Hi Daniel,
On Wed, Aug 14, 2019 at 07:02:29PM +0200, Daniel Vetter wrote:
> On Wed, Aug 14, 2019 at 04:30:57PM +0300, Laurent Pinchart wrote:
> > On Wed, Aug 14, 2019 at 03:03:29PM +0200, Daniel Vetter wrote:
> >> On Thu, Aug 08, 2019 at 09:36:31PM +0300, Laurent Pinchart wrote:
> >>> On Thu, Aug 08, 2019 at 09:19:48PM +0300, Laurent Pinchart wrote:
> >>>> On Thu, Jul 11, 2019 at 09:35:48AM +0200, Daniel Vetter wrote:
> >>>>> On Wed, Jul 10, 2019 at 02:12:14PM +0200, Andrzej Hajda wrote:
> >>>>>> Hi Laurent,
> >>>>>>
> >>>>>> I like the approach, current practice when almost every bridge should
> >>>>>> optionally implement connector, or alternatively downstream bridge or
> >>>>>> panel is very painful.
> >>>>>
> >>>>> Yeah I think this looks mostly reasonable. Some api design comments on top
> >>>>> of Andrzej', with the fair warning that I didn't bother to read up on how
> >>>>> it's all used in the end. I probably should go and do that, at least to
> >>>>> get a feeling for what your hpd_cb usually does.
> >>>>>
> >>>>>> More comments inlined.
> >>>>>>
> >>>>>> On 07.07.2019 20:18, Laurent Pinchart wrote:
> >>>>>>> To support implementation of DRM connectors on top of DRM bridges
> >>>>>>> instead of by bridges, the drm_bridge needs to expose new operations and
> >>>>>>> data:
> >>>>>>>
> >>>>>>> - Output detection, hot-plug notification, mode retrieval and EDID
> >>>>>>> retrieval operations
> >>>>>>> - Bitmask of supported operations
> >>>>>>
> >>>>>>
> >>>>>> Why do we need these bitmask at all? Why cannot we rely on presence of
> >>>>>> operation's callback?
> >>>>>
> >>>>> Yeah also not a huge fan of these bitmasks. Smells like
> >>>>> DRIVER_GEM|DRIVER_MODESET, and I personally really hate those. Easy to
> >>>>> add, generally good excuse to not have to think through the design between
> >>>>> different parts of drivers - "just" add another flag.
> >>>>
> >>>> The reason is that a bridge may support an operation (as in implemented
> >>>> in the bridge hardware), but that operation may not be supported on a
> >>>> particular board. For instance an HDMI encoder may support reading EDID
> >>>> when the DDC lines are connected to the encoder, but a board may connect
> >>>> the DDC lines to an I2C port of the SoC. We thus need to decouple
> >>>> if a particular instance of the device supports the operation (exposed
> >>>> by the ops flags) from the function pointers.
> >>>>
> >>>> We could of course allocate the drm_bridge_funcs structure dynamically
> >>>> for each bridge instance, and fill it with function pointers manually,
> >>>> leaving the unused ops always NULL, but that would require making the
> >>>> structure writable, which is considered a security issue. That's why I
> >>>> decided to keep the drm_bridge_funcs structure as a global static const
> >>>> structure, and add an ops bitmask.
> >>>>
> >>>>>>> - Bridge output type
> >>>>>>>
> >>>>>>> Add and document these.
> >>>>>>>
> >>>>>>> Three new bridge helper functions are also added to handle hot plug
> >>>>>>> notification in a way that is as transparent as possible for the
> >>>>>>> bridges.
> >>>>>>
> >>>>>> Documentation of new opses does not explain how it should cooperate with
> >>>>>> bridge chaining, I suppose they should be chained explicitly, am I
> >>>>>> right? More comments about it later.
> >>>>
> >>>> No, the whole point is that they should not be chained at all. A bridge
> >>>> does not have to propagate, for instance, .get_edid() to the next
> >>>> bridge. That's one of the core design principles in this series, I want
> >>>> to keep the bridges as simple as possible, and move the complexity of
> >>>> the boilerplate code that is currently copied all around to helpers. See
> >>>> patch "drm: Add helper to create a connector for a chain of bridges" for
> >>>> more information about how this is used, with a helper that delegates
> >>>> the connector operations to the correct bridge in the chain based on the
> >>>> ops reported by each bridge.
