diff mbox series

[RFCv5,3/4] media: add functions to add properties to objects

Message ID 20181213134113.15247-4-hverkuil-cisco@xs4all.nl (mailing list archive)
State New, archived
Headers show
Series Add properties support to the media controller | expand

Commit Message

Hans Verkuil Dec. 13, 2018, 1:41 p.m. UTC 
From: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Add functions to add properties to entities, pads and other
properties. This can be extended to include interfaces and links
in the future when needed.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
---
 drivers/media/media-entity.c |  64 +++++++++
 include/media/media-entity.h | 264 +++++++++++++++++++++++++++++++++++
 2 files changed, 328 insertions(+)

Comments

Mauro Carvalho Chehab Dec. 13, 2018, 5:30 p.m. UTC | #1 
Em Thu, 13 Dec 2018 14:41:12 +0100
hverkuil-cisco@xs4all.nl escreveu:

> From: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> 
> Add functions to add properties to entities, pads and other
> properties. This can be extended to include interfaces and links
> in the future when needed.
> 
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> ---
>  drivers/media/media-entity.c |  64 +++++++++
>  include/media/media-entity.h | 264 +++++++++++++++++++++++++++++++++++
>  2 files changed, 328 insertions(+)
> 
> diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c
> index 62c4d5b4d33f..cdb35bc8e9a0 100644
> --- a/drivers/media/media-entity.c
> +++ b/drivers/media/media-entity.c
> @@ -251,6 +251,70 @@ int media_entity_pads_init(struct media_entity *entity, u16 num_pads,
>  }
>  EXPORT_SYMBOL_GPL(media_entity_pads_init);
>  
> +static struct media_prop *media_create_prop(struct media_gobj *owner, u32 type,
> +					    const char *name, const void *ptr,
> +					    u32 payload_size)
> +{
> +	struct media_prop *prop = kzalloc(sizeof(*prop) + payload_size,
> +					  GFP_KERNEL);
> +
> +	if (!prop)
> +		return ERR_PTR(-ENOMEM);
> +	prop->type = type;
> +	strscpy(prop->name, name, sizeof(prop->name));
> +	if (owner->mdev)
> +		media_gobj_create(owner->mdev, MEDIA_GRAPH_PROP,
> +				  &prop->graph_obj);
> +	prop->owner = owner;
> +	prop->payload_size = payload_size;
> +	if (payload_size && ptr)
> +		memcpy(prop->payload, ptr, payload_size);
> +	INIT_LIST_HEAD(&prop->props);
> +	return prop;
> +}
> +
> +struct media_prop *media_entity_add_prop(struct media_entity *ent, u32 type,
> +					 const char *name, const void *ptr,
> +					 u32 payload_size)
> +{
> +	struct media_prop *prop;
> +
> +	if (!ent->inited)
> +		media_entity_init(ent);
> +	prop = media_create_prop(&ent->graph_obj, type,
> +				 name, ptr, payload_size);
> +	if (!IS_ERR(prop))
> +		list_add_tail(&prop->list, &ent->props);
> +	return prop;
> +}
> +EXPORT_SYMBOL_GPL(media_entity_add_prop);
> +
> +struct media_prop *media_pad_add_prop(struct media_pad *pad, u32 type,
> +				      const char *name, const void *ptr,
> +				      u32 payload_size)
> +{
> +	struct media_prop *prop = media_create_prop(&pad->graph_obj, type,
> +						    name, ptr, payload_size);
> +
> +	if (!IS_ERR(prop))
> +		list_add_tail(&prop->list, &pad->props);
> +	return prop;
> +}
> +EXPORT_SYMBOL_GPL(media_pad_add_prop);
> +
> +struct media_prop *media_prop_add_prop(struct media_prop *prop, u32 type,
> +				       const char *name, const void *ptr,
> +				       u32 payload_size)
> +{
> +	struct media_prop *subprop = media_create_prop(&prop->graph_obj, type,
> +						       name, ptr, payload_size);
> +
> +	if (!IS_ERR(subprop))
> +		list_add_tail(&subprop->list, &prop->props);
> +	return subprop;
> +}
> +EXPORT_SYMBOL_GPL(media_prop_add_prop);
> +
>  /* -----------------------------------------------------------------------------
>   * Graph traversal
>   */
> diff --git a/include/media/media-entity.h b/include/media/media-entity.h
> index 5d05ebf712d0..695acfd3fe9c 100644
> --- a/include/media/media-entity.h
> +++ b/include/media/media-entity.h
> @@ -833,6 +833,270 @@ int media_create_pad_links(const struct media_device *mdev,
>  
>  void __media_entity_remove_links(struct media_entity *entity);
>  
> +/**
> + * media_entity_add_prop() - Add property to entity
> + *
> + * @entity:	entity where to add the property
> + * @type:	property type
> + * @name:	property name
> + * @ptr:	property pointer to payload
> + * @payload_size: property payload size
> + *
> + * Returns the new property on success, or an error pointer on failure.
> + */
> +struct media_prop *media_entity_add_prop(struct media_entity *ent, u32 type,
> +					 const char *name, const void *ptr,
> +					 u32 payload_size);
> +
> +/**
> + * media_pad_add_prop() - Add property to pad
> + *
> + * @pad:	pad where to add the property
> + * @type:	property type
> + * @name:	property name
> + * @ptr:	property pointer to payload
> + * @payload_size: property payload size
> + *
> + * Returns the new property on success, or an error pointer on failure.
> + */
> +struct media_prop *media_pad_add_prop(struct media_pad *pad, u32 type,
> +				      const char *name, const void *ptr,
> +				      u32 payload_size);
> +
> +/**
> + * media_prop() - Add sub-property to property
> + *
> + * @prop:	property where to add the sub-property
> + * @type:	sub-property type
> + * @name:	sub-property name
> + * @ptr:	sub-property pointer to payload
> + * @payload_size: sub-property payload size
> + *
> + * Returns the new property on success, or an error pointer on failure.
> + */
> +struct media_prop *media_prop_add_prop(struct media_prop *prop, u32 type,
> +				       const char *name, const void *ptr,
> +				       u32 payload_size);
> +
> +/**
> + * media_entity_add_prop_group() - Add group property to entity
> + *
> + * @entity:	entity where to add the property
> + * @name:	property name
> + *
> + * Returns the new property on success, or an error pointer on failure.
> + */
> +static inline struct media_prop *
> +media_entity_add_prop_group(struct media_entity *entity, const char *name)
> +{
> +	return media_entity_add_prop(entity, MEDIA_PROP_TYPE_GROUP,
> +				     name, NULL, 0);
> +}

