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authorMaarten Lankhorst <maarten.lankhorst@linux.intel.com>2017-04-06 20:55:20 +0200
committerMaarten Lankhorst <maarten.lankhorst@linux.intel.com>2017-04-06 21:29:23 +0200
commit6c5ed5ae353cdf156f9ac4db17e15db56b4de880 (patch)
treed24402c7bef516de0f3ec69318606b67065954cb
parentdrm: virtio: fix virtio_gpu_cursor_formats (diff)
downloadlinux-dev-6c5ed5ae353cdf156f9ac4db17e15db56b4de880.tar.xz
linux-dev-6c5ed5ae353cdf156f9ac4db17e15db56b4de880.zip
drm/atomic: Acquire connection_mutex lock in drm_helper_probe_single_connector_modes, v4.
mode_valid() called from drm_helper_probe_single_connector_modes() may need to look at connector->state because what a valid mode is may depend on connector properties being set. For example some HDMI modes might be rejected when a connector property forces the connector into DVI mode. Some implementations of detect() already lock all state, so we have to pass an acquire_ctx to them to prevent a deadlock. This means changing the function signature of detect() slightly, and passing the acquire_ctx for locking multiple crtc's. For the callbacks, it will always be non-zero. To allow callers not to worry about this, drm_helper_probe_detect_ctx is added which might handle -EDEADLK for you. Changes since v1: - Always set ctx parameter. Changes since v2: - Always take connection_mutex when probing. Changes since v3: - Remove the ctx from intel_dp_long_pulse, and add WARN_ON(!connection_mutex) (danvet) - Update docs to clarify the locking situation. (danvet) Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Boris Brezillon <boris.brezillon@free-electrons.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/1491504920-4017-1-git-send-email-maarten.lankhorst@linux.intel.com
-rw-r--r--drivers/gpu/drm/drm_probe_helper.c100
-rw-r--r--drivers/gpu/drm/i915/intel_crt.c25
-rw-r--r--drivers/gpu/drm/i915/intel_display.c25
-rw-r--r--drivers/gpu/drm/i915/intel_dp.c21
-rw-r--r--drivers/gpu/drm/i915/intel_drv.h8
-rw-r--r--drivers/gpu/drm/i915/intel_hotplug.c3
-rw-r--r--drivers/gpu/drm/i915/intel_tv.c21
-rw-r--r--include/drm/drm_connector.h6
-rw-r--r--include/drm/drm_crtc_helper.h3
-rw-r--r--include/drm/drm_modeset_helper_vtables.h36
10 files changed, 187 insertions, 61 deletions
diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index efb5e5e8ce62..1b0c14ab3fff 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -169,12 +169,73 @@ void drm_kms_helper_poll_enable(struct drm_device *dev)
EXPORT_SYMBOL(drm_kms_helper_poll_enable);
static enum drm_connector_status
-drm_connector_detect(struct drm_connector *connector, bool force)
+drm_helper_probe_detect_ctx(struct drm_connector *connector, bool force)
{
- return connector->funcs->detect ?
- connector->funcs->detect(connector, force) :
- connector_status_connected;
+ const struct drm_connector_helper_funcs *funcs = connector->helper_private;
+ struct drm_modeset_acquire_ctx ctx;
+ int ret;
+
+ drm_modeset_acquire_init(&ctx, 0);
+
+retry:
+ ret = drm_modeset_lock(&connector->dev->mode_config.connection_mutex, &ctx);
+ if (!ret) {
+ if (funcs->detect_ctx)
+ ret = funcs->detect_ctx(connector, &ctx, force);
+ else if (connector->funcs->detect)
+ ret = connector->funcs->detect(connector, force);
+ else
+ ret = connector_status_connected;
+ }
+
+ if (ret == -EDEADLK) {
+ drm_modeset_backoff(&ctx);
+ goto retry;
+ }
+
+ if (WARN_ON(ret < 0))
+ ret = connector_status_unknown;
+
+ drm_modeset_drop_locks(&ctx);
+ drm_modeset_acquire_fini(&ctx);
+
+ return ret;
+}
+
+/**
+ * drm_helper_probe_detect - probe connector status
+ * @connector: connector to probe
+ * @ctx: acquire_ctx, or NULL to let this function handle locking.
+ * @force: Whether destructive probe operations should be performed.
+ *
+ * This function calls the detect callbacks of the connector.
+ * This function returns &drm_connector_status, or
+ * if @ctx is set, it might also return -EDEADLK.
