netdev - Re: [PATCH net-next v4] ptp: add Alibaba CIPU PTP clock driver

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Message-ID: <20250815113814.5e135318@kernel.org>
Date: Fri, 15 Aug 2025 11:38:14 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Wen Gu <guwen@...ux.alibaba.com>
Cc: richardcochran@...il.com, andrew+netdev@...n.ch, davem@...emloft.net,
 edumazet@...gle.com, pabeni@...hat.com, xuanzhuo@...ux.alibaba.com,
 dust.li@...ux.alibaba.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, David
 Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH net-next v4] ptp: add Alibaba CIPU PTP clock driver

On Tue, 12 Aug 2025 19:53:21 +0800 Wen Gu wrote:
> This adds a driver for Alibaba CIPU PTP clock. The CIPU, an underlying
> infrastructure of Alibaba Cloud, synchronizes time with reference clocks
> continuously and provides PTP clocks for VMs and bare metals in cloud.

> +static struct attribute *ptp_cipu_attrs[] = {
> +	&dev_attr_reg_dev_feat.attr,
> +	&dev_attr_reg_gst_feat.attr,
> +	&dev_attr_reg_drv_ver.attr,
> +	&dev_attr_reg_env_ver.attr,
> +	&dev_attr_reg_dev_stat.attr,
> +	&dev_attr_reg_sync_stat.attr,
> +	&dev_attr_reg_tm_prec_ns.attr,
> +	&dev_attr_reg_epo_base_yr.attr,
> +	&dev_attr_reg_leap_sec.attr,
> +	&dev_attr_reg_max_lat_ns.attr,
> +	&dev_attr_reg_mt_tout_us.attr,
> +	&dev_attr_reg_thresh_us.attr,
> +
> +	&dev_attr_ptp_gettm.attr,
> +	&dev_attr_ptp_gettm_inval_err.attr,
> +	&dev_attr_ptp_gettm_tout_err.attr,
> +	&dev_attr_ptp_gettm_excd_thresh.attr,
> +
> +	&dev_attr_dev_clk_abn.attr,
> +	&dev_attr_dev_clk_abn_rec.attr,
> +	&dev_attr_dev_maint.attr,
> +	&dev_attr_dev_maint_rec.attr,
> +	&dev_attr_dev_maint_tout.attr,
> +	&dev_attr_dev_busy.attr,
> +	&dev_attr_dev_busy_rec.attr,
> +	&dev_attr_dev_err.attr,
> +	&dev_attr_dev_err_rec.attr,

This driver is lacking documentation. You need to describe how the user
is expected to interact with the device and document all these sysfs
attributes.

Maybe it's just me, but in general I really wish someone stepped up
and created a separate subsystem for all these cloud / vm clocks.
They have nothing to do with PTP. In my mind PTP clocks are simple HW
tickers on which we build all the time related stuff. While this driver
reports the base year for the epoch and leap second status via sysfs.