linux-kernel - getting a PHC reference in a kernel module?

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Date:   Mon, 17 Sep 2018 17:09:30 +0000
From:   "Spruyt, Randy" <Randy.Spruyt@...istiedigital.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "john.stultz@...aro.org" <john.stultz@...aro.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "sboyd@...eaurora.org" <sboyd@...eaurora.org>
Subject: getting a PHC reference in a kernel module?

I'm new to kernel driver development, so I hope you bear with me on the question. 

I'd like to timestamp an IRQ event in a kernel module using a PTP synchronized clock (e.g. the PHC from eth0 = /dev/ptp0). E.g. a GPIO pin goes high, I'd like to keep track of when this happened as accurate as we can. One option is to use getnstimeofday() and have phc2sys synchronize /dev/ptp0 with the system  clock. 

This seems to work but I feel like there is a more direct way to just query the PHC clock e.g. using struct ptp_clock* and gettime64(). The question is how to get this pointer, find_driver()? Or something else? Perhaps this is not exposed for a reason?

If this is the wrong way to go about this, by all means, I'm open to suggestions.