+ */
+int
+drm_helper_probe_detect(struct drm_connector *connector,
+ struct drm_modeset_acquire_ctx *ctx,
+ bool force)
+{
+ const struct drm_connector_helper_funcs *funcs = connector->helper_private;
+ struct drm_device *dev = connector->dev;
+ int ret;
+
+ if (!ctx)
+ return drm_helper_probe_detect_ctx(connector, force);
+
+ ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
+ if (ret)
+ return ret;
+
+ if (funcs->detect_ctx)
+ return funcs->detect_ctx(connector, ctx, force);
+ else if (connector->funcs->detect)
+ return connector->funcs->detect(connector, force);
+ else
+ return connector_status_connected;
}
+EXPORT_SYMBOL(drm_helper_probe_detect);
/**
* drm_helper_probe_single_connector_modes - get complete set of display modes
@@ -239,15 +300,27 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
struct drm_display_mode *mode;
const struct drm_connector_helper_funcs *connector_funcs =
connector->helper_private;
- int count = 0;
+ int count = 0, ret;
int mode_flags = 0;
bool verbose_prune = true;
enum drm_connector_status old_status;
+ struct drm_modeset_acquire_ctx ctx;
WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
+ drm_modeset_acquire_init(&ctx, 0);
+
DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
connector->name);
+
+retry:
+ ret = drm_modeset_lock(&dev->mode_config.connection_mutex, &ctx);
+ if (ret == -EDEADLK) {
+ drm_modeset_backoff(&ctx);
+ goto retry;
+ } else
+ WARN_ON(ret < 0);
+
/* set all old modes to the stale state */
list_for_each_entry(mode, &connector->modes, head)
mode->status = MODE_STALE;
@@ -263,7 +336,15 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
if (connector->funcs->force)
connector->funcs->force(connector);
} else {
- connector->status = drm_connector_detect(connector, true);
+ ret = drm_helper_probe_detect(connector, &ctx, true);
+
+ if (ret == -EDEADLK) {
+ drm_modeset_backoff(&ctx);
+ goto retry;
+ } else if (WARN(ret < 0, "Invalid return value %i for connector detection\n", ret))
+ ret = connector_status_unknown;
+
+ connector->status = ret;
}
/*
@@ -355,6 +436,9 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
prune:
drm_mode_prune_invalid(dev, &connector->modes, verbose_prune);
+ drm_modeset_drop_locks(&ctx);
+ drm_modeset_acquire_fini(&ctx);
+
if (list_empty(&connector->modes))
return 0;
@@ -440,7 +524,7 @@ static void output_poll_execute(struct work_struct *work)
repoll = true;
- connector->status = drm_connector_detect(connector, false);
+ connector->status = drm_helper_probe_detect(connector, NULL, false);
if (old_status != connector->status) {
const char *old, *new;
@@ -588,7 +672,7 @@ bool drm_helper_hpd_irq_event(struct drm_device *dev)
old_status = connector->status;
- connector->status = drm_connector_detect(connector, false);
+ connector->status = drm_helper_probe_detect(connector, NULL, false);
DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
connector->base.id,
connector->name,
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index 8c82607294c6..2797bf37c3ac 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -669,15 +669,16 @@ static const struct dmi_system_id intel_spurious_crt_detect[] = {
{ }
};
-static enum drm_connector_status
-intel_crt_detect(struct drm_connector *connector, bool force)
+static int
+intel_crt_detect(struct drm_connector *connector,
+ struct drm_modeset_acquire_ctx *ctx,
+ bool force)
{
struct drm_i915_private *dev_priv = to_i915(connector->dev);
struct intel_crt *crt = intel_attached_crt(connector);
struct intel_encoder *intel_encoder = &crt->base;
- enum drm_connector_status status;
+ int status, ret;
struct intel_load_detect_pipe tmp;
- struct drm_modeset_acquire_ctx ctx;
DRM_DEBUG_KMS("[CONNECTOR:%d:%s] force=%d\n",
connector->base.id, connector->name,
@@ -721,10 +722,9 @@ intel_crt_detect(struct drm_connector *connector, bool force)
goto out;
}
- drm_modeset_acquire_init(&ctx, 0);
-
/* for pre-945g platforms use load detect */
- if (intel_get_load_detect_pipe(connector, NULL, &tmp, &ctx)) {
+ ret = intel_get_load_detect_pipe(connector, NULL, &tmp, ctx);
+ if (ret > 0) {
if (intel_crt_detect_ddc(connector))
status = connector_status_connected;
else if (INTEL_GEN(dev_priv) < 4)
