[PATCH] drm/dp_mst: Remove drm_dp_mst_has_audio()

[PATCH] 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.

Cc: "Lee, Shawn C" <shawn.c.lee@intel.com>
Cc: 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 ++-------
 .../drm/i915/display/intel_display_types.h    |  2 +-
 drivers/gpu/drm/i915/display/intel_dp_mst.c   |  3 +--
 include/drm/drm_dp_mst_helper.h               |  2 --
 5 files changed, 4 insertions(+), 34 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 1ff49547b2e8..129126091e90 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_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 2bedd626c686..1de7bef0a49b 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -436,7 +436,7 @@ 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;
 
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] drm/dp_mst: Remove drm_dp_mst_has_audio()

[Sean Paul]

On Fri, Apr 3, 2020 at 6:23 PM Lyude Paul <lyude@redhat.com> wrote:
>
> 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.
>

This is kind of burying the lede. I'd almost prefer a 2 patch series:

drm/i915: Allow connectors to directly access drm_dp_mst_port
drm/dp_mst: Remove unused drm_dp_mst_port_has_audio()

That way if anyone objects to the idea of accessing mst_port directly
from i915 driver, it's more obvious from the patch subject.

Nitpicks aside, the code looks good to me, it's a nice cleanup!

Reviewed-by: Sean Paul <sean@poorly.run>

> Cc: "Lee, Shawn C" <shawn.c.lee@intel.com>
> Cc: 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 ++-------
>  .../drm/i915/display/intel_display_types.h    |  2 +-
>  drivers/gpu/drm/i915/display/intel_dp_mst.c   |  3 +--
>  include/drm/drm_dp_mst_helper.h               |  2 --
>  5 files changed, 4 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 1ff49547b2e8..129126091e90 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_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index 2bedd626c686..1de7bef0a49b 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -436,7 +436,7 @@ 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;
>
> 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
>