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
- Bridge output type
- I2C adapter for DDC access
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.
Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
Reviewed-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
Tested-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
Reviewed-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
---
Changes since v6:
- Don't check for NULL bridge in drm_bridge_hpd_enable() and
drm_bridge_hpd_disable()
Changes since v3:
- Fix typos
Changes since v2:
- Add wrappers around the .detect(), .get_modes() and .get_edid()
operations
- Warn bridge drivers about valid usage of the connector argument to
.get_modes() and .get_edid()
Changes since v1:
- Make .hpd_enable() and .hpd_disable() optional
- Rename .lost_hotplug() to .hpd_notify()
- Add ddc field to drm_bridge
---
drivers/gpu/drm/drm_bridge.c | 201 ++++++++++++++++++++++++++++++++++-
include/drm/drm_bridge.h | 192 ++++++++++++++++++++++++++++++++-
2 files changed, 391 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 5f55a9e17a7c..d236984a963e 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -82,6 +82,8 @@ 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);
@@ -98,6 +100,8 @@ 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);
@@ -228,7 +232,7 @@ void drm_bridge_detach(struct drm_bridge *bridge)
* Bridge drivers expose operations through the &drm_bridge_funcs structure.
* The DRM internals (atomic and CRTC helpers) use the helpers defined in
* drm_bridge.c to call bridge operations. Those operations are divided in
- * two big categories to support different parts of the bridge usage.
+ * three big categories to support different parts of the bridge usage.
*
* - The encoder-related operations support control of the bridges in the
* chain, and are roughly counterparts to the &drm_encoder_helper_funcs
@@ -258,6 +262,43 @@ void drm_bridge_detach(struct drm_bridge *bridge)
* implement them shall thus also implement the atomic version of the
* encoder-related operations. This feature is not supported by the legacy
* CRTC helpers.
+ *
+ * - The connector-related operations support implementing a &drm_connector
+ * based on a chain of bridges. DRM bridges traditionally create a
+ * &drm_connector for bridges meant to be used at the end of the chain. This
+ * puts additional burden on bridge drivers, especially for bridges that may
+ * be used in the middle of a chain or at the end of it. Furthermore, it
+ * requires all operations of the &drm_connector to be handled by a single
+ * bridge, which doesn't always match the hardware architecture.
+ *
+ * To simplify bridge drivers and make the connector implementation more
+ * flexible, a new model allows bridges to unconditionally skip creation of
+ * &drm_connector and instead expose &drm_bridge_funcs operations to support
+ * an externally-implemented &drm_connector. Those operations are
+ * &drm_bridge_funcs.detect, &drm_bridge_funcs.get_modes,
+ * &drm_bridge_funcs.get_edid, &drm_bridge_funcs.hpd_notify,
+ * &drm_bridge_funcs.hpd_enable and &drm_bridge_funcs.hpd_disable. When
+ * implemented, display drivers shall create a &drm_connector instance for
+ * each chain of bridges, and implement those connector instances based on
+ * the bridge connector operations.
+ *
+ * Bridge drivers shall implement the connector-related operations for all
+ * the features that the bridge hardware support. For instance, if a bridge
+ * supports reading EDID, the &drm_bridge_funcs.get_edid shall be
+ * implemented. This however doesn't mean that the DDC lines are wired to the
+ * bridge on a particular platform, as they could also be connected to an I2C
+ * controller of the SoC. Support for the connector-related operations on the
+ * running platform is reported through the &drm_bridge.ops flags. Bridge
+ * drivers shall detect which operations they can support on the platform
+ * (usually this information is provided by ACPI or DT), and set the
+ * &drm_bridge.ops flags for all supported operations. A flag shall only be
+ * set if the corresponding &drm_bridge_funcs operation is implemented, but
+ * an implemented operation doesn't necessarily imply that the corresponding
+ * flag will be set. Display drivers shall use the &drm_bridge.ops flags to
+ * decide which bridge to delegate a connector operation to. This mechanism
+ * allows providing a single static const &drm_bridge_funcs instance in
+ * bridge drivers, improving security by storing function pointers in
+ * read-only memory.
*/
/**
@@ -957,6 +998,164 @@ int drm_atomic_bridge_chain_check(struct drm_bridge *bridge,
}
EXPORT_SYMBOL(drm_atomic_bridge_chain_check);
+/**
+ * drm_bridge_detect - check if anything is attached to the bridge output
+ * @bridge: bridge control structure
+ *
+ * If the bridge supports output detection, as reported by the
+ * DRM_BRIDGE_OP_DETECT bridge ops flag, call &drm_bridge_funcs.detect for the
+ * bridge and return the connection status. Otherwise return
+ * connector_status_unknown.
+ *
+ * RETURNS:
+ * The detection status on success, or connector_status_unknown if the bridge
+ * doesn't support output detection.
+ */
+enum drm_connector_status drm_bridge_detect(struct drm_bridge *bridge)
+{
+ if (!(bridge->ops & DRM_BRIDGE_OP_DETECT))
+ return connector_status_unknown;
+
+ return bridge->funcs->detect(bridge);
+}
+EXPORT_SYMBOL_GPL(drm_bridge_detect);
+
+/**
+ * drm_bridge_get_modes - fill all modes currently valid for the sink into the
+ * @connector
+ * @bridge: bridge control structure
+ * @connector: the connector to fill with modes
+ *
+ * If the bridge supports output modes retrieval, as reported by the
+ * DRM_BRIDGE_OP_MODES bridge ops flag, call &drm_bridge_funcs.get_modes to
+ * fill the connector with all valid modes and return the number of modes
+ * added. Otherwise return 0.