Hmm... group is just a string? On my past comments for patches 1/4 and 2/4
I assumed it would be an u32 array :-)

That's btw why I asked you to add some documentation. That would avoid
reviewers of guessing some things ;-)

Why are you using zero for the payload? At patch 1/4, you said that
only u64 and s64 would have payload_size == 0:

	+ * @payload_size: Property payload size, 0 for U64/S64

One would infer that, for all other types, payload_size would be
a non-zero value.

> +
> +/**
> + * media_entity_add_prop_u64() - Add u64 property to entity
> + *
> + * @entity:	entity where to add the property
> + * @name:	property name
> + * @val:	property value
> + *
> + * Returns 0 on success, or an error on failure.
> + */
> +static inline int media_entity_add_prop_u64(struct media_entity *entity,
> +					    const char *name, u64 val)
> +{
> +	struct media_prop *prop =
> +		media_entity_add_prop(entity, MEDIA_PROP_TYPE_U64,
> +				      name, &val, sizeof(val));
> +
> +	return PTR_ERR_OR_ZERO(prop);
> +}
> +
> +/**
> + * media_entity_add_prop_s64() - Add s64 property to entity
> + *
> + * @entity:	entity where to add the property
> + * @name:	property name
> + * @val:	property value
> + *
> + * Returns 0 on success, or an error on failure.
> + */
> +static inline int media_entity_add_prop_s64(struct media_entity *entity,
> +					    const char *name, s64 val)
> +{
> +	struct media_prop *prop =
> +		media_entity_add_prop(entity, MEDIA_PROP_TYPE_S64,
> +				      name, &val, sizeof(val));
> +
> +	return PTR_ERR_OR_ZERO(prop);
> +}
> +
> +/**
> + * media_entity_add_prop_string() - Add string property to entity
> + *
> + * @entity:	entity where to add the property
> + * @name:	property name
> + * @string:	property string value
> + *
> + * Returns 0 on success, or an error on failure.
> + */
> +static inline int media_entity_add_prop_string(struct media_entity *entity,
> +					       const char *name,
> +					       const char *string)
> +{
> +	struct media_prop *prop =
> +		media_entity_add_prop(entity, MEDIA_PROP_TYPE_STRING,
> +				      name, string, strlen(string) + 1);

Ok, so, you're assuming that, for strings, payload_type will include
the ending '\0' character, and that strings are NUL-terminated.

