[PATCH] Bluetooth: ISO: add timestamp for outgoing HCI ISO packet

[PATCH] Bluetooth: ISO: add timestamp for outgoing HCI ISO packet

[tailu.shi]

The Bluetooth Core Specification defines the 'Time_Stamp' field of
an HCI ISO packet as optional. However, it's mandatory to include
the 'Time_Stamp' field when using HCI ISO packets per section 3.3
'HCI Feature Support Requirement' of TMAP specification.
https://www.bluetooth.com/specifications/specs/html/?src=TMAP_v1.0.1/out/en/index-en.html#UUID-68138fa8-fd1f-1a1b-e552-ddcd8fede9ec

To comply with TMAP, introduce a new socket option BT_PKT_ISO_TIMESTAMP
that allows user application (e.g. PipeWire) to attach timestamp to the
data it sends to the ISO socket within BT_SCM_PKT_ISO_TIMESTAMP CMSG.

When the option is enabled, the kernel extracts the timestamp and copies
it into the 'Time_Stamp' field of the outgoing HCI ISO packet.

This also gives the controller the reference timing information
required for ISO stream synchronization.

A corresponding userspace change is required for full functionality.
A reference implementation is available in PipeWire:
https://gitlab.freedesktop.org/shitailu/pipewire/-/commit/5b3bd74e15febb974c8737a64f31fd17e18cd11b

Signed-off-by: tailu.shi <tailu.shi@samsung.com>
---
 include/net/bluetooth/bluetooth.h |  5 ++++
 include/net/bluetooth/hci_core.h  |  1 +
 net/bluetooth/hci_core.c          |  2 +-
 net/bluetooth/iso.c               | 49 +++++++++++++++++++++++++++----
 4 files changed, 50 insertions(+), 7 deletions(-)

diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
index 69eed69f7f26..f88c83d21c5e 100644
--- a/include/net/bluetooth/bluetooth.h
+++ b/include/net/bluetooth/bluetooth.h
@@ -259,6 +259,10 @@ struct bt_codecs {
 
 #define BT_SCM_PKT_SEQNUM	0x05
 
+#define BT_PKT_ISO_TIMESTAMP     23
+
+#define BT_SCM_PKT_ISO_TIMESTAMP 0x06
+
 __printf(1, 2)
 void bt_info(const char *fmt, ...);
 __printf(1, 2)
@@ -409,6 +413,7 @@ enum {
 	BT_SK_SUSPEND,
 	BT_SK_PKT_STATUS,
 	BT_SK_PKT_SEQNUM,
+	BT_SK_PKT_ISO_TIMESTAMP,
 };
 
 struct bt_sock_list {
diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index a7bffb908c1e..e39d192f8ef6 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -740,6 +740,7 @@ struct hci_conn {
 	struct bt_iso_qos iso_qos;
 	__u8		num_bis;
 	__u8		bis[HCI_MAX_ISO_BIS];
+	bool		iso_pkt_ts;
 
 	unsigned long	flags;
 
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 31308c1de4ec..4264c0229dfb 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -3335,7 +3335,7 @@ static void hci_queue_iso(struct hci_conn *conn, struct sk_buff_head *queue,
 
 	list = skb_shinfo(skb)->frag_list;
 
-	flags = hci_iso_flags_pack(list ? ISO_START : ISO_SINGLE, 0x00);
+	flags = hci_iso_flags_pack(list ? ISO_START : ISO_SINGLE, conn->iso_pkt_ts ? 0x01 : 0x00);
 	hci_add_iso_hdr(skb, conn->handle, flags);
 
 	if (!list) {
diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index be145e2736b7..dd4d198bab4c 100644
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -73,6 +73,9 @@ struct iso_pinfo {
 	__u8			base_len;
 	__u8			base[BASE_MAX_LENGTH];
 	struct iso_conn		*conn;
+	bool			ts_flag;
+	__u32			ts;
+
 };
 
 static struct bt_iso_qos default_qos;
@@ -542,6 +545,7 @@ static int iso_send_frame(struct sock *sk, struct sk_buff *skb,
 	struct iso_conn *conn = iso_pi(sk)->conn;
 	struct bt_iso_qos *qos = iso_sock_get_qos(sk);
 	struct hci_iso_data_hdr *hdr;
+	struct hci_iso_ts_data_hdr *hdr_ts;
 	int len = 0;
 
