netdev - Re: [PATCH net-next 3/3] ptp: derive the device name from the parent device

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Message-ID: <20120922054345.GA6124@netboy.at.omicron.at>
Date:	Sat, 22 Sep 2012 07:43:46 +0200
From:	Richard Cochran <richardcochran@...il.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	"Keller, Jacob E" <jacob.e.keller@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	John Stultz <john.stultz@...aro.org>,
	"Vick, Matthew" <matthew.vick@...el.com>
Subject: Re: [PATCH net-next 3/3] ptp: derive the device name from the
 parent device

On Fri, Sep 21, 2012 at 08:01:46PM +0100, Ben Hutchings wrote:
> 
> The ethtool command is useful but setting the parent device may be even
> more useful, e.g. you will be able to write udev rules for PHC devices
> based on the parent device's identity.

Thinking about this a bit more, it makes no sense to put the parent
device name into clock_name, because that information is redundant.

  # ls -l /sys/class/ptp/ptp0/
  -r--r--r--    1 root root 8192 Jan  1 00:00 clock_name
  -r--r--r--    1 root root 8192 Jan  1 00:00 dev
  lrwxrwxrwx    1 root root    0 Jan  1 00:00 device -> ../../../fec-1:01

I agree that the parent device is useful, and I will add it. However,
I will leave the clock_name as it is, adding a bit more prose to the
ABI description.

The one case where clock_name becomes really important is when you
have a PHY clock, like in the above example, since it provides a way
to see that the clock is *not* related to the MAC.

Thanks,
Richard
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