> >>>>
> >>>>>>> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> >>>>>>> ---
> >>>>>>> drivers/gpu/drm/drm_bridge.c | 92 +++++++++++++++++++
> >>>>>>> include/drm/drm_bridge.h | 170 ++++++++++++++++++++++++++++++++++-
> >>>>>>> 2 files changed, 261 insertions(+), 1 deletion(-)
> >>>>>>>
> >>>>>>> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> >>>>>>> index 519577f363e3..3c2a255df7af 100644
> >>>>>>> --- a/drivers/gpu/drm/drm_bridge.c
> >>>>>>> +++ b/drivers/gpu/drm/drm_bridge.c
> >>>>>>> @@ -70,6 +70,8 @@ static LIST_HEAD(bridge_list);
> >>>>>>> */
> >>>>>>> void drm_bridge_add(struct drm_bridge *bridge)
> >>>>>>> {
> >>>>>>> + mutex_init(&bridge->hpd_mutex);
> >>>>>>> +
> >>>>>>> mutex_lock(&bridge_lock);
> >>>>>>> list_add_tail(&bridge->list, &bridge_list);
> >>>>>>> mutex_unlock(&bridge_lock);
> >>>>>>> @@ -86,6 +88,8 @@ void drm_bridge_remove(struct drm_bridge *bridge)
> >>>>>>> mutex_lock(&bridge_lock);
> >>>>>>> list_del_init(&bridge->list);
> >>>>>>> mutex_unlock(&bridge_lock);
> >>>>>>> +
> >>>>>>> + mutex_destroy(&bridge->hpd_mutex);
> >>>>>>> }
> >>>>>>> EXPORT_SYMBOL(drm_bridge_remove);
> >>>>>>>
> >>>>>>> @@ -463,6 +467,94 @@ void drm_atomic_bridge_enable(struct drm_bridge *bridge,
> >>>>>>> }
> >>>>>>> EXPORT_SYMBOL(drm_atomic_bridge_enable);
> >>>>>>>
> >>>>>>> +/**
> >>>>>>> + * drm_bridge_hpd_enable - enable hot plug detection for the bridge
> >>>>>>> + * @bridge: bridge control structure
> >>>>>>> + * @cb: hot-plug detection callback
> >>>>>>> + * @data: data to be passed to the hot-plug detection callback
> >>>>>>> + *
> >>>>>>> + * Call &drm_bridge_funcs.hpd_enable and register the given @cb and @data as
> >>>>>>> + * hot plug notification callback. From now on the @cb will be called with
> >>>>>>> + * @data when an output status change is detected by the bridge, until hot plug
> >>>>>>> + * notification gets disabled with drm_bridge_hpd_disable().
> >>>>>>> + *
> >>>>>>> + * Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in
> >>>>>>> + * bridge->ops. This function shall not be called when the flag is not set.
> >>>>>>> + *
> >>>>>>> + * Only one hot plug detection callback can be registered at a time, it is an
> >>>>>>> + * error to call this function when hot plug detection is already enabled for
> >>>>>>> + * the bridge.
> >>>>>>> + */
> >>>>>>
> >>>>>> To simplify architecture maybe would be better to enable hpd just on
> >>>>>> bridge attach:
> >>>>>>
> >>>>>> bridge->hpd_cb = cb;
> >>>>>>
> >>>>>> bridge->hpd_data = data;
> >>>>>>
> >>>>>> ret = drm_bridge_attach(...);
> >>>>>
> >>>>> Yeah I like this more. The other problem here is, what if you need more
> >>>>> than 1 callback registers on the same bridge hdp signal?
> >>>>
> >>>> That's why I decided to hide hide HPD through helpers,
> >>>> drm_bridge_hpd_enable() and drm_bridge_hpd_disable() on the listener
> >>>> side, and drm_bridge_hpd_notify() on the event reporter side. While the
> >>>> current implementation is limited to a single listener, only the helpers
> >>>> would need to be changed to extend that to multiple listeners.
