netdev - Re: [PATCH net v3 2/2] phy: mscc: Fix PTP for VSC8574 and VSC8572

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Message-ID: <aNqKuzlxWwcANiK7@shell.armlinux.org.uk>
Date: Mon, 29 Sep 2025 14:33:47 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Horatiu Vultur <horatiu.vultur@...rochip.com>
Cc: andrew@...n.ch, hkallweit1@...il.com, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	richardcochran@...il.com, vladimir.oltean@....com,
	vadim.fedorenko@...ux.dev, rosenp@...il.com,
	christophe.jaillet@...adoo.fr, steen.hegelund@...rochip.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v3 2/2] phy: mscc: Fix PTP for VSC8574 and VSC8572

On Mon, Sep 29, 2025 at 11:13:02AM +0200, Horatiu Vultur wrote:
> The PTP initialization is two-step. First part are the function
> vsc8584_ptp_probe_once() and vsc8584_ptp_probe() at probe time which
> initialize the locks, queues, creates the PTP device. The second part is
> the function vsc8584_ptp_init() at config_init() time which initialize
> PTP in the HW.

So, to summarise, you register the PTP clock at probe time? At that
point, you get a /dev/ptp* device. Is that device functional without
the config_init() initialisation?

I would hope it is, because one of the fundamental concepts in kernel
programming is... don't publish devices to userspace that are not
completely ready for operation.

Conversely, don't tear down a published device without first
unpublishing it from userspace.

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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