 	BT_DBG("sk %p len %d", sk, skb->len);
@@ -552,13 +556,20 @@ static int iso_send_frame(struct sock *sk, struct sk_buff *skb,
 	len = skb->len;
 
 	/* Push ISO data header */
-	hdr = skb_push(skb, HCI_ISO_DATA_HDR_SIZE);
-	hdr->sn = cpu_to_le16(conn->tx_sn++);
-	hdr->slen = cpu_to_le16(hci_iso_data_len_pack(len,
-						      HCI_ISO_STATUS_VALID));
+	if (iso_pi(sk)->ts_flag) {
+		hdr_ts = skb_push(skb, HCI_ISO_TS_DATA_HDR_SIZE);
+		hdr_ts->ts = cpu_to_le32(iso_pi(sk)->ts);
+		hdr_ts->sn = cpu_to_le16(conn->tx_sn++);
+		hdr_ts->slen = cpu_to_le16(hci_iso_data_len_pack(len, HCI_ISO_STATUS_VALID));
+	} else {
+		hdr = skb_push(skb, HCI_ISO_DATA_HDR_SIZE);
+		hdr->sn = cpu_to_le16(conn->tx_sn++);
+		hdr->slen = cpu_to_le16(hci_iso_data_len_pack(len, HCI_ISO_STATUS_VALID));
+	}
 
 	if (sk->sk_state == BT_CONNECTED) {
 		hci_setup_tx_timestamp(skb, 1, sockc);
+		conn->hcon->iso_pkt_ts = iso_pi(sk)->ts_flag;
 		hci_send_iso(conn->hcon, skb);
 	} else {
 		len = -ENOTCONN;
@@ -1471,7 +1482,8 @@ static int iso_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 	struct sock *sk = sock->sk;
 	struct sk_buff *skb, **frag;
 	struct sockcm_cookie sockc;
-	size_t mtu;
+	struct cmsghdr *cm;
+	size_t mtu, hlen;
 	int err;
 
 	BT_DBG("sock %p, sk %p", sock, sk);
@@ -1485,10 +1497,23 @@ static int iso_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 
 	hci_sockcm_init(&sockc, sk);
 
+	iso_pi(sk)->ts_flag = false;
 	if (msg->msg_controllen) {
 		err = sock_cmsg_send(sk, msg, &sockc);
 		if (err)
 			return err;
+
+		for (cm = CMSG_FIRSTHDR(msg); cm; cm = CMSG_NXTHDR(msg, cm)) {
+			if (cm->cmsg_level != SOL_BLUETOOTH)
+				continue;
+			if (test_bit(BT_SK_PKT_ISO_TIMESTAMP, &bt_sk(sk)->flags) &&
+			    cm->cmsg_type == BT_SCM_PKT_ISO_TIMESTAMP &&
+			    cm->cmsg_len == CMSG_LEN(sizeof(u32))) {
+				iso_pi(sk)->ts_flag = true;
+				iso_pi(sk)->ts = *(u32 *)CMSG_DATA(cm);
+				break;
+			}
+		}
 	}
 
 	lock_sock(sk);
@@ -1502,7 +1527,8 @@ static int iso_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 
 	release_sock(sk);
 
-	skb = bt_skb_sendmsg(sk, msg, len, mtu, HCI_ISO_DATA_HDR_SIZE, 0);
+	hlen = iso_pi(sk)->ts_flag ? HCI_ISO_TS_DATA_HDR_SIZE : HCI_ISO_DATA_HDR_SIZE;
+	skb = bt_skb_sendmsg(sk, msg, len, mtu, hlen, 0);
 	if (IS_ERR(skb))
 		return PTR_ERR(skb);
 
@@ -1840,6 +1866,17 @@ static int iso_sock_setsockopt(struct socket *sock, int level, int optname,
 
 		break;
 
+	case BT_PKT_ISO_TIMESTAMP:
+		err = copy_safe_from_sockptr(&opt, sizeof(opt), optval, optlen);
+		if (err)
+			break;
+
+		if (opt)
+			set_bit(BT_SK_PKT_ISO_TIMESTAMP, &bt_sk(sk)->flags);
+		else
+			clear_bit(BT_SK_PKT_ISO_TIMESTAMP, &bt_sk(sk)->flags);
+		break;
+
 	default:
 		err = -ENOPROTOOPT;
 		break;
-- 
2.25.1

