control: ucm: add ioctl to retrieve full card components

The fixed-size components field in SNDRV_CTL_IOCTL_CARD_INFO can be too
small on systems with many audio devices. The kernel [1] will provide a
new ioctl to read the full string while truncating the original in
card_info if it grows too big. Make sure the code falls back to original
if the new ioctl is not supported.

[1]: https://lore.kernel.org/all/20260122111249.67319-1-mstrozek@opensource.cirrus.com/
Signed-off-by: Maciej Strozek <mstrozek@opensource.cirrus.com>

Author: mstrozek

aserver/aserver.c

@@ -647,6 +647,9 @@ static int ctl_shm_cmd(client_t *client)
 	case SNDRV_CTL_IOCTL_CARD_INFO:
 		ctrl->result = snd_ctl_card_info(ctl, &ctrl->u.card_info);
 		break;
+	case SNDRV_CTL_IOCTL_CARD_COMPONENTS:
+		ctrl->result = snd_ctl_card_components(ctl, &ctrl->u.card_components);
+		break;
 	case SNDRV_CTL_IOCTL_ELEM_LIST:
 	{
 		size_t maxsize = CTL_SHM_DATA_MAXLEN;

include/aserver.h

@@ -123,6 +123,7 @@ typedef struct {
 		int device;
 		int subscribe_events;
 		snd_ctl_card_info_t card_info;
+		snd_ctl_card_components_t card_components;
 		snd_ctl_elem_list_t element_list;
 		snd_ctl_elem_info_t element_info;
 		snd_ctl_elem_value_t element_read;

include/control.h

@@ -84,6 +84,11 @@ typedef struct snd_aes_iec958 {
  */
 typedef struct _snd_ctl_card_info snd_ctl_card_info_t;
 
+/**
+ * \brief CTL card components container.
+ */
+typedef struct _snd_ctl_card_components snd_ctl_card_components_t;
+
 /** CTL element identifier container */
 typedef struct _snd_ctl_elem_id snd_ctl_elem_id_t;
 
@@ -394,6 +399,7 @@ int snd_ctl_poll_descriptors(snd_ctl_t *ctl, struct pollfd *pfds, unsigned int s
 int snd_ctl_poll_descriptors_revents(snd_ctl_t *ctl, struct pollfd *pfds, unsigned int nfds, unsigned short *revents);
 int snd_ctl_subscribe_events(snd_ctl_t *ctl, int subscribe);
 int snd_ctl_card_info(snd_ctl_t *ctl, snd_ctl_card_info_t *info);
+int snd_ctl_card_components(snd_ctl_t *ctl, snd_ctl_card_components_t *components);
 int snd_ctl_elem_list(snd_ctl_t *ctl, snd_ctl_elem_list_t *list);
 int snd_ctl_elem_info(snd_ctl_t *ctl, snd_ctl_elem_info_t *info);
 int snd_ctl_elem_read(snd_ctl_t *ctl, snd_ctl_elem_value_t *data);
@@ -508,6 +514,22 @@ const char *snd_ctl_card_info_get_longname(const snd_ctl_card_info_t *obj);
 const char *snd_ctl_card_info_get_mixername(const snd_ctl_card_info_t *obj);
 const char *snd_ctl_card_info_get_components(const snd_ctl_card_info_t *obj);
 
+size_t snd_ctl_card_components_sizeof(void);
+/** \hideinitializer
+ * \brief allocate an invalid #snd_ctl_card_components_t using standard alloca
+ * \param ptr returned pointer
+ */
+#define snd_ctl_card_components_alloca(ptr) __snd_alloca(ptr, snd_ctl_card_components)
+int snd_ctl_card_components_malloc(snd_ctl_card_components_t **ptr);
+void snd_ctl_card_components_free(snd_ctl_card_components_t *obj);
+void snd_ctl_card_components_clear(snd_ctl_card_components_t *obj);
+void snd_ctl_card_components_copy(snd_ctl_card_components_t *dst, const snd_ctl_card_components_t *src);
+int snd_ctl_card_components_get_card(const snd_ctl_card_components_t *obj);
+unsigned int snd_ctl_card_components_get_length(const snd_ctl_card_components_t *obj);
+const char *snd_ctl_card_components_get_string(const snd_ctl_card_components_t *obj);
+
+size_t snd_ctl_elem_list_sizeof(void);
+
 size_t snd_ctl_event_sizeof(void);
 /** \hideinitializer
  * \brief allocate an invalid #snd_ctl_event_t using standard alloca

