm_sysfs_connector_status_event - generate a DRM uevent for connector > > > + * property status change > > > + * @connector: connector on which property status changed > > > + * @property: connector property whoes status changed. > > > + * > > > + * Send a uevent for the DRM device specified by @dev. Currently we > > > + * set HOTPLUG=1 and connector id along with the attached property id > > > + * related to the status change. > > > + */ > > > +void drm_sysfs_connector_status_event(struct drm_connector *connector, > > > + struct drm_property *property) > > > +{ > > > + struct drm_device *dev = connector->dev; > > > + char hotplug_str[] = "HOTPLUG=1", conn_id[30], prop_id[30]; > > > + char *envp[4] = { hotplug_str, conn_id, prop_id, NULL }; > > > + > > > + WARN_ON(!drm_mode_obj_find_prop_id(&connector->base, > > > + property->base.id)); > > > + > > > + snprintf(conn_id, ARRAY_SIZE(conn_id), > > > + "CONNECTOR=%u", connector->base.id); > > > + snprintf(prop_id, ARRAY_SIZE(prop_id), > > > + "PROPERTY=%u", property->base.id); > > > + > > > + DRM_DEBUG("generating connector status event\n"); > > > + > > > + kobject_uevent_env(&dev->primary->kdev->kobj, KOBJ_CHANGE, envp); > > > +} > > > +EXPORT_SYMBOL(drm_sysfs_connector_status_event); > > > + > > > static void drm_sysfs_release(struct device *dev) > > > { > > > kfree(dev); > > > diff --git a/include/drm/drm_sysfs.h b/include/drm/drm_sysfs.h > > > index 4f311e836cdc..d454ef617b2c 100644 > > > --- a/include/drm/drm_sysfs.h > > > +++ b/include/drm/drm_sysfs.h > > > @@ -4,10 +4,13 @@ > > > > > > struct drm_device; > > > struct device; > > > +struct drm_connector; > > > +struct drm_property; > > > > > > int drm_class_device_register(struct device *dev); > > > void drm_class_device_unregister(struct device *dev); > > > > > > void drm_sysfs_hotplug_event(struct drm_device *dev); > > > - > > > +void drm_sysfs_connector_status_event(struct drm_connector *connector, > > > + struct drm_property *property); > > > #endif > > -- > > Paul Kocialkowski, Bootlin > > Embedded Linux and kernel engineering > > https://bootlin.com > > > > -- Paul Kocialkowski, Bootlin Embedded Linux and kernel engineering https://bootlin.com _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