Re: [PATCH] Bluetooth: ISO: add timestamp for outgoing HCI ISO packet

[Paul Menzel]

Dear Tailu,


Thank you for your patch. A formal request at the beginning to please 
spell your name without the dot/period – maybe: Tailu Shi.

     git config --global user.name "Tailu Shi"
     git commit --amend -s --author="Tailu Shi <tailu.shi@samsung.com>"

Am 11.03.26 um 09:14 schrieb tailu.shi:
> The Bluetooth Core Specification defines the 'Time_Stamp' field of
> an HCI ISO packet as optional. However, it's mandatory to include
> the 'Time_Stamp' field when using HCI ISO packets per section 3.3
> 'HCI Feature Support Requirement' of TMAP specification.
> https://www.bluetooth.com/specifications/specs/html/?src=TMAP_v1.0.1/out/en/index-en.html#UUID-68138fa8-fd1f-1a1b-e552-ddcd8fede9ec
> 
> To comply with TMAP, introduce a new socket option BT_PKT_ISO_TIMESTAMP
> that allows user application (e.g. PipeWire) to attach timestamp to the
> data it sends to the ISO socket within BT_SCM_PKT_ISO_TIMESTAMP CMSG.
> 
> When the option is enabled, the kernel extracts the timestamp and copies
> it into the 'Time_Stamp' field of the outgoing HCI ISO packet.
> 
> This also gives the controller the reference timing information
> required for ISO stream synchronization.
> 
> A corresponding userspace change is required for full functionality.
> A reference implementation is available in PipeWire:
> https://gitlab.freedesktop.org/shitailu/pipewire/-/commit/5b3bd74e15febb974c8737a64f31fd17e18cd11b

Is the timestamp correctly visible in the btmon trace?

