linux-kernel - Re: [PATCH v2] Bluetooth: ISO: Support SOCK

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Message-ID: <d6906cfb7fae090b9fe0c1c5b8708182eb939b42.camel@iki.fi>
Date: Wed, 02 Jul 2025 18:22:56 +0300
From: Pauli Virtanen <pav@....fi>
To: yang.li@...ogic.com, Marcel Holtmann <marcel@...tmann.org>, Johan
 Hedberg	 <johan.hedberg@...il.com>, Luiz Augusto von Dentz
 <luiz.dentz@...il.com>,  "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo
 Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>
Cc: linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Bluetooth: ISO: Support SOCK_RCVTSTAMP via CMSG for
 ISO sockets

Hi,

ke, 2025-07-02 kello 19:35 +0800, Yang Li via B4 Relay kirjoitti:
> From: Yang Li <yang.li@...ogic.com>
> 
> User-space applications (e.g., PipeWire) depend on
> ISO-formatted timestamps for precise audio sync.
> 
> Signed-off-by: Yang Li <yang.li@...ogic.com>
> ---
> Changes in v2:
> - Support SOCK_RCVTSTAMPNS via CMSG for ISO sockets
> - Link to v1: https://lore.kernel.org/r/20250429-iso_ts-v1-1-e586f30de6cb@amlogic.com
> ---
>  net/bluetooth/iso.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
> index fc22782cbeeb..6927c593a1d6 100644
> --- a/net/bluetooth/iso.c
> +++ b/net/bluetooth/iso.c
> @@ -2308,6 +2308,9 @@ void iso_recv(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
>  				goto drop;
>  			}
>  
> +			/* Record the timestamp to skb*/
> +			skb->skb_mstamp_ns = le32_to_cpu(hdr->ts);

Hardware timestamps are supposed to go in

	skb_hwtstamps(skb)->hwtstamp

See Documentation/networking/timestamping.rst
"3.1 Hardware Timestamping Implementation: Device Drivers" and how it
is done in drivers/net/

This documentation also explains how user applications can obtain the
hardware timestamps.

AFAIK, skb->tstamp (skb->skb_mstamp_ns is union for it) must be in
system clock. The hdr->ts is in some unsynchronized controller clock,
so they should go to HW timestamps.

> +
>  			len = __le16_to_cpu(hdr->slen);
>  		} else {
>  			struct hci_iso_data_hdr *hdr;
> 
> ---
> base-commit: 3bc46213b81278f3a9df0324768e152de71eb9fe
> change-id: 20250421-iso_ts-c82a300ae784
> 
> Best regards,

-- 
Pauli Virtanen