netdev - Re: [PATCH 1/3] ptp: Added a brand new class driver for ptp clocks.

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Date:	Tue, 04 May 2010 09:57:54 +0200
From:	Wolfgang Grandegger <wg@...ndegger.com>
To:	Richard Cochran <richardcochran@...il.com>
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH 1/3] ptp: Added a brand new class driver for ptp clocks.

On 05/03/2010 12:07 PM, Richard Cochran wrote:
> On Sun, May 02, 2010 at 12:50:56PM +0200, Wolfgang Grandegger wrote:
>>
>> As long as the device is in use by an application, no other can access
>> it, because the mutex is locked. Other application may want to read the
>> PTP clock time while ptpd is running, though.
> 
> Yes, of course. I implemented it that way just to get started. I first
> want to concentrate on getting the basic drivers in place (still have
> IXP46x and Phyter to do), and then on the ancillary features, like
> timers, time stamping external inputs, and so on.
> 
> I understand that some fine grained access control to the PTP clock
> woul be nice to have, but I am not sure exactly what would work best,
> and I would like to save that decision for later...

OK, fair enough.

> However, if you have some ideas, please take a look at the list of
> features in the docu, and explain how you would like the access
> control to work.

The fine grain locking for set/get properties is tricky. I personally
would just require "CAP_SYS_TIME" for setting properties and a
spin_lock_irq* to protect against concurrent access, just like for
setting/getting system clock properties.

> Or better yet, post a patch ;)

Would do if we could agree on the solution mentioned above.

Wolfgang.

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