> Signed-off-by: tailu.shi <tailu.shi@samsung.com>
> ---
>   include/net/bluetooth/bluetooth.h |  5 ++++
>   include/net/bluetooth/hci_core.h  |  1 +
>   net/bluetooth/hci_core.c          |  2 +-
>   net/bluetooth/iso.c               | 49 +++++++++++++++++++++++++++----
>   4 files changed, 50 insertions(+), 7 deletions(-)
> 
> diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
> index 69eed69f7f26..f88c83d21c5e 100644
> --- a/include/net/bluetooth/bluetooth.h
> +++ b/include/net/bluetooth/bluetooth.h
> @@ -259,6 +259,10 @@ struct bt_codecs {
>   
>   #define BT_SCM_PKT_SEQNUM	0x05
>   
> +#define BT_PKT_ISO_TIMESTAMP     23
> +
> +#define BT_SCM_PKT_ISO_TIMESTAMP 0x06
> +
>   __printf(1, 2)
>   void bt_info(const char *fmt, ...);
>   __printf(1, 2)
> @@ -409,6 +413,7 @@ enum {
>   	BT_SK_SUSPEND,
>   	BT_SK_PKT_STATUS,
>   	BT_SK_PKT_SEQNUM,
> +	BT_SK_PKT_ISO_TIMESTAMP,
>   };
>   
>   struct bt_sock_list {
> diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
> index a7bffb908c1e..e39d192f8ef6 100644
> --- a/include/net/bluetooth/hci_core.h
> +++ b/include/net/bluetooth/hci_core.h
> @@ -740,6 +740,7 @@ struct hci_conn {
>   	struct bt_iso_qos iso_qos;
>   	__u8		num_bis;
>   	__u8		bis[HCI_MAX_ISO_BIS];
> +	bool		iso_pkt_ts;
>   
>   	unsigned long	flags;
>   
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index 31308c1de4ec..4264c0229dfb 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -3335,7 +3335,7 @@ static void hci_queue_iso(struct hci_conn *conn, struct sk_buff_head *queue,
>   
>   	list = skb_shinfo(skb)->frag_list;
>   
> -	flags = hci_iso_flags_pack(list ? ISO_START : ISO_SINGLE, 0x00);
> +	flags = hci_iso_flags_pack(list ? ISO_START : ISO_SINGLE, conn->iso_pkt_ts ? 0x01 : 0x00);
>   	hci_add_iso_hdr(skb, conn->handle, flags);
>   
>   	if (!list) {
> diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
> index be145e2736b7..dd4d198bab4c 100644
> --- a/net/bluetooth/iso.c
> +++ b/net/bluetooth/iso.c
> @@ -73,6 +73,9 @@ struct iso_pinfo {
>   	__u8			base_len;
>   	__u8			base[BASE_MAX_LENGTH];
>   	struct iso_conn		*conn;
> +	bool			ts_flag;
> +	__u32			ts;
> +
>   };
>   
>   static struct bt_iso_qos default_qos;
> @@ -542,6 +545,7 @@ static int iso_send_frame(struct sock *sk, struct sk_buff *skb,
>   	struct iso_conn *conn = iso_pi(sk)->conn;
>   	struct bt_iso_qos *qos = iso_sock_get_qos(sk);
>   	struct hci_iso_data_hdr *hdr;
> +	struct hci_iso_ts_data_hdr *hdr_ts;
>   	int len = 0;
>   
>   	BT_DBG("sk %p len %d", sk, skb->len);
> @@ -552,13 +556,20 @@ static int iso_send_frame(struct sock *sk, struct sk_buff *skb,
>   	len = skb->len;
>   
>   	/* Push ISO data header */
> -	hdr = skb_push(skb, HCI_ISO_DATA_HDR_SIZE);
> -	hdr->sn = cpu_to_le16(conn->tx_sn++);
> -	hdr->slen = cpu_to_le16(hci_iso_data_len_pack(len,
> -						      HCI_ISO_STATUS_VALID));
> +	if (iso_pi(sk)->ts_flag) {
> +		hdr_ts = skb_push(skb, HCI_ISO_TS_DATA_HDR_SIZE);
> +		hdr_ts->ts = cpu_to_le32(iso_pi(sk)->ts);
> +		hdr_ts->sn = cpu_to_le16(conn->tx_sn++);
> +		hdr_ts->slen = cpu_to_le16(hci_iso_data_len_pack(len, HCI_ISO_STATUS_VALID));
> +	} else {
> +		hdr = skb_push(skb, HCI_ISO_DATA_HDR_SIZE);
> +		hdr->sn = cpu_to_le16(conn->tx_sn++);
> +		hdr->slen = cpu_to_le16(hci_iso_data_len_pack(len, HCI_ISO_STATUS_VALID));
> +	}
>   
>   	if (sk->sk_state == BT_CONNECTED) {
>   		hci_setup_tx_timestamp(skb, 1, sockc);
> +		conn->hcon->iso_pkt_ts = iso_pi(sk)->ts_flag;
>   		hci_send_iso(conn->hcon, skb);
>   	} else {
>   		len = -ENOTCONN;
> @@ -1471,7 +1482,8 @@ static int iso_sock_sendmsg(struct socket *sock, struct msghdr *msg,
>   	struct sock *sk = sock->sk;
>   	struct sk_buff *skb, **frag;
>   	struct sockcm_cookie sockc;
> -	size_t mtu;
> +	struct cmsghdr *cm;
> +	size_t mtu, hlen;
>   	int err;
>   
>   	BT_DBG("sock %p, sk %p", sock, sk);
> @@ -1485,10 +1497,23 @@ static int iso_sock_sendmsg(struct socket *sock, struct msghdr *msg,
>   
>   	hci_sockcm_init(&sockc, sk);
>   
> +	iso_pi(sk)->ts_flag = false;
>   	if (msg->msg_controllen) {
>   		err = sock_cmsg_send(sk, msg, &sockc);
>   		if (err)
>   			return err;
> +
> +		for (cm = CMSG_FIRSTHDR(msg); cm; cm = CMSG_NXTHDR(msg, cm)) {
> +			if (cm->cmsg_level != SOL_BLUETOOTH)
> +				continue;
> +			if (test_bit(BT_SK_PKT_ISO_TIMESTAMP, &bt_sk(sk)->flags) &&
> +			    cm->cmsg_type == BT_SCM_PKT_ISO_TIMESTAMP &&
> +			    cm->cmsg_len == CMSG_LEN(sizeof(u32))) {
> +				iso_pi(sk)->ts_flag = true;
> +				iso_pi(sk)->ts = *(u32 *)CMSG_DATA(cm);
> +				break;
> +			}
> +		}
>   	}
>   
>   	lock_sock(sk);
> @@ -1502,7 +1527,8 @@ static int iso_sock_sendmsg(struct socket *sock, struct msghdr *msg,
>   
>   	release_sock(sk);
>   
> -	skb = bt_skb_sendmsg(sk, msg, len, mtu, HCI_ISO_DATA_HDR_SIZE, 0);
> +	hlen = iso_pi(sk)->ts_flag ? HCI_ISO_TS_DATA_HDR_SIZE : HCI_ISO_DATA_HDR_SIZE;
> +	skb = bt_skb_sendmsg(sk, msg, len, mtu, hlen, 0);
>   	if (IS_ERR(skb))
>   		return PTR_ERR(skb);
>   
> @@ -1840,6 +1866,17 @@ static int iso_sock_setsockopt(struct socket *sock, int level, int optname,
>   
>   		break;
>   
> +	case BT_PKT_ISO_TIMESTAMP:
> +		err = copy_safe_from_sockptr(&opt, sizeof(opt), optval, optlen);
> +		if (err)
> +			break;
> +
> +		if (opt)
> +			set_bit(BT_SK_PKT_ISO_TIMESTAMP, &bt_sk(sk)->flags);
> +		else
> +			clear_bit(BT_SK_PKT_ISO_TIMESTAMP, &bt_sk(sk)->flags);
> +		break;
> +
>   	default:
>   		err = -ENOPROTOOPT;
>   		break;