@@ -734,12 +734,11 @@ intel_crt_detect(struct drm_connector *connector, bool force)
status = connector_status_disconnected;
else
status = connector_status_unknown;
- intel_release_load_detect_pipe(connector, &tmp, &ctx);
- } else
+ intel_release_load_detect_pipe(connector, &tmp, ctx);
+ } else if (ret == 0)
status = connector_status_unknown;
-
- drm_modeset_drop_locks(&ctx);
- drm_modeset_acquire_fini(&ctx);
+ else if (ret < 0)
+ status = ret;
out:
intel_display_power_put(dev_priv, intel_encoder->power_domain);
@@ -811,7 +810,6 @@ void intel_crt_reset(struct drm_encoder *encoder)
static const struct drm_connector_funcs intel_crt_connector_funcs = {
.dpms = drm_atomic_helper_connector_dpms,
- .detect = intel_crt_detect,
.fill_modes = drm_helper_probe_single_connector_modes,
.late_register = intel_connector_register,
.early_unregister = intel_connector_unregister,
@@ -823,6 +821,7 @@ static const struct drm_connector_funcs intel_crt_connector_funcs = {
};
static const struct drm_connector_helper_funcs intel_crt_connector_helper_funcs = {
+ .detect_ctx = intel_crt_detect,
.mode_valid = intel_crt_mode_valid,
.get_modes = intel_crt_get_modes,
};
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 602fd479dd30..e217d04133e6 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -9480,10 +9480,10 @@ static int intel_modeset_setup_plane_state(struct drm_atomic_state *state,
return 0;
}
-bool intel_get_load_detect_pipe(struct drm_connector *connector,
- struct drm_display_mode *mode,
- struct intel_load_detect_pipe *old,
- struct drm_modeset_acquire_ctx *ctx)
+int intel_get_load_detect_pipe(struct drm_connector *connector,
+ struct drm_display_mode *mode,
+ struct intel_load_detect_pipe *old,
+ struct drm_modeset_acquire_ctx *ctx)
{
struct intel_crtc *intel_crtc;
struct intel_encoder *intel_encoder =
@@ -9506,10 +9506,7 @@ bool intel_get_load_detect_pipe(struct drm_connector *connector,
old->restore_state = NULL;
-retry:
- ret = drm_modeset_lock(&config->connection_mutex, ctx);
- if (ret)
- goto fail;
+ WARN_ON(!drm_modeset_is_locked(&config->connection_mutex));
/*
* Algorithm gets a little messy:
@@ -9659,10 +9656,8 @@ fail:
restore_state = NULL;
}
- if (ret == -EDEADLK) {
- drm_modeset_backoff(ctx);
- goto retry;
- }
+ if (ret == -EDEADLK)
+ return ret;
return false;
}
@@ -15030,6 +15025,7 @@ static void intel_enable_pipe_a(struct drm_device *dev)
struct drm_connector *crt = NULL;
struct intel_load_detect_pipe load_detect_temp;
struct drm_modeset_acquire_ctx *ctx = dev->mode_config.acquire_ctx;
+ int ret;
/* We can't just switch on the pipe A, we need to set things up with a
* proper mode and output configuration. As a gross hack, enable pipe A
@@ -15046,7 +15042,10 @@ static void intel_enable_pipe_a(struct drm_device *dev)
if (!crt)
return;
- if (intel_get_load_detect_pipe(crt, NULL, &load_detect_temp, ctx))
+ ret = intel_get_load_detect_pipe(crt, NULL, &load_detect_temp, ctx);
+ WARN(ret < 0, "All modeset mutexes are locked, but intel_get_load_detect_pipe failed\n");
+
+ if (ret > 0)
intel_release_load_detect_pipe(crt, &load_detect_temp, ctx);
}
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index fd96a6cf7326..6e04cb54e3ff 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4566,7 +4566,7 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
intel_dp->has_audio = false;
}
-static enum drm_connector_status
+static int
intel_dp_long_pulse(struct intel_connector *intel_connector)
{
struct drm_connector *connector = &intel_connector->base;
@@ -4577,6 +4577,8 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
enum drm_connector_status status;
u8 sink_irq_vector = 0;
+ WARN_ON(!drm_modeset_is_locked(&connector->dev->mode_config.connection_mutex));
+
intel_display_power_get(to_i915(dev), intel_dp->aux_power_domain);
/* Can't disconnect eDP, but you can close the lid... */
@@ -4635,14 +4637,7 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
status = connector_status_disconnected;
goto out;
} else if (connector->status == connector_status_connected) {
- /*
- * If display was connected already and is still connected
- * check links status, there has been known issues of
- * link loss triggerring long pulse!!!!
