netdev - Re: [PATCH v2 net-next 02/14] net: Add a new socket option for a future transmit time.

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Message-ID: <069d42b8-b5d1-cc4f-449c-f5ccbec7fa60@gmail.com>
Date:   Sat, 7 Jul 2018 17:44:30 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Jesus Sanchez-Palencia <jesus.sanchez-palencia@...el.com>,
        netdev@...r.kernel.org
Cc:     tglx@...utronix.de, jan.altenberg@...utronix.de,
        vinicius.gomes@...el.com, kurt.kanzenbach@...utronix.de,
        henrik@...tad.us, richardcochran@...il.com,
        ilias.apalodimas@...aro.org, ivan.khoronzhuk@...aro.org,
        mlichvar@...hat.com, willemb@...gle.com, jhs@...atatu.com,
        xiyou.wangcong@...il.com, jiri@...nulli.us, eric.dumazet@...il.com,
        jeffrey.t.kirsher@...el.com
Subject: Re: [PATCH v2 net-next 02/14] net: Add a new socket option for a
 future transmit time.



On 07/03/2018 03:42 PM, Jesus Sanchez-Palencia wrote:
> From: Richard Cochran <rcochran@...utronix.de>
> 
> This patch introduces SO_TXTIME. User space enables this option in
> order to pass a desired future transmit time in a CMSG when calling
> sendmsg(2). The argument to this socket option is a 8-bytes long struct
> provided by the uapi header net_tstamp.h defined as:
> 
> struct sock_txtime {
> 	clockid_t 	clockid;
> 	u32		flags;
> };
> 
> Note that new fields were added to struct sock by filling a 2-bytes
> hole found in the struct. For that reason, neither the struct size or
> number of cachelines were altered.


> diff --git a/include/uapi/linux/net_tstamp.h b/include/uapi/linux/net_tstamp.h
> index 4fe104b2411f..c9a77c353b98 100644
> --- a/include/uapi/linux/net_tstamp.h
> +++ b/include/uapi/linux/net_tstamp.h
> @@ -141,4 +141,19 @@ struct scm_ts_pktinfo {
>  	__u32 reserved[2];
>  };
>  
> +/*
> + * SO_TXTIME gets a struct sock_txtime with flags being an integer bit
> + * field comprised of these values.
> + */
> +enum txtime_flags {
> +	SOF_TXTIME_DEADLINE_MODE = (1 << 0),
> +
> +	SOF_TXTIME_FLAGS_MASK = (SOF_TXTIME_DEADLINE_MODE)
> +};
> +
> +struct sock_txtime {
> +	clockid_t       clockid;        /* reference clockid */
> +	u32             flags;          /* flags defined by enum txtime_flags */
> +};
> +

I was under the impression that we could not use 'u32' type in include/uapi/linux/* file

This must be replaced by __u32, right ?