Please document it, as we usually have NUL-terminated strings OR
LEN + string. Having both is non-trivial.

> +
> +	return PTR_ERR_OR_ZERO(prop);
> +}
> +
> +/**
> + * media_pad_add_prop_group() - Add group property to pad
> + *
> + * @pad:	pad where to add the property
> + * @name:	property name
> + *
> + * Returns the new property on success, or an error pointer on failure.
> + */
> +static inline struct media_prop *media_pad_add_prop_group(struct media_pad *pad,
> +							  const char *name)
> +{
> +	return media_pad_add_prop(pad, MEDIA_PROP_TYPE_GROUP,
> +				  name, NULL, 0);
> +}
> +
> +/**
> + * media_pad_add_prop_u64() - Add u64 property to pad
> + *
> + * @pad:	pad where to add the property
> + * @name:	property name
> + * @val:	property value
> + *
> + * Returns 0 on success, or an error on failure.
> + */
> +static inline int media_pad_add_prop_u64(struct media_pad *pad,
> +					 const char *name, u64 val)
> +{
> +	struct media_prop *prop =
> +		media_pad_add_prop(pad, MEDIA_PROP_TYPE_U64,
> +				   name, &val, sizeof(val));
> +
> +	return PTR_ERR_OR_ZERO(prop);
> +}
> +
> +/**
> + * media_pad_add_prop_s64() - Add s64 property to pad
> + *
> + * @pad:	pad where to add the property
> + * @name:	property name
> + * @val:	property value
> + *
> + * Returns 0 on success, or an error on failure.
> + */
> +static inline int media_pad_add_prop_s64(struct media_pad *pad,
> +					 const char *name, s64 val)
> +{
> +	struct media_prop *prop =
> +		media_pad_add_prop(pad, MEDIA_PROP_TYPE_S64,
> +				   name, &val, sizeof(val));
> +
> +	return PTR_ERR_OR_ZERO(prop);
> +}
> +
> +/**
> + * media_pad_add_prop_string() - Add string property to pad
> + *
> + * @pad:	pad where to add the property
> + * @name:	property name
> + * @string:	property string value
> + *
> + * Returns 0 on success, or an error on failure.
> + */
> +static inline int media_pad_add_prop_string(struct media_pad *pad,
> +					    const char *name,
> +					    const char *string)
> +{
> +	struct media_prop *prop =
> +		media_pad_add_prop(pad, MEDIA_PROP_TYPE_STRING,
> +				   name, string, strlen(string) + 1);
> +
> +	return PTR_ERR_OR_ZERO(prop);
> +}
> +
> +/**
> + * media_prop_add_prop_group() - Add group sub-property to property
> + *
> + * @prop:	property where to add the sub-property
> + * @name:	sub-property name
> + *
> + * Returns the new property on success, or an error pointer on failure.
> + */
> +static inline struct media_prop *
> +media_prop_add_prop_group(struct media_prop *prop, const char *name)
> +{
> +	return media_prop_add_prop(prop, MEDIA_PROP_TYPE_GROUP,
> +				  name, NULL, 0);
> +}
> +
> +/**
> + * media_prop_add_prop_u64() - Add u64 property to property
> + *
> + * @prop:	property where to add the sub-property
> + * @name:	sub-property name
> + * @val:	sub-property value
> + *
> + * Returns 0 on success, or an error on failure.
> + */
> +static inline int media_prop_add_prop_u64(struct media_prop *prop,
> +					  const char *name, u64 val)
> +{
> +	struct media_prop *subprop =
> +		media_prop_add_prop(prop, MEDIA_PROP_TYPE_U64,
> +				    name, &val, sizeof(val));
> +
> +	return PTR_ERR_OR_ZERO(subprop);
> +}
> +
> +/**
> + * media_prop_add_prop_s64() - Add s64 property to property
> + *
> + * @prop:	property where to add the sub-property
> + * @name:	sub-property name
> + * @val:	sub-property value
> + *
> + * Returns 0 on success, or an error on failure.
> + */
> +static inline int media_prop_add_prop_s64(struct media_prop *prop,
> +					  const char *name, s64 val)
> +{
> +	struct media_prop *subprop =
> +		media_prop_add_prop(prop, MEDIA_PROP_TYPE_S64,
> +				    name, &val, sizeof(val));
> +
> +	return PTR_ERR_OR_ZERO(subprop);
> +}
> +
> +/**
> + * media_prop_add_prop_string() - Add string property to property
> + *
> + * @prop:	property where to add the sub-property
> + * @name:	sub-property name
> + * @string:	sub-property string value
> + *
> + * Returns 0 on success, or an error on failure.
> + */
> +static inline int media_prop_add_prop_string(struct media_prop *prop,
> +					     const char *name,
> +					     const char *string)
> +{
> +	struct media_prop *subprop =
> +		media_prop_add_prop(prop, MEDIA_PROP_TYPE_STRING,
> +				    name, string, strlen(string) + 1);
> +
> +	return PTR_ERR_OR_ZERO(subprop);
> +}
> +
>  /**
>   * media_entity_remove_links() - remove all links associated with an entity
>   *