- */
- drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
intel_dp_check_link_status(intel_dp);
- drm_modeset_unlock(&dev->mode_config.connection_mutex);
goto out;
}
@@ -4682,11 +4677,13 @@ out:
return status;
}
-static enum drm_connector_status
-intel_dp_detect(struct drm_connector *connector, bool force)
+static int
+intel_dp_detect(struct drm_connector *connector,
+ struct drm_modeset_acquire_ctx *ctx,
+ bool force)
{
struct intel_dp *intel_dp = intel_attached_dp(connector);
- enum drm_connector_status status = connector->status;
+ int status = connector->status;
DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
connector->base.id, connector->name);
@@ -5014,7 +5011,6 @@ void intel_dp_encoder_reset(struct drm_encoder *encoder)
static const struct drm_connector_funcs intel_dp_connector_funcs = {
.dpms = drm_atomic_helper_connector_dpms,
- .detect = intel_dp_detect,
.force = intel_dp_force,
.fill_modes = drm_helper_probe_single_connector_modes,
.set_property = intel_dp_set_property,
@@ -5027,6 +5023,7 @@ static const struct drm_connector_funcs intel_dp_connector_funcs = {
};
static const struct drm_connector_helper_funcs intel_dp_connector_helper_funcs = {
+ .detect_ctx = intel_dp_detect,
.get_modes = intel_dp_get_modes,
.mode_valid = intel_dp_mode_valid,
};
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 51228fe4283b..fb7afcf9e8be 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1353,10 +1353,10 @@ int ironlake_get_lanes_required(int target_clock, int link_bw, int bpp);
void vlv_wait_port_ready(struct drm_i915_private *dev_priv,
struct intel_digital_port *dport,
unsigned int expected_mask);
-bool intel_get_load_detect_pipe(struct drm_connector *connector,
- struct drm_display_mode *mode,
- struct intel_load_detect_pipe *old,
- struct drm_modeset_acquire_ctx *ctx);
+int intel_get_load_detect_pipe(struct drm_connector *connector,
+ struct drm_display_mode *mode,
+ struct intel_load_detect_pipe *old,
+ struct drm_modeset_acquire_ctx *ctx);
void intel_release_load_detect_pipe(struct drm_connector *connector,
struct intel_load_detect_pipe *old,
struct drm_modeset_acquire_ctx *ctx);
diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
index 7d210097eefa..f1200272a699 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -243,7 +243,8 @@ static bool intel_hpd_irq_event(struct drm_device *dev,
WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
old_status = connector->status;
- connector->status = connector->funcs->detect(connector, false);
+ connector->status = drm_helper_probe_detect(connector, NULL, false);
+
if (old_status == connector->status)
return false;
diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
index 6ed1a3ce47b7..e077c2a9e694 100644
--- a/drivers/gpu/drm/i915/intel_tv.c
+++ b/drivers/gpu/drm/i915/intel_tv.c
@@ -1315,8 +1315,10 @@ static void intel_tv_find_better_format(struct drm_connector *connector)
* Currently this always returns CONNECTOR_STATUS_UNKNOWN, as we need to be sure
* we have a pipe programmed in order to probe the TV.
*/
-static enum drm_connector_status
-intel_tv_detect(struct drm_connector *connector, bool force)
+static int
+intel_tv_detect(struct drm_connector *connector,
+ struct drm_modeset_acquire_ctx *ctx,
+ bool force)
{
struct drm_display_mode mode;
struct intel_tv *intel_tv = intel_attached_tv(connector);
@@ -1331,21 +1333,20 @@ intel_tv_detect(struct drm_connector *connector, bool force)
if (force) {
struct intel_load_detect_pipe tmp;
- struct drm_modeset_acquire_ctx ctx;
+ int ret;
- drm_modeset_acquire_init(&ctx, 0);
+ ret = intel_get_load_detect_pipe(connector, &mode, &tmp, ctx);
+ if (ret < 0)
+ return ret;
- if (intel_get_load_detect_pipe(connector, &mode, &tmp, &ctx)) {
+ if (ret > 0) {
type = intel_tv_detect_type(intel_tv, connector);
- intel_release_load_detect_pipe(connector, &tmp, &ctx);
+ intel_release_load_detect_pipe(connector, &tmp, ctx);
status = type < 0 ?