> >>>>
> >>>> Note that the .hpd_enable() and .hpd_disable() operations also allow the
> >>>> bridge to disable HPD detection when not used. Doing so keeps the bridge
> >>>> simple, it only needs to care about reporting HPD events when they're
> >>>> enabled, without caring who (if anyone) is listening, and gets clear
> >>>> instructions on whether to enable or disable the HPD hardware (in case
> >>>> it can be disabled).
> >>>>
> >>>>>> This way we could avoid adding new callbacks hpd_(enable|disable)
> >>>>>> without big sacrifices.
> >>>>>>
> >>>>>> One more thing: HPD in DisplayPort/HDMI beside signalling plug/unplug,
> >>>>>> notifies about sink status change, how it translates to this cb?
> >>>>
> >>>> This is something this series doesn't implement. I don't think it would
> >>>> be a big deal, but my knowledge of HPD (especially for DisplayPort) ends
> >>>> here. If you can elaborate on what would be needed, I can implement
> >>>> that.
> >>>>
> >>>>>>> +void drm_bridge_hpd_enable(struct drm_bridge *bridge,
> >>>>>>> + void (*cb)(void *data,
> >>>>>>> + enum drm_connector_status status),
> >>>>>>> + void *data)
> >>>>>>> +{
> >>>>>>> + if (!bridge || !bridge->funcs->hpd_enable)
> >>>>>>> + return;
> >>>>>>> +
> >>>>>>> + mutex_lock(&bridge->hpd_mutex);
> >>>>>>> +
> >>>>>>> + if (WARN(bridge->hpd_cb, "Hot plug detection already enabled\n"))
> >>>>>>> + goto unlock;
> >>>>>>> +
> >>>>>>> + bridge->hpd_cb = cb;
> >>>>>>> + bridge->hpd_data = data;
> >>>>>>> +
> >>>>>>> + bridge->funcs->hpd_enable(bridge);
> >>>>>>> +
> >>>>>>> +unlock:
> >>>>>>> + mutex_unlock(&bridge->hpd_mutex);
> >>>>>>> +}
> >>>>>>> +EXPORT_SYMBOL_GPL(drm_bridge_hpd_enable);
> >>>>>>> +
> >>>>>>> +/**
> >>>>>>> + * drm_bridge_hpd_disable - disable hot plug detection for the bridge
> >>>>>>> + * @bridge: bridge control structure
> >>>>>>> + *
> >>>>>>> + * Call &drm_bridge_funcs.hpd_disable and unregister the hot plug detection
> >>>>>>> + * callback previously registered with drm_bridge_hpd_enable(). Once this
> >>>>>>> + * function returns the callback will not be called by the bridge when an
> >>>>>>> + * output status change occurs.
> >>>>>>> + *
> >>>>>>> + * Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in
> >>>>>>> + * bridge->ops. This function shall not be called when the flag is not set.
> >>>>>>> + */
> >>>>>>> +void drm_bridge_hpd_disable(struct drm_bridge *bridge)
> >>>>>>> +{
> >>>>>>> + if (!bridge || !bridge->funcs->hpd_disable)
> >>>>>>> + return;
> >>>>>>> +
> >>>>>>> + mutex_lock(&bridge->hpd_mutex);
> >>>>>>> + bridge->funcs->hpd_disable(bridge);
> >>>>>>> +
> >>>>>>> + bridge->hpd_cb = NULL;
> >>>>>>> + bridge->hpd_data = NULL;
> >>>>>>> + mutex_unlock(&bridge->hpd_mutex);
> >>>>>>> +}
> >>>>>>> +EXPORT_SYMBOL_GPL(drm_bridge_hpd_disable);
> >>>>>>> +
> >>>>>>> +/**
> >>>>>>> + * drm_bridge_hpd_notify - notify hot plug detection events
> >>>>>>> + * @bridge: bridge control structure
> >>>>>>> + * @status: output connection status
> >>>>>>> + *
> >>>>>>> + * Bridge drivers shall call this function to report hot plug events when they
> >>>>>>> + * detect a change in the output status, when hot plug detection has been
> >>>>>>> + * enabled by the &drm_bridge_funcs.hpd_enable callback.