include/local.h

@@ -102,6 +102,7 @@
 #define _snd_pcm_status snd_pcm_status
 
 #define _snd_ctl_card_info snd_ctl_card_info
+#define _snd_ctl_card_components snd_ctl_card_components
 #define _snd_ctl_elem_id snd_ctl_elem_id
 #define _snd_ctl_elem_list snd_ctl_elem_list
 #define _snd_ctl_elem_info snd_ctl_elem_info

include/mixer_abst.h

@@ -75,6 +75,7 @@ typedef struct _sm_class_basic {
 	snd_ctl_t *ctl;
 	snd_hctl_t *hctl;
 	snd_ctl_card_info_t *info;
+	snd_ctl_card_components_t *card_components;
 } sm_class_basic_t;
 
 struct sm_elem_ops {

include/sound/uapi/asound.h

@@ -1044,7 +1044,7 @@ struct snd_timer_tread {
  *                                                                          *
  ****************************************************************************/
 
-#define SNDRV_CTL_VERSION		SNDRV_PROTOCOL_VERSION(2, 0, 9)
+#define SNDRV_CTL_VERSION		SNDRV_PROTOCOL_VERSION(2, 0, 10)
 
 struct snd_ctl_card_info {
 	int card;			/* card number */
@@ -1058,6 +1058,18 @@ struct snd_ctl_card_info {
 	unsigned char components[128];	/* card components / fine identification, delimited with one space (AC97 etc..) */
 };
 
+/*
+ * Card components can exceed the fixed 128 bytes in snd_ctl_card_info.
+ * Use SNDRV_CTL_IOCTL_CARD_COMPONENTS to retrieve the full string.
+ */
+#define SNDRV_CTL_COMPONENTS_LEN	512
+
+struct snd_ctl_card_components {
+	int card;			/* card number */
+	unsigned int length;		/* returned length of components string */
+	unsigned char components[SNDRV_CTL_COMPONENTS_LEN];
+};
+
 typedef int __bitwise snd_ctl_elem_type_t;
 #define	SNDRV_CTL_ELEM_TYPE_NONE	((snd_ctl_elem_type_t) 0) /* invalid */
 #define	SNDRV_CTL_ELEM_TYPE_BOOLEAN	((snd_ctl_elem_type_t) 1) /* boolean type */
@@ -1184,6 +1196,7 @@ struct snd_ctl_tlv {
 
 #define SNDRV_CTL_IOCTL_PVERSION	_IOR('U', 0x00, int)
 #define SNDRV_CTL_IOCTL_CARD_INFO	_IOR('U', 0x01, struct snd_ctl_card_info)
+#define SNDRV_CTL_IOCTL_CARD_COMPONENTS	_IOWR('U', 0x02, struct snd_ctl_card_components)
 #define SNDRV_CTL_IOCTL_ELEM_LIST	_IOWR('U', 0x10, struct snd_ctl_elem_list)
 #define SNDRV_CTL_IOCTL_ELEM_INFO	_IOWR('U', 0x11, struct snd_ctl_elem_info)
 #define SNDRV_CTL_IOCTL_ELEM_READ	_IOWR('U', 0x12, struct snd_ctl_elem_value)

src/control/control.c

@@ -388,6 +388,19 @@ int snd_ctl_card_info(snd_ctl_t *ctl, snd_ctl_card_info_t *info)
 	return ctl->ops->card_info(ctl, info);
 }
 
+/**
+ * \brief Get information about the card components.
+ * \param ctl The CTL handle.
+ * \param components The card components information is stored here.
+ * \return 0 on success, otherwise a negative error code.
+ */
+int snd_ctl_card_components(snd_ctl_t *ctl, snd_ctl_card_components_t *components)
+{
+	assert(ctl && components);
+	return ctl->ops->card_components(ctl, components);
+}
+
+
 /**
  * \brief Get a list of element identifiers
  *
@@ -2285,6 +2298,54 @@ const char *snd_ctl_card_info_get_components(const snd_ctl_card_info_t *obj)
 	return (const char *)obj->components;
 }
 