connector_status_disconnected :
connector_status_connected;
} else
status = connector_status_unknown;
-
- drm_modeset_drop_locks(&ctx);
- drm_modeset_acquire_fini(&ctx);
} else
return connector->status;
@@ -1516,7 +1517,6 @@ out:
static const struct drm_connector_funcs intel_tv_connector_funcs = {
.dpms = drm_atomic_helper_connector_dpms,
- .detect = intel_tv_detect,
.late_register = intel_connector_register,
.early_unregister = intel_connector_unregister,
.destroy = intel_tv_destroy,
@@ -1528,6 +1528,7 @@ static const struct drm_connector_funcs intel_tv_connector_funcs = {
};
static const struct drm_connector_helper_funcs intel_tv_connector_helper_funcs = {
+ .detect_ctx = intel_tv_detect,
.mode_valid = intel_tv_mode_valid,
.get_modes = intel_tv_get_modes,
};
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 941f57f311aa..e2ee74c20b8f 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -32,6 +32,7 @@
struct drm_device;
struct drm_connector_helper_funcs;
+struct drm_modeset_acquire_ctx;
struct drm_device;
struct drm_crtc;
struct drm_encoder;
@@ -378,6 +379,11 @@ struct drm_connector_funcs {
* the helper library vtable purely for historical reasons. The only DRM
* core entry point to probe connector state is @fill_modes.
*
+ * Note that the helper library will already hold
+ * &drm_mode_config.connection_mutex. Drivers which need to grab additional
+ * locks to avoid races with concurrent modeset changes need to use
+ * &drm_connector_helper_funcs.detect_ctx instead.
+ *
* RETURNS:
*
* drm_connector_status indicating the connector's status.
diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h
index 43505c7b2b3f..76e237bd989b 100644
--- a/include/drm/drm_crtc_helper.h
+++ b/include/drm/drm_crtc_helper.h
@@ -67,6 +67,9 @@ int drm_helper_crtc_mode_set_base(struct drm_crtc *crtc, int x, int y,
int drm_helper_probe_single_connector_modes(struct drm_connector
*connector, uint32_t maxX,
uint32_t maxY);
+int drm_helper_probe_detect(struct drm_connector *connector,
+ struct drm_modeset_acquire_ctx *ctx,
+ bool force);
void drm_kms_helper_poll_init(struct drm_device *dev);
void drm_kms_helper_poll_fini(struct drm_device *dev);
bool drm_helper_hpd_irq_event(struct drm_device *dev);
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index 091c42205667..7847babd893c 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -747,6 +747,10 @@ struct drm_connector_helper_funcs {
* This callback is used by the probe helpers in e.g.
* drm_helper_probe_single_connector_modes().
*
+ * To avoid races with concurrent connector state updates, the helper
+ * libraries always call this with the &drm_mode_config.connection_mutex
+ * held. Because of this it's safe to inspect &drm_connector->state.
+ *
* RETURNS:
*
* The number of modes added by calling drm_mode_probed_add().
@@ -754,6 +758,34 @@ struct drm_connector_helper_funcs {
int (*get_modes)(struct drm_connector *connector);
/**
+ * @detect_ctx:
+ *
+ * Check to see if anything is attached to the connector. The parameter
+ * force is set to false whilst polling, true when checking the
+ * connector due to a user request. force can be used by the driver to
+ * avoid expensive, destructive operations during automated probing.
+ *
+ * This callback is optional, if not implemented the connector will be
+ * considered as always being attached.
+ *
+ * This is the atomic version of &drm_connector_funcs.detect.
+ *
+ * To avoid races against concurrent connector state updates, the
+ * helper libraries always call this with ctx set to a valid context,
+ * and &drm_mode_config.connection_mutex will always be locked with
+ * the ctx parameter set to this ctx. This allows taking additional
+ * locks as required.
+ *
+ * RETURNS:
+ *
+ * &drm_connector_status indicating the connector's status,
+ * or the error code returned by drm_modeset_lock(), -EDEADLK.
+ */
+ int (*detect_ctx)(struct drm_connector *connector,
+ struct drm_modeset_acquire_ctx *ctx,
+ bool force);
+
+ /**
* @mode_valid:
*
* Callback to validate a mode for a connector, irrespective of the
@@ -771,6 +803,10 @@ struct drm_connector_helper_funcs {
* CRTC helpers will not call this function. Drivers therefore must
* still fully validate any mode passed in in a modeset request.
*
+ * To avoid races with concurrent connector state updates, the helper
+ * libraries always call this with the &drm_mode_config.connection_mutex
+ * held. Because of this it's safe to inspect &drm_connector->state.
+ *
* RETURNS:
*
* Either &drm_mode_status.MODE_OK or one of the failure reasons in &enum