> >>>>>>> + *
> >>>>>>> + * This function shall be called in a context that can sleep.
> >>>>>>> + */
> >>>>>>> +void drm_bridge_hpd_notify(struct drm_bridge *bridge,
> >>>>>>> + enum drm_connector_status status)
> >>>>>>> +{
> >>>>>>> + mutex_lock(&bridge->hpd_mutex);
> >>>>>>> + if (bridge->hpd_cb)
> >>>>>>> + bridge->hpd_cb(bridge->hpd_data, status);
> >>>>>
> >>>>> So this isn't quite what I had in mind. Instead something like this:
> >>>>>
> >>>>> /* iterates over all bridges in the chain containing @bridge */
> >>>>> for_each_bridge(tmp_bridge, bridge) {
> >>>>> if (tmp_bridge == bridge)
> >>>>> continue;
> >>>>> if (bridge->hpd_notify);
> >>>>> bridge->hpd_notify(tmp_bridge, bridge, status);
> >>>>> }
> >>>>>
> >>>>> encoder = encoder_for_bridge(bridge);
> >>>>> if (encoder->helper_private->bridge_hpd_notify)
> >>>>> encoder->helper_private->bridge_hpd_notify(encoder, bridge, status);
> >>>>>
> >>>>> dev = bridge->dev
> >>>>> if (dev->mode_config.helper_private->bridge_hpd_notify)
> >>>>> dev->mode_config.helper_private->bridge_hpd_notify(dev, bridge, status)
> >>>>>
> >>>>> No register callback needed, no locking needed, everyone gets exactly the
> >>>>> hpd they want/need.
> >>>>
> >>>> I'll reply to this further down the mail thread, to address additional
> >>>> comments.
> >>>>
> >>>>>>> + mutex_unlock(&bridge->hpd_mutex);
> >>>>>>> +}
> >>>>>>> +EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify);
> >>>>>>> +
> >>>>>>> #ifdef CONFIG_OF
> >>>>>>> /**
> >>>>>>> * of_drm_find_bridge - find the bridge corresponding to the device node in
> >>>>>>> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> >>>>>>> index 08dc15f93ded..b9445aa5b1ef 100644
> >>>>>>> --- a/include/drm/drm_bridge.h
> >>>>>>> +++ b/include/drm/drm_bridge.h
> >>>>>>> @@ -23,8 +23,9 @@
> >>>>>>> #ifndef __DRM_BRIDGE_H__
> >>>>>>> #define __DRM_BRIDGE_H__
> >>>>>>>
> >>>>>>> -#include <linux/list.h>
> >>>>>>> #include <linux/ctype.h>
> >>>>>>> +#include <linux/list.h>
> >>>>>>> +#include <linux/mutex.h>
> >>>>>>> #include <drm/drm_mode_object.h>
> >>>>>>> #include <drm/drm_modes.h>
> >>>>>>>
> >>>>>>> @@ -334,6 +335,110 @@ struct drm_bridge_funcs {
> >>>>>>> */
> >>>>>>> void (*atomic_post_disable)(struct drm_bridge *bridge,
> >>>>>>> struct drm_atomic_state *state);
> >>>>>>> +
> >>>>>>> + /**
> >>>>>>> + * @detect:
> >>>>>>> + *
> >>>>>>> + * Check if anything is attached to the bridge output.
> >>>>>>> + *
> >>>>>>> + * This callback is optional, if not implemented the bridge will be
> >>>>>>> + * considered as always having a component attached to its output.
> >>>>>>> + * Bridges that implement this callback shall set the
> >>>>>>> + * DRM_BRIDGE_OP_DETECT flag in their &drm_bridge->ops.
> >>>>>>> + *
> >>>>>>> + * RETURNS:
> >>>>>>> + *
> >>>>>>> + * drm_connector_status indicating the bridge output status.