+ *
+ * RETURNS:
+ * The number of modes added to the connector.
+ */
+int drm_bridge_get_modes(struct drm_bridge *bridge,
+ struct drm_connector *connector)
+{
+ if (!(bridge->ops & DRM_BRIDGE_OP_MODES))
+ return 0;
+
+ return bridge->funcs->get_modes(bridge, connector);
+}
+EXPORT_SYMBOL_GPL(drm_bridge_get_modes);
+
+/**
+ * drm_bridge_get_edid - get the EDID data of the connected display
+ * @bridge: bridge control structure
+ * @connector: the connector to read EDID for
+ *
+ * If the bridge supports output EDID retrieval, as reported by the
+ * DRM_BRIDGE_OP_EDID bridge ops flag, call &drm_bridge_funcs.get_edid to
+ * get the EDID and return it. Otherwise return ERR_PTR(-ENOTSUPP).
+ *
+ * RETURNS:
+ * The retrieved EDID on success, or an error pointer otherwise.
+ */
+struct edid *drm_bridge_get_edid(struct drm_bridge *bridge,
+ struct drm_connector *connector)
+{
+ if (!(bridge->ops & DRM_BRIDGE_OP_EDID))
+ return ERR_PTR(-ENOTSUPP);
+
+ return bridge->funcs->get_edid(bridge, connector);
+}
+EXPORT_SYMBOL_GPL(drm_bridge_get_edid);
+
+/**
+ * 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 if implemented 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.
+ */
+void drm_bridge_hpd_enable(struct drm_bridge *bridge,
+ void (*cb)(void *data,
+ enum drm_connector_status status),
+ void *data)
+{
+ if (!(bridge->ops & DRM_BRIDGE_OP_HPD))
+ 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;
+
+ if (bridge->funcs->hpd_enable)
+ 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 if implemented 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->ops & DRM_BRIDGE_OP_HPD))
+ return;
+
+ mutex_lock(&bridge->hpd_mutex);
+ if (bridge->funcs->hpd_disable)
+ 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 drm_bridge_hpd_enable().
+ *
+ * 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);
+ 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 38de129d5947..9d5d750973e9 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_atomic.h>
#include <drm/drm_encoder.h>
@@ -33,7 +34,10 @@
struct drm_bridge;
struct drm_bridge_timings;
+struct drm_connector;
struct drm_panel;
+struct edid;
+struct i2c_adapter;
/**
* struct drm_bridge_funcs - drm_bridge control functions
@@ -497,6 +501,119 @@ struct drm_bridge_funcs {
* giving the reason of the failure otherwise.
*/
struct drm_bridge_state *(*atomic_reset)(struct drm_bridge *bridge);
+
+ /**
+ * @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-probeable
+ * 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.
+ *
+ * The connector parameter shall be used for the sole purpose of
+ * filling modes, and shall not be stored internally by bridge drivers
+ * for future usage.
+ *
+ * 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 reading 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.
+ *
+ * The connector parameter shall be used for the sole purpose of EDID
+ * retrieval and parsing, and shall not be stored internally by bridge
+ * drivers for future usage.
+ *
+ * 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);
+
+ /**
+ * @hpd_notify:
+ *
+ * Notify the bridge of hot plug detection.
+ *
+ * This callback is optional, it may be implemented by bridges that
+ * need to be notified of display connection or disconnection for
+ * internal reasons. One use case is to reset the internal state of CEC
+ * controllers for HDMI bridges.
+ */
+ void (*hpd_notify)(struct drm_bridge *bridge,
+ enum drm_connector_status status);
+
+ /**
+ * @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);
};
/**
@@ -535,6 +652,39 @@ 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->hpd_disable callbacks if they support enabling
+ * and disabling hot-plug detection dynamically.
+ */
+ DRM_BRIDGE_OP_HPD = BIT(2),
+ /**
+ * @DRM_BRIDGE_OP_MODES: The bridge can retrieve the modes supported
+ * by the display at its output. This does not include reading 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
*/
@@ -563,6 +713,33 @@ 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;
+ /**
+ * @ddc: Associated I2C adapter for DDC access, if any.
+ */
+ struct i2c_adapter *ddc;
+ /** 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;
};
static inline struct drm_bridge *
@@ -669,6 +846,19 @@ drm_atomic_helper_bridge_propagate_bus_fmt(struct drm_bridge *bridge,
u32 output_fmt,
unsigned int *num_input_fmts);
+enum drm_connector_status drm_bridge_detect(struct drm_bridge *bridge);
+int drm_bridge_get_modes(struct drm_bridge *bridge,
+ struct drm_connector *connector);
+struct edid *drm_bridge_get_edid(struct drm_bridge *bridge,
+ struct drm_connector *connector);
+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);
struct drm_bridge *drm_panel_bridge_add_typed(struct drm_panel *panel,
--
Regards,
Laurent Pinchart
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