Thanks,
Mauro
diff mbox series

Patch

diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c
index 62c4d5b4d33f..cdb35bc8e9a0 100644
--- a/drivers/media/media-entity.c
+++ b/drivers/media/media-entity.c
@@ -251,6 +251,70 @@  int media_entity_pads_init(struct media_entity *entity, u16 num_pads,
 }
 EXPORT_SYMBOL_GPL(media_entity_pads_init);
 
+static struct media_prop *media_create_prop(struct media_gobj *owner, u32 type,
+					    const char *name, const void *ptr,
+					    u32 payload_size)
+{
+	struct media_prop *prop = kzalloc(sizeof(*prop) + payload_size,
+					  GFP_KERNEL);
+
+	if (!prop)
+		return ERR_PTR(-ENOMEM);
+	prop->type = type;
+	strscpy(prop->name, name, sizeof(prop->name));
+	if (owner->mdev)
+		media_gobj_create(owner->mdev, MEDIA_GRAPH_PROP,
+				  &prop->graph_obj);
+	prop->owner = owner;
+	prop->payload_size = payload_size;
+	if (payload_size && ptr)
+		memcpy(prop->payload, ptr, payload_size);
+	INIT_LIST_HEAD(&prop->props);
+	return prop;
+}
+
+struct media_prop *media_entity_add_prop(struct media_entity *ent, u32 type,
+					 const char *name, const void *ptr,
+					 u32 payload_size)
+{
+	struct media_prop *prop;
+
+	if (!ent->inited)
+		media_entity_init(ent);
+	prop = media_create_prop(&ent->graph_obj, type,
+				 name, ptr, payload_size);
+	if (!IS_ERR(prop))
+		list_add_tail(&prop->list, &ent->props);
+	return prop;
+}
+EXPORT_SYMBOL_GPL(media_entity_add_prop);
+
+struct media_prop *media_pad_add_prop(struct media_pad *pad, u32 type,
+				      const char *name, const void *ptr,
+				      u32 payload_size)
+{
+	struct media_prop *prop = media_create_prop(&pad->graph_obj, type,
+						    name, ptr, payload_size);
+
+	if (!IS_ERR(prop))
+		list_add_tail(&prop->list, &pad->props);
+	return prop;
+}
+EXPORT_SYMBOL_GPL(media_pad_add_prop);
+
+struct media_prop *media_prop_add_prop(struct media_prop *prop, u32 type,
+				       const char *name, const void *ptr,
+				       u32 payload_size)
+{
+	struct media_prop *subprop = media_create_prop(&prop->graph_obj, type,
+						       name, ptr, payload_size);
+
+	if (!IS_ERR(subprop))
+		list_add_tail(&subprop->list, &prop->props);
+	return subprop;
+}
+EXPORT_SYMBOL_GPL(media_prop_add_prop);
+
 /* -----------------------------------------------------------------------------
  * Graph traversal
  */
diff --git a/include/media/media-entity.h b/include/media/media-entity.h
index 5d05ebf712d0..695acfd3fe9c 100644
--- a/include/media/media-entity.h
+++ b/include/media/media-entity.h
@@ -833,6 +833,270 @@  int media_create_pad_links(const struct media_device *mdev,
 
 void __media_entity_remove_links(struct media_entity *entity);
 