> >>>>>>> + */
> >>>>>>> + enum drm_connector_status (*detect)(struct drm_bridge *bridge);
> >>>>>>> +
> >>>>>>> + /**
> >>>>>>> + * @get_modes:
> >>>>>>> + *
> >>>>>>> + * Fill all modes currently valid for the sink into the &drm_connector
> >>>>>>> + * with drm_mode_probed_add().
> >>>>>>> + *
> >>>>>>> + * The @get_modes callback is mostly intended to support non-probable
> >>>>>>> + * displays such as many fixed panels. Bridges that support reading
> >>>>>>> + * EDID shall leave @get_modes unimplemented and implement the
> >>>>>>> + * &drm_bridge_funcs->get_edid callback instead.
> >>>>>>> + *
> >>>>>>> + * This callback is optional. Bridges that implement it shall set the
> >>>>>>> + * DRM_BRIDGE_OP_MODES flag in their &drm_bridge->ops.
> >>>>>>> + *
> >>>>>>> + * RETURNS:
> >>>>>>> + *
> >>>>>>> + * The number of modes added by calling drm_mode_probed_add().
> >>>>>>> + */
> >>>>>>> + int (*get_modes)(struct drm_bridge *bridge,
> >>>>>>> + struct drm_connector *connector);
> >>>>>>> +
> >>>>>>> + /**
> >>>>>>> + * @get_edid:
> >>>>>>> + *
> >>>>>>> + * Read and parse the EDID data of the connected display.
> >>>>>>> + *
> >>>>>>> + * The @get_edid callback is the preferred way of reporting mode
> >>>>>>> + * information for a display connected to the bridge output. Bridges
> >>>>>>> + * that support readind EDID shall implement this callback and leave
> >>>>>>> + * the @get_modes callback unimplemented.
> >>>>>>> + *
> >>>>>>> + * The caller of this operation shall first verify the output
> >>>>>>> + * connection status and refrain from reading EDID from a disconnected
> >>>>>>> + * output.
> >>>>>>> + *
> >>>>>>> + * This callback is optional. Bridges that implement it shall set the
> >>>>>>> + * DRM_BRIDGE_OP_EDID flag in their &drm_bridge->ops.
> >>>>>>> + *
> >>>>>>> + * RETURNS:
> >>>>>>> + *
> >>>>>>> + * An edid structure newly allocated with kmalloc() (or similar) on
> >>>>>>> + * success, or NULL otherwise. The caller is responsible for freeing
> >>>>>>> + * the returned edid structure with kfree().
> >>>>>>> + */
> >>>>>>> + struct edid *(*get_edid)(struct drm_bridge *bridge,
> >>>>>>> + struct drm_connector *connector);
> >>>>>>
> >>>>>> It overlaps with get_modes, I guess presence of one ops should disallow
> >>>>>> presence of another one?
> >>>>>>
> >>>>>> I am not really convinced we need this op at all, cannot we just assign
> >>>>>> some helper function to .get_modes cb, which will do the same?
> >>>>>
> >>>>> Plan B): ditch ->get_edid, require that the driver has ->get_modes in that
> >>>>> case, and require that if it has an edid it must fill out connector->info
> >>>>> and connector->edid correctly.
> >>>>
> >>>> I think that's doable, I'll have a look.
> >>>
> >>> So I had a look, and while this is doable, it would essentially mean
> >>> that all bridges that retrieve modes from EDID would have to roll out
> >>> their own version of the following code:
> >>>
> >>> static int drm_bridge_connector_get_modes_edid(struct drm_connector *connector,
> >>> struct drm_bridge *bridge)
> >>> {
> >>> enum drm_connector_status status;
> >>> struct edid *edid;
> >>> int n;
> >>>
> >>> status = drm_bridge_connector_detect(connector, false);
> >>> if (status != connector_status_connected)
> >>> goto no_edid;
> >>>
> >>> edid = bridge->funcs->get_edid(bridge, connector);
> >>> if (!edid || !drm_edid_is_valid(edid)) {
> >>> kfree(edid);
> >>> goto no_edid;
> >>> }
> >>>
> >>> drm_connector_update_edid_property(connector, edid);
> >>> n = drm_add_edid_modes(connector, edid);
> >>>
> >>> kfree(edid);
> >>> return n;
> >>>
> >>> no_edid:
> >>> drm_connector_update_edid_property(connector, NULL);
> >>> return 0;
> >>> }
> >>>
> >>> Is this desired ?