+size_t snd_ctl_card_components_sizeof()
+{
+	return sizeof(snd_ctl_card_components_t);
+}
+
+int snd_ctl_card_components_malloc(snd_ctl_card_components_t **ptr)
+{
+	assert(ptr);
+	*ptr = calloc(1, sizeof(snd_ctl_card_components_t));
+	if (!*ptr)
+		return -ENOMEM;
+	return 0;
+}
+
+void snd_ctl_card_components_free(snd_ctl_card_components_t *obj)
+{
+	free(obj);
+}
+
+void snd_ctl_card_components_clear(snd_ctl_card_components_t *obj)
+{
+	memset(obj, 0, sizeof(snd_ctl_card_components_t));
+}
+
+void snd_ctl_card_components_copy(snd_ctl_card_components_t *dst, const snd_ctl_card_components_t *src)
+{
+	assert(dst && src);
+	*dst = *src;
+}
+
+int snd_ctl_card_components_get_card(const snd_ctl_card_components_t *obj)
+{
+	assert(obj);
+	return obj->card;
+}
+
+unsigned int snd_ctl_card_components_get_length(const snd_ctl_card_components_t *obj)
+{
+	assert(obj);
+	return obj->length;
+}
+
+const char *snd_ctl_card_components_get_string(const snd_ctl_card_components_t *obj)
+{
+	assert(obj);
+	return (const char *)obj->components;
+}
+
 /**
  * \brief get size of #snd_ctl_event_t
  * \return size in bytes

src/control/control_ext.c

@@ -89,6 +89,15 @@ static int snd_ctl_ext_card_info(snd_ctl_t *handle, snd_ctl_card_info_t *info)
 	return 0;
 }
 
+static int snd_ctl_ext_card_components(snd_ctl_t *handle, snd_ctl_card_components_t *components)
+{
+	snd_ctl_ext_t *ext = handle->private_data;
+
+	memset(components, 0, sizeof(*components));
+	components->card = ext->card_idx;
+	return 0;
+}
+
 static int snd_ctl_ext_elem_list(snd_ctl_t *handle, snd_ctl_elem_list_t *list)
 {
 	snd_ctl_ext_t *ext = handle->private_data;
@@ -469,6 +478,7 @@ static const snd_ctl_ops_t snd_ctl_ext_ops = {
 	.async = snd_ctl_ext_async,
 	.subscribe_events = snd_ctl_ext_subscribe_events,
 	.card_info = snd_ctl_ext_card_info,
+	.card_components = snd_ctl_ext_card_components,
 	.element_list = snd_ctl_ext_elem_list,
 	.element_info = snd_ctl_ext_elem_info,
 	.element_add = snd_ctl_ext_elem_add,

src/control/control_hw.c

@@ -136,6 +136,16 @@ static int snd_ctl_hw_card_info(snd_ctl_t *handle, snd_ctl_card_info_t *info)
 	return 0;
 }
 
+static int snd_ctl_hw_card_components(snd_ctl_t *handle, snd_ctl_card_components_t *components)
+{
+	snd_ctl_hw_t *hw = handle->private_data;
+	if (hw->protocol < SNDRV_PROTOCOL_VERSION(2, 0, 10))
+		return -ENXIO;
+	if (ioctl(hw->fd, SNDRV_CTL_IOCTL_CARD_COMPONENTS, components) < 0)
+		return -errno;
+	return 0;
+}
+
 static int snd_ctl_hw_elem_list(snd_ctl_t *handle, snd_ctl_elem_list_t *list)
 {
 	snd_ctl_hw_t *hw = handle->private_data;
@@ -389,6 +399,7 @@ static const snd_ctl_ops_t snd_ctl_hw_ops = {
 	.async = snd_ctl_hw_async,
 	.subscribe_events = snd_ctl_hw_subscribe_events,
 	.card_info = snd_ctl_hw_card_info,
+	.card_components = snd_ctl_hw_card_components,
 	.element_list = snd_ctl_hw_elem_list,
 	.element_info = snd_ctl_hw_elem_info,
 	.element_add = snd_ctl_hw_elem_add,

src/control/control_local.h

@@ -28,6 +28,7 @@ typedef struct _snd_ctl_ops {
 	int (*async)(snd_ctl_t *handle, int sig, pid_t pid);
 	int (*subscribe_events)(snd_ctl_t *handle, int subscribe);
 	int (*card_info)(snd_ctl_t *handle, snd_ctl_card_info_t *info);
+	int (*card_components)(snd_ctl_t *handle, snd_ctl_card_components_t *components);
 	int (*element_list)(snd_ctl_t *handle, snd_ctl_elem_list_t *list);
 	int (*element_info)(snd_ctl_t *handle, snd_ctl_elem_info_t *info);
 	int (*element_add)(snd_ctl_t *handle, snd_ctl_elem_info_t *info);