The diff looks good.

Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>


Kind regards,

Paul

Re: [PATCH] Bluetooth: ISO: add timestamp for outgoing HCI ISO packet

[Tailu Shi]

Hi Paul,

Thank you for the review and the helpful suggestion about my name.

I have updated my Git configuration and amended the commit as you advised:

    git config --global user.name "Tailu Shi"
    git commit --amend -s --author="Tailu Shi <tailu.shi@samsung.com>"


On Wed, 11 Mar 2026 09:54:38 +0100 Paul Menzel wrote:
>> A corresponding userspace change is required for full functionality.
>> A reference implementation is available in PipeWire:
>> https://gitlab.freedesktop.org/shitailu/pipewire/-/commit/5b3bd74e15febb974c8737a64f31fd17e18cd11b
> 
> Is the timestamp correctly visible in the btmon trace?

Yes, it can be seen in the btmon trace. The test was performed on the
kernel 7.0.0‑rc1+, using BlueZ 5.85 and PipeWire 1.5.84 with the
'bluez5.iso-tx-timestamp' configuration option enabled.

But seems the btmon v5.85 and v5.86 fails to parse it directly with
the command. However, the 'ts' field can be seen clearly with Wireshark.

The things are like below:

1) btmon v5.86
 $ btmon -r dump.btsnoop -I |grep -A1 'ISO Data TX: Handle 2563'
 < ISO Data TX: Handle 2563 [5/18] SN 2                 #10999 [hci0] 128.571172
         02 00 3c 00 00 00 00 00 00 00 00 00 00 00 00 00  ..<.............
 --

2) Wireshark
 Frame 19604: 72 bytes on wire (576 bits), 72 bytes captured (576 bits)
 Bluetooth
 Bluetooth Linux Monitor Transport
 Bluetooth HCI ISO Packet
     .... 1010 0000 0011 = Connection Handle: 0xa03
     ..10 .... .... .... = PB Flag: Complete SDU (0x2)
     .1.. .... .... .... = Timestamp present: True
     0... .... .... .... = Reserved: 0x0
     ..00 0000 0100 0100 = Data Length: 68
     Data
     [Connect in frame: 18836]
 Bluetooth ISO Data
     Timestamp: 805103660µs
     Sequence Number: 84
     .... 0000 0011 1100 = SDU Length: 60
     SDU

Raw data:
 0000   03 6a 44 00 2c e8 fc 2f 54 00 3c 00 00 00 00 00   .jD.,../T.<.....
 0010   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
 0020   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
 0030   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
 0040   38 24 f9 4a 0d 00 00 03                           8$.J....


