[PATCH v2 1/2] drm/i915/dp_mst: Cast intel_connector->port as drm_dp_mst_port

[PATCH v2 1/2] drm/i915/dp_mst: Cast intel_connector->port as drm_dp_mst_port

[Lyude Paul]

The only reason for having this cast as void * before was because we
originally needed to use drm_dp_mst_get_port_validated() and friends in
order to (attempt to) safely access MST ports. However, we've since
improved how reference counting works with ports and mstbs such that we
can now rely on drm_dp_mst_port structs remaining in memory for as long
as the driver needs. This means we don't really need to cast this as
void* anymore, and can just access the struct directly.

We'll also need this for the next commit, so that we can remove
drm_dp_mst_port_has_audio().

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Sean Paul <sean@poorly.run>
---
 drivers/gpu/drm/i915/display/intel_display_types.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 5a0adf14ebef..0ddc98afe252 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -438,7 +438,7 @@ struct intel_connector {
 	   state of connector->polled in case hotplug storm detection changes it */
 	u8 polled;
 
-	void *port; /* store this opaque as its illegal to dereference it */
+	struct drm_dp_mst_port *port;
 
 	struct intel_dp *mst_port;
 
-- 
2.25.1

[PATCH v2 2/2] drm/dp_mst: Remove drm_dp_mst_has_audio()

[Lyude Paul]

Drive-by fix I noticed the other day - drm_dp_mst_has_audio() only ever
made sense back when we still had to validate ports before accessing
them in order to (attempt to) avoid NULL dereferences. Since we have
proper reference counting that guarantees we always can safely access
the MST port, there's no use in keeping this function around as all it
does is validate the port pointer before checking the audio status.

Note - drm_dp_mst_port->has_audio is technically protected by
drm_device->mode_config.connection_mutex, since it's only ever updated
from drm_dp_mst_get_edid(). Additionally, we change the declaration for
port in struct intel_connector to be properly typed, so we can directly
access it.

Changes since v1:
* Change type of intel_connector->port in a separate patch - Sean Paul

Cc: "Lee, Shawn C" <shawn.c.lee@intel.com>
Reviewed-by: Sean Paul <sean@poorly.run>
Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c         | 21 -------------------
 .../drm/i915/display/intel_display_debugfs.c  | 10 ++-------
 drivers/gpu/drm/i915/display/intel_dp_mst.c   |  3 +--
 include/drm/drm_dp_mst_helper.h               |  2 --
 4 files changed, 3 insertions(+), 33 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 5b205aea58d4..8289d59b62da 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4063,27 +4063,6 @@ drm_dp_mst_detect_port(struct drm_connector *connector,
 }
 EXPORT_SYMBOL(drm_dp_mst_detect_port);
 
-/**
- * drm_dp_mst_port_has_audio() - Check whether port has audio capability or not
- * @mgr: manager for this port
- * @port: unverified pointer to a port.
- *
- * This returns whether the port supports audio or not.
- */
-bool drm_dp_mst_port_has_audio(struct drm_dp_mst_topology_mgr *mgr,
-					struct drm_dp_mst_port *port)
-{
-	bool ret = false;
-
-	port = drm_dp_mst_topology_get_port_validated(mgr, port);
-	if (!port)
-		return ret;
-	ret = port->has_audio;
-	drm_dp_mst_topology_put_port(port);
-	return ret;
-}
-EXPORT_SYMBOL(drm_dp_mst_port_has_audio);
-
 /**
  * drm_dp_mst_get_edid() - get EDID for an MST port
  * @connector: toplevel connector to get EDID for
diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
index 424f4e52f783..9f736420d83f 100644
--- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
+++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
@@ -631,15 +631,9 @@ static void intel_dp_info(struct seq_file *m,
 }
 
 static void intel_dp_mst_info(struct seq_file *m,
-			  struct intel_connector *intel_connector)
+			      struct intel_connector *intel_connector)
 {
-	struct intel_encoder *intel_encoder = intel_attached_encoder(intel_connector);
-	struct intel_dp_mst_encoder *intel_mst =
-		enc_to_mst(intel_encoder);
-	struct intel_digital_port *intel_dig_port = intel_mst->primary;
-	struct intel_dp *intel_dp = &intel_dig_port->dp;
-	bool has_audio = drm_dp_mst_port_has_audio(&intel_dp->mst_mgr,
-					intel_connector->port);
+	bool has_audio = intel_connector->port->has_audio;
 
 	seq_printf(m, "\taudio support: %s\n", yesno(has_audio));
 }
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 61605eb8c2af..c35efc9e628d 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -114,8 +114,7 @@ static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
 
 	if (intel_conn_state->force_audio == HDMI_AUDIO_AUTO)
 		pipe_config->has_audio =
-			drm_dp_mst_port_has_audio(&intel_dp->mst_mgr,
-						  connector->port);
+			connector->port->has_audio;
 	else
 		pipe_config->has_audio =
 			intel_conn_state->force_audio == HDMI_AUDIO_ON;
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 7af51c947b81..2d7c26592c05 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -732,8 +732,6 @@ drm_dp_mst_detect_port(struct drm_connector *connector,
 		       struct drm_dp_mst_topology_mgr *mgr,
 		       struct drm_dp_mst_port *port);
 
-bool drm_dp_mst_port_has_audio(struct drm_dp_mst_topology_mgr *mgr,
-					struct drm_dp_mst_port *port);
 struct edid *drm_dp_mst_get_edid(struct drm_connector *connector, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port);
 
 
-- 
2.25.1

Re: [PATCH v2 1/2] drm/i915/dp_mst: Cast intel_connector->port as drm_dp_mst_port

[Jani Nikula]

On Mon, 06 Apr 2020, Lyude Paul <lyude@redhat.com> wrote:
> The only reason for having this cast as void * before was because we
> originally needed to use drm_dp_mst_get_port_validated() and friends in
> order to (attempt to) safely access MST ports. However, we've since
> improved how reference counting works with ports and mstbs such that we
> can now rely on drm_dp_mst_port structs remaining in memory for as long
> as the driver needs. This means we don't really need to cast this as
> void* anymore, and can just access the struct directly.

To/from void* does not need a cast in C anyway. ;)

Acked-by: Jani Nikula <jani.nikula@intel.com>

>
> We'll also need this for the next commit, so that we can remove
> drm_dp_mst_port_has_audio().
>
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Reviewed-by: Sean Paul <sean@poorly.run>
> ---
>  drivers/gpu/drm/i915/display/intel_display_types.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index 5a0adf14ebef..0ddc98afe252 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -438,7 +438,7 @@ struct intel_connector {
>  	   state of connector->polled in case hotplug storm detection changes it */
>  	u8 polled;
>  
> -	void *port; /* store this opaque as its illegal to dereference it */
> +	struct drm_dp_mst_port *port;
>  
>  	struct intel_dp *mst_port;

-- 
Jani Nikula, Intel Open Source Graphics Center