> >>
> >> We store the edid, and we store a lot of decoded information in
> >> drm_connector->display_info. Can't they just look there? Re-fetching the
> >> edid definitely sounds like the wrong thing to do.
> >>
> >> We might run into some ordering issue here I guess with hotplugs and who's
> >> fetching the edid and everything like that.
> >
> > That's exactly what I was about to answer after reading your first
> > paragraph :-) I believe caching EDID is a good idea, but my familiarity
> > with hotplug-related issues is limited to a handful of systems, and I'm
> > sure I'm missing some common problems. If you can tell me how you think
> > this should be done, I can give it a try.
>
> I think all you need to do is make sure that when handling a hpd, the edid
> is fetched first. Before other parts of the bridge try to reconfigure
> themselves ...
>
> >> Also maybe I'm missing the point here, and thinking too much of
> >> ->get_modes on the connector. But then I'm not clear on why the bridge
> >> needs the connector, and why it instead can't just return the edid it can
> >> read and let the caller/core figure out everything else?
> >
> > That's exactly what the .get_edid() operation that you asked me to
> > remove did... :-) You didn't like the fact that it duplicated the
> > .get_modes() logic. Should I add it back, and clearly document
> > .get_modes() as a fallback used only when the connector doesn't use EDID
> > ?
>
> I guess I'm making a bit a fool of myself here. What I meant is that if we
> do want to keep ->get_edid, then why do you need to pass the connector?
> Just return the edid blob, and let the caller parse it, and stuff all
> relevant data into drm_connector. Just thinking along the lines of your
> goal of making the bridge drivers as dumb as possible.
>
> Same thing for ->get_modes would be neat too, but we don't have a nice
> datastructure for this. We'd need to pass both a list_head and a pointer
> to the drm_display_info I think.
>
> That would decouple bridges even more from connector, which I think is
> somewhere on your goal list ...
So I had a look at that. We would need to remove the connector argument
from drm_do_get_edid(). The connector currently stores a few fields
related to EDID parsing:
/**
* @null_edid_counter: track sinks that give us all zeros for the EDID.
* Needed to workaround some HW bugs where we get all 0s
*/
int null_edid_counter;
/** @bad_edid_counter: track sinks that give us an EDID with invalid checksum */
unsigned bad_edid_counter;
/**
* @edid_corrupt: Indicates whether the last read EDID was corrupt. Used
* in Displayport compliance testing - Displayport Link CTS Core 1.2
* rev1.1 4.2.2.6
*/
bool edid_corrupt;
We would need to decouple that from drm_connector. One option would be
to create a new drm_edid structure that would store those three fields,
as well as a struct edid, and return it from drm_do_get_edid() instead
of the raw struct edid. Would you prefer a different solution ? Do you
think that's a prerequisite to for this patch ?
> >>>>> Btw if a hpd happens, who's responible for making sure the edid/mode list
> >>>>> in the connector is up-to-date? With your current callback design that's
> >>>>> up to the callback, which doesn't feel great. Maybe drm_bridge_hpd_notify
> >>>>> should guarantee that it'll first walk the connectors to update status and
> >>>>> edid/mode list for the final drm_connector. And then instead of just
> >>>>> passing the simple "status", it'll pass the connector, with everything
> >>>>> correctly updated.
> >>>>>
> >>>>> Otherwise everyone interested in that hpd signal will go and re-fetch the
> >>>>> edid, which is not so awesome :-)
> >>>>
> >>>> With the current design there's a single listener, so it's not a big
> >>>> deal :-) Furthermore, the listener is the helper that creates a
> >>>> connector on top of a chain of bridges, so it's a pretty good place to
> >>>> handle this. See the call to drm_kms_helper_hotplug_event() in
> >>>> drm_bridge_connector_hpd_cb().
