MLX5DV_GET_CLOCK_INFO(3)

💖 MLX5DV_GET_CLOCK_INFO 💖

okay bestie, gather round, because we're talking about mlx5dv_get_clock_info(3) — a lil' library function from the Library Functions Manual section, and honestly? she's doing the most important job nobody talks about. 🕰️✨

✨ NAME ✨

mlx5dv_get_clock_info — get device clock information 🎀

🌸 SYNOPSIS 🌸

#include <infiniband/mlx5dv.h>

int mlx5dv_get_clock_info(struct ibv_context *ctx_in,
                          struct mlx5dv_clock_info *clock_info);

🦋 DESCRIPTION 🦋

so basically, this function goes and grabs the updated core clock_info straight from the device driver. like, fresh off the press. and why do we care? because later on, you're gonna use that info to translate a completion timestamp from the HCA core clock into nanoseconds. that's the whole glow-up. 💅

now, real talk: the values of the clock get updated from the driver's PTP clock. which means — and this is the part where I need you to lock in — if there is no running PTP client on the machine, then the wall clock conversion will not be accurate. no cap. it's just not gonna be right, and that's not a bug, that's just physics being dramatic. 😭

so here's the move: pass the latest struct mlx5dv_clock_info into mlx5dv_ts_to_ns(3) and that's how you translate the completion timestamp from HCA core clock to nanoseconds. iconic combo, honestly. 🫶

⚠️ and if the clock_info gets too old? the time conversion will return wrong conversion results. periodt. so you, yes you, must make sure that mlx5dv_get_clock_info(3) is called at least once every max_clock_info_update_nsec — that value comes back from the mlx5dv_query_device(3) function. set a lil reminder, bestie, your future self will thank you. ⏰💀

👑 RETURN VALUE 👑

• 0 on success 🎉
• or the value of errno on failure — which is the universe telling you why it went wrong 🙈

🌈 SEE ALSO 🌈

• mlx5dv(7)
• mlx5dv_ts_to_ns(3)

💜 AUTHORS 💜

• Feras Daoud <ferasda@mellanox.com>

and that's the whole page, bestie!! this one's from version 1.0.0 and it's dated 2017-11-08 — so yeah, vintage but still eating. mwah, go keep those clocks updated 🎀💖✨