From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [RFC][PATCH 1/1] net: support for hardware timestamping Date: Tue, 29 Jul 2008 08:54:57 -0700 Message-ID: <20080729085457.033a9fd2@extreme> References: <1217290080-4251-1-git-send-email-opurdila@ixiacom.com> <1217290080-4251-2-git-send-email-opurdila@ixiacom.com> <1217343163.30512.34.camel@ecld0pohly> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Octavian Purdila , netdev@vger.kernel.org To: Patrick Ohly Return-path: Received: from mail.vyatta.com ([216.93.170.194]:38661 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751612AbYG2Py7 (ORCPT ); Tue, 29 Jul 2008 11:54:59 -0400 In-Reply-To: <1217343163.30512.34.camel@ecld0pohly> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 29 Jul 2008 16:52:43 +0200 Patrick Ohly wrote: > On Tue, 2008-07-29 at 03:08 +0300, Octavian Purdila wrote: > > New socket option and socket control message are added as well > > (SO_TIMESTAMPHW and SCM_TIMESTAMPHW). > > How is a network driver notified that it is expected to do hardware time > stamping? The connection between the socket option and the driver isn't > quite clear to me (which might very well be due to my lack of experience > in this area - please bear with me...). Is the driver expected to check > the socket flags whenever it gets a chance? > > IMHO it would be necessary to attach this configuration change not just > to a socket, but also to a message which is then routed to the right > device driver. > In my sky2 sample code, I took a different approach: 1. Why have HW timestamps different than existing timestamps? If you just use existing timestamp, no socket API is needed. 2. Driver can periodically check if socket timestamping is enabled, (atomic_read(&netstamp_needed)) and enable hardware stamping then. Alternatively, add a new notifier to net_enable_timestamp() and net_disable_timestamp().