> >>>>
> >>>> I'm all for reworking HPD and mode fetching, but I think it's a bit too
> >>>> big of a requirement as a prerequisite for this series (or as part of
> >>>> this series). We have hardware that can report HPD with various level of
> >>>> details (from "something happened on a connector" to "this particular
> >>>> event happened on this particular connector"), and we channel that
> >>>> through helpers such as drm_kms_helper_hotplug_event() that lose the
> >>>> details and go through a heavy mechanism to refetch everything. I
> >>>> understand this is needed in many cases, but I think there's room for
> >>>> improvement. This series, in my opinion, doesn't go in the wrong
> >>>> direction in that regard, as it eventually calls
> >>>> drm_kms_helper_hotplug_event(), so I think improvements would make sense
> >>>> on top of it. I'm even willing to work on this, provided I get feedback
> >>>> on what is desired.
> >>>>
> >>>>>>> + /**
> >>>>>>> + * @lost_hotplug:
> >>>>>>> + *
> >>>>>>> + * Notify the bridge of display disconnection.
> >>>>>>> + *
> >>>>>>> + * This callback is optional, it may be implemented by bridges that
> >>>>>>> + * need to be notified of display disconnection for internal reasons.
> >>>>>>> + * One use case is to reset the internal state of CEC controllers for
> >>>>>>> + * HDMI bridges.
> >>>>>>> + */
> >>>>>>> + void (*lost_hotplug)(struct drm_bridge *bridge);
> >>>>>>> +
> >>>>>>> + /**
> >>>>>>> + * @hpd_enable:
> >>>>>>> + *
> >>>>>>> + * Enable hot plug detection. From now on the bridge shall call
> >>>>>>> + * drm_bridge_hpd_notify() each time a change is detected in the output
> >>>>>>> + * connection status, until hot plug detection gets disabled with
> >>>>>>> + * @hpd_disable.
> >>>>>>> + *
> >>>>>>> + * This callback is optional and shall only be implemented by bridges
> >>>>>>> + * that support hot-plug notification without polling. Bridges that
> >>>>>>> + * implement it shall also implement the @hpd_disable callback and set
> >>>>>>> + * the DRM_BRIDGE_OP_HPD flag in their &drm_bridge->ops.
> >>>>>>> + */
> >>>>>>> + void (*hpd_enable)(struct drm_bridge *bridge);
> >>>>>>> +
> >>>>>>> + /**
> >>>>>>> + * @hpd_disable:
> >>>>>>> + *
> >>>>>>> + * Disable hot plug detection. Once this function returns the bridge
> >>>>>>> + * shall not call drm_bridge_hpd_notify() when a change in the output
> >>>>>>> + * connection status occurs.
> >>>>>>> + *
> >>>>>>> + * This callback is optional and shall only be implemented by bridges
> >>>>>>> + * that support hot-plug notification without polling. Bridges that
> >>>>>>> + * implement it shall also implement the @hpd_enable callback and set
> >>>>>>> + * the DRM_BRIDGE_OP_HPD flag in their &drm_bridge->ops.
> >>>>>>> + */
> >>>>>>> + void (*hpd_disable)(struct drm_bridge *bridge);
> >>>>>>> };
> >>>>>>>
> >>>>>>> /**
> >>>>>>> @@ -372,6 +477,38 @@ struct drm_bridge_timings {
> >>>>>>> bool dual_link;
> >>>>>>> };
> >>>>>>>
> >>>>>>> +/**
> >>>>>>> + * enum drm_bridge_ops - Bitmask of operations supported by the bridge
> >>>>>>> + */
> >>>>>>> +enum drm_bridge_ops {
> >>>>>>> + /**
> >>>>>>> + * @DRM_BRIDGE_OP_DETECT: The bridge can detect displays connected to
> >>>>>>> + * its output. Bridges that set this flag shall implement the
> >>>>>>> + * &drm_bridge_funcs->detect callback.
> >>>>>>> + */
> >>>>>>> + DRM_BRIDGE_OP_DETECT = BIT(0),
> >>>>>>> + /**
> >>>>>>> + * @DRM_BRIDGE_OP_EDID: The bridge can retrieve the EDID of the display
> >>>>>>> + * connected to its output. Bridges that set this flag shall implement
> >>>>>>> + * the &drm_bridge_funcs->get_edid callback.