+/**
+ * media_entity_add_prop() - Add property to entity
+ *
+ * @entity:	entity where to add the property
+ * @type:	property type
+ * @name:	property name
+ * @ptr:	property pointer to payload
+ * @payload_size: property payload size
+ *
+ * Returns the new property on success, or an error pointer on failure.
+ */
+struct media_prop *media_entity_add_prop(struct media_entity *ent, u32 type,
+					 const char *name, const void *ptr,
+					 u32 payload_size);
+
+/**
+ * media_pad_add_prop() - Add property to pad
+ *
+ * @pad:	pad where to add the property
+ * @type:	property type
+ * @name:	property name
+ * @ptr:	property pointer to payload
+ * @payload_size: property payload size
+ *
+ * Returns the new property on success, or an error pointer on failure.
+ */
+struct media_prop *media_pad_add_prop(struct media_pad *pad, u32 type,
+				      const char *name, const void *ptr,
+				      u32 payload_size);
+
+/**
+ * media_prop() - Add sub-property to property
+ *
+ * @prop:	property where to add the sub-property
+ * @type:	sub-property type
+ * @name:	sub-property name
+ * @ptr:	sub-property pointer to payload
+ * @payload_size: sub-property payload size
+ *
+ * Returns the new property on success, or an error pointer on failure.
+ */
+struct media_prop *media_prop_add_prop(struct media_prop *prop, u32 type,
+				       const char *name, const void *ptr,
+				       u32 payload_size);
+
+/**
+ * media_entity_add_prop_group() - Add group property to entity
+ *
+ * @entity:	entity where to add the property
+ * @name:	property name
+ *
+ * Returns the new property on success, or an error pointer on failure.
+ */
+static inline struct media_prop *
+media_entity_add_prop_group(struct media_entity *entity, const char *name)
+{
+	return media_entity_add_prop(entity, MEDIA_PROP_TYPE_GROUP,
+				     name, NULL, 0);
+}
+
+/**
+ * media_entity_add_prop_u64() - Add u64 property to entity
+ *
+ * @entity:	entity where to add the property
+ * @name:	property name
+ * @val:	property value
+ *
+ * Returns 0 on success, or an error on failure.
+ */
+static inline int media_entity_add_prop_u64(struct media_entity *entity,
+					    const char *name, u64 val)
+{
+	struct media_prop *prop =
+		media_entity_add_prop(entity, MEDIA_PROP_TYPE_U64,
+				      name, &val, sizeof(val));
+
+	return PTR_ERR_OR_ZERO(prop);
+}
+
+/**
+ * media_entity_add_prop_s64() - Add s64 property to entity
+ *
+ * @entity:	entity where to add the property
+ * @name:	property name
+ * @val:	property value
+ *
+ * Returns 0 on success, or an error on failure.
+ */
+static inline int media_entity_add_prop_s64(struct media_entity *entity,
+					    const char *name, s64 val)
+{
+	struct media_prop *prop =
+		media_entity_add_prop(entity, MEDIA_PROP_TYPE_S64,
+				      name, &val, sizeof(val));
+
+	return PTR_ERR_OR_ZERO(prop);
+}
+
+/**
+ * media_entity_add_prop_string() - Add string property to entity
+ *
+ * @entity:	entity where to add the property
+ * @name:	property name
+ * @string:	property string value
+ *
+ * Returns 0 on success, or an error on failure.
+ */
+static inline int media_entity_add_prop_string(struct media_entity *entity,
+					       const char *name,
+					       const char *string)
+{
+	struct media_prop *prop =
+		media_entity_add_prop(entity, MEDIA_PROP_TYPE_STRING,
+				      name, string, strlen(string) + 1);
+
+	return PTR_ERR_OR_ZERO(prop);
+}
+
+/**
+ * media_pad_add_prop_group() - Add group property to pad
+ *
+ * @pad:	pad where to add the property
+ * @name:	property name
+ *
+ * Returns the new property on success, or an error pointer on failure.
+ */
+static inline struct media_prop *media_pad_add_prop_group(struct media_pad *pad,
