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] link to v3

Signed-off-by: Maciej Strozek <mstrozek@opensource.cirrus.com>

Author: mstrozek

include/local.h

@@ -101,7 +101,6 @@
 #define _snd_pcm_sw_params snd_pcm_sw_params
 #define _snd_pcm_status snd_pcm_status
 
-#define _snd_ctl_card_info snd_ctl_card_info
 #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
@@ -226,6 +225,20 @@
 #include "seq_midi_event.h"
 #include "list.h"
 
+/* V2 structure - increased components string from 128 bytes to 512 bytes */
+struct _snd_ctl_card_info {
+       int card;                       /* card number */
+       int pad;                        /* reserved for future (was type) */
+       unsigned char id[16];           /* ID of card (user selectable) */
+       unsigned char driver[16];       /* Driver name */
+       unsigned char name[32];         /* Short name of soundcard */
+       unsigned char longname[80];     /* name + info text about soundcard */
+       unsigned char reserved_[16];    /* reserved for future (was ID of mixer) */
+       unsigned char mixername[80];    /* visual mixer identification */
+       unsigned char components[512];  /* card components / fine identification, delimited with one space (AC97 etc..) */
+};
+
+
 struct _snd_async_handler {
 	enum {
 		SND_ASYNC_HANDLER_GENERIC,

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 +1058,16 @@ 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.
+ */
+struct snd_ctl_card_components {
+	int card;			/* card number */
+	unsigned int length;		/* returned length of components string for ioctl query */
+	unsigned char components[512];	/* card components / fine identification, delimited with one space (AC97 etc..) */
+};
+
 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 +1194,7 @@ 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_hw.c

@@ -129,10 +129,45 @@ static int snd_ctl_hw_subscribe_events(snd_ctl_t *handle, int subscribe)
 static int snd_ctl_hw_card_info(snd_ctl_t *handle, snd_ctl_card_info_t *info)
 {
 	snd_ctl_hw_t *hw = handle->private_data;
-	if (ioctl(hw->fd, SNDRV_CTL_IOCTL_CARD_INFO, info) < 0) {
+	struct snd_ctl_card_info kinfo;
+	struct snd_ctl_card_components comp;
+
+	if (ioctl(hw->fd, SNDRV_CTL_IOCTL_CARD_INFO, &kinfo) < 0) {
 		snd_errornum(CONTROL, "SNDRV_CTL_IOCTL_CARD_INFO failed");
 		return -errno;
 	}
+
+	snd_ctl_card_info_clear(info);
+	info->card = kinfo.card;
+	info->pad = kinfo.pad;
+	memcpy(info->id, kinfo.id, sizeof(kinfo.id));
+	memcpy(info->driver, kinfo.driver, sizeof(kinfo.driver));
+	memcpy(info->name, kinfo.name, sizeof(kinfo.name));
+	memcpy(info->longname, kinfo.longname, sizeof(kinfo.longname));
+	memcpy(info->reserved_, kinfo.reserved_, sizeof(kinfo.reserved_));
+	memcpy(info->mixername, kinfo.mixername, sizeof(kinfo.mixername));
+	if (strnlen((char *)kinfo.components, sizeof(kinfo.components)) > 0 &&
+	    kinfo.components[sizeof(kinfo.components) - 2] == '>') {
+		memset(&comp, 0, sizeof(comp));
+		if (ioctl(hw->fd, SNDRV_CTL_IOCTL_CARD_COMPONENTS, &comp) < 0) {
+			snd_errornum(CONTROL, "SNDRV_CTL_IOCTL_CARD_COMPONENTS query failed");
+			return -errno;
+		}
+		if (comp.length == 0 || comp.length > sizeof(comp.components)) {
+			snd_errornum(CONTROL, "SNDRV_CTL_IOCTL_CARD_COMPONENTS unexpected length %u",
+				     comp.length);
+			return -errno;
+		}
+		comp.length = sizeof(comp.components);
+		if (ioctl(hw->fd, SNDRV_CTL_IOCTL_CARD_COMPONENTS, &comp) < 0) {
+			snd_errornum(CONTROL, "SNDRV_CTL_IOCTL_CARD_COMPONENTS read failed");
+			return -errno;
+		}
+		memcpy(info->components, comp.components, sizeof(info->components));
+	} else {
+		memcpy(info->components, kinfo.components, sizeof(info->components));
+	}
+
 	return 0;
 }