Thanks for your time again!

Best regards,

Tailu Shi

Re: [PATCH] Bluetooth: ISO: add timestamp for outgoing HCI ISO packet

[Tailu Shi]

Hi Pauli,

Thanks for the detailed review and for sharing your RFC patches.

On Wed, 11 Mar 2026 18:24:23 +0200 Pauli Virtanen wrote:
> These timestamps are in controller clock domain, so generic host like
> Linux appears to need to perform clock synchronization via
> HCI_OP_LE_READ_ISO_TX_SYNC to be able to provide timestamps.

I agree that, according to Core v6.2 Vol 6 Part G Section 3, the timestamp
must be derived from the Controller's clock. However, Section 3.3 also defines
a falllback where the controller decides the CIS/BIS event when the
host‑supplied timestamp is not based on the Controller's clock. It looks
contradictory.

Section 3.3 further states that the host may retrieve the timestamp via
HCI_LE_Read_ISO_TX_Sync command. The wording makes it optional. And also
as you have noted, many controller returns 0 for it, leaving the practical
challenges to make it work properly.

That's why we considered leaving it to the userspace application.

> I had in the works a not fully finished patch series adding the same
> thing + LE Read ISO TX Sync + tests. I sent these now to the list in
> their current state, maybe they are useful if you are working on this
>
> https://lore.kernel.org/linux-bluetooth/cover.1773245666.git.pav@iki.fi/T/
> 
> https://lore.kernel.org/linux-bluetooth/cover.1773245672.git.pav@iki.fi/T/
> 
> The tests pass, but not really tested to satisfaction on real
> controllers.
> 
> From what I saw, it seems several controllers like Intel AX210 and some
> Realtek ones don't implement LE Read ISO TX Sync correctly (returns 0
> timestamp), so in those cases it AFAICS it's not possible to provide
> host timestamps.
> 
> Getting the clock sync via LE Read ISO TX Sync to work properly across
> controllers is maybe not so easy, as it appears the Core Specification
> is somewhat unclear how it should work.

I have reviewed the series you posted and I think it both complete and
elegant. Since my earlier work is now covered by your commit (08692f3...),
I will withdraw my patch.

I've cherry-picked your series and kept the PipeWire logic that passes the
timestamp via BT_SCM_PKT_ISO_TIMESTAMP CMSG. The implementation works on my
platform (based on the Kernel 7.0.0-rc1, BlueZ 5.85 and PipeWire 1.5.84).
The timestamp can be observed in the btmon trace.

Partial HCI parsed by Wireshark:
 Frame 32436: 72 bytes on wire (576 bits), 72 bytes captured (576 bits)
 Bluetooth
 Bluetooth Linux Monitor Transport
 Bluetooth HCI ISO Packet
     .... 1010 0000 0101 = Connection Handle: 0xa05
     ..10 .... .... .... = PB Flag: Complete SDU (0x2)
     .1.. .... .... .... = Timestamp present: True
     0... .... .... .... = Reserved: 0x0
     ..00 0000 0100 0100 = Data Length: 68
     Data
     [Connect in frame: 9436]
 Bluetooth ISO Data
     Timestamp: 469412333us
     Sequence Number: 3595
     .... 0000 0011 1100 = SDU Length: 60
     SDU

Please feel free to add the following Tested-by line if it helps:
Tested-by: Tailu Shi <tailu.shi@samsung.com>

May I know if you have any plan to merge this series? And also please feel
free to let me know if there's anything I can help to move this forward.

> This sends timestamps in host clock domain and has no clock sync, but I
> guess this is just for testing.

I think it's better to have a complete implementation solution. So if possible,
I would like to improve it and push it forward. Please feel free to let me
know if you have any other opinions.

> I think these are not needed, they can be passed as arguments to
> iso_send_frame().
> 
> Adding them to iso_pinfo() probably causes a data race if two processes
> sendmsg() at the same time.

Thank you for identifying this potential data race issue. It was not considered
in the current patch, and I will incorporate your suggestion in future development.

> I would put this in a separate function.

Agreed. It will make code clear. I will keep this code style in future development.


Thank you again for the detailed review!

Best regards!

Tailu