> >>>>>>> + */
> >>>>>>> + DRM_BRIDGE_OP_EDID = BIT(1),
> >>>>>>> + /**
> >>>>>>> + * @DRM_BRIDGE_OP_HPD: The bridge can detect hot-plug and hot-unplug
> >>>>>>> + * without requiring polling. Bridges that set this flag shall
> >>>>>>> + * implement the &drm_bridge_funcs->hpd_enable and
> >>>>>>> + * &drm_bridge_funcs->disable_hpd_cb callbacks.
> >>>>>>> + */
> >>>>>>> + DRM_BRIDGE_OP_HPD = BIT(2),
> >>>>>>> + /**
> >>>>>>> + * @DRM_BRIDGE_OP_MODES: The bridge can retrieving the modes supported
> >>>>>>> + * by the display at its output. This does not include readind EDID
> >>>>>>> + * which is separately covered by @DRM_BRIDGE_OP_EDID. Bridges that set
> >>>>>>> + * this flag shall implement the &drm_bridge_funcs->get_modes callback.
> >>>>>>> + */
> >>>>>>> + DRM_BRIDGE_OP_MODES = BIT(3),
> >>>>>>> +};
> >>>>>>> +
> >>>>>>> /**
> >>>>>>> * struct drm_bridge - central DRM bridge control structure
> >>>>>>> */
> >>>>>>> @@ -398,6 +535,29 @@ struct drm_bridge {
> >>>>>>> const struct drm_bridge_funcs *funcs;
> >>>>>>> /** @driver_private: pointer to the bridge driver's internal context */
> >>>>>>> void *driver_private;
> >>>>>>> + /** @ops: bitmask of operations supported by the bridge */
> >>>>>>> + enum drm_bridge_ops ops;
> >>>>>>> + /**
> >>>>>>> + * @type: Type of the connection at the bridge output
> >>>>>>> + * (DRM_MODE_CONNECTOR_*). For bridges at the end of this chain this
> >>>>>>> + * identifies the type of connected display.
> >>>>>>> + */
> >>>>>>> + int type;
> >>>>>>> + /** private: */
> >>>>>>> + /**
> >>>>>>> + * @hpd_mutex: Protects the @hpd_cb and @hpd_data fields.
> >>>>>>> + */
> >>>>>>> + struct mutex hpd_mutex;
> >>>>>>> + /**
> >>>>>>> + * @hpd_cb: Hot plug detection callback, registered with
> >>>>>>> + * drm_bridge_hpd_enable().
> >>>>>>> + */
> >>>>>>> + void (*hpd_cb)(void *data, enum drm_connector_status status);
> >>>>>>> + /**
> >>>>>>> + * @hpd_data: Private data passed to the Hot plug detection callback
> >>>>>>> + * @hpd_cb.
> >>>>>>> + */
> >>>>>>> + void *hpd_data;
> >>>>>>> };
> >>>>>>>
> >>>>>>> void drm_bridge_add(struct drm_bridge *bridge);
> >>>>>>> @@ -428,6 +588,14 @@ void drm_atomic_bridge_pre_enable(struct drm_bridge *bridge,
> >>>>>>> void drm_atomic_bridge_enable(struct drm_bridge *bridge,
> >>>>>>> struct drm_atomic_state *state);
> >>>>>>>
> >>>>>>> +void drm_bridge_hpd_enable(struct drm_bridge *bridge,
> >>>>>>> + void (*cb)(void *data,
> >>>>>>> + enum drm_connector_status status),
> >>>>>>> + void *data);
> >>>>>>> +void drm_bridge_hpd_disable(struct drm_bridge *bridge);
> >>>>>>> +void drm_bridge_hpd_notify(struct drm_bridge *bridge,
> >>>>>>> + enum drm_connector_status status);
> >>>>>>> +
> >>>>>>> #ifdef CONFIG_DRM_PANEL_BRIDGE
> >>>>>>> struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel,
> >>>>>>> u32 connector_type);
--
Regards,
Laurent Pinchart
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