+							  const char *name)
+{
+	return media_pad_add_prop(pad, MEDIA_PROP_TYPE_GROUP,
+				  name, NULL, 0);
+}
+
+/**
+ * media_pad_add_prop_u64() - Add u64 property to pad
+ *
+ * @pad:	pad where to add the property
+ * @name:	property name
+ * @val:	property value
+ *
+ * Returns 0 on success, or an error on failure.
+ */
+static inline int media_pad_add_prop_u64(struct media_pad *pad,
+					 const char *name, u64 val)
+{
+	struct media_prop *prop =
+		media_pad_add_prop(pad, MEDIA_PROP_TYPE_U64,
+				   name, &val, sizeof(val));
+
+	return PTR_ERR_OR_ZERO(prop);
+}
+
+/**
+ * media_pad_add_prop_s64() - Add s64 property to pad
+ *
+ * @pad:	pad where to add the property
+ * @name:	property name
+ * @val:	property value
+ *
+ * Returns 0 on success, or an error on failure.
+ */
+static inline int media_pad_add_prop_s64(struct media_pad *pad,
+					 const char *name, s64 val)
+{
+	struct media_prop *prop =
+		media_pad_add_prop(pad, MEDIA_PROP_TYPE_S64,
+				   name, &val, sizeof(val));
+
+	return PTR_ERR_OR_ZERO(prop);
+}
+
+/**
+ * media_pad_add_prop_string() - Add string property to pad
+ *
+ * @pad:	pad where to add the property
+ * @name:	property name
+ * @string:	property string value
+ *
+ * Returns 0 on success, or an error on failure.
+ */
+static inline int media_pad_add_prop_string(struct media_pad *pad,
+					    const char *name,
+					    const char *string)
+{
+	struct media_prop *prop =
+		media_pad_add_prop(pad, MEDIA_PROP_TYPE_STRING,
+				   name, string, strlen(string) + 1);
+
+	return PTR_ERR_OR_ZERO(prop);
+}
+
+/**
+ * media_prop_add_prop_group() - Add group sub-property to property
+ *
+ * @prop:	property where to add the sub-property
+ * @name:	sub-property name
+ *
+ * Returns the new property on success, or an error pointer on failure.
+ */
+static inline struct media_prop *
+media_prop_add_prop_group(struct media_prop *prop, const char *name)
+{
+	return media_prop_add_prop(prop, MEDIA_PROP_TYPE_GROUP,
+				  name, NULL, 0);
+}
+
+/**
+ * media_prop_add_prop_u64() - Add u64 property to property
+ *
+ * @prop:	property where to add the sub-property
+ * @name:	sub-property name
+ * @val:	sub-property value
+ *
+ * Returns 0 on success, or an error on failure.
+ */
+static inline int media_prop_add_prop_u64(struct media_prop *prop,
+					  const char *name, u64 val)
+{
+	struct media_prop *subprop =
+		media_prop_add_prop(prop, MEDIA_PROP_TYPE_U64,
+				    name, &val, sizeof(val));
+
+	return PTR_ERR_OR_ZERO(subprop);
+}
+
+/**
+ * media_prop_add_prop_s64() - Add s64 property to property
+ *
+ * @prop:	property where to add the sub-property
+ * @name:	sub-property name
+ * @val:	sub-property value
+ *
+ * Returns 0 on success, or an error on failure.
+ */
+static inline int media_prop_add_prop_s64(struct media_prop *prop,
+					  const char *name, s64 val)
+{
+	struct media_prop *subprop =
+		media_prop_add_prop(prop, MEDIA_PROP_TYPE_S64,
+				    name, &val, sizeof(val));
+
+	return PTR_ERR_OR_ZERO(subprop);
+}
+
+/**
+ * media_prop_add_prop_string() - Add string property to property
+ *
+ * @prop:	property where to add the sub-property
+ * @name:	sub-property name
+ * @string:	sub-property string value
+ *
+ * Returns 0 on success, or an error on failure.
+ */
+static inline int media_prop_add_prop_string(struct media_prop *prop,
+					     const char *name,
+					     const char *string)
+{
+	struct media_prop *subprop =
+		media_prop_add_prop(prop, MEDIA_PROP_TYPE_STRING,
+				    name, string, strlen(string) + 1);
+
+	return PTR_ERR_OR_ZERO(subprop);
+}
+
 /**
  * media_entity_remove_links() - remove all links associated with an entity
  *