Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755562AbXJAQDe (ORCPT ); Mon, 1 Oct 2007 12:03:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752057AbXJAQD0 (ORCPT ); Mon, 1 Oct 2007 12:03:26 -0400 Received: from ug-out-1314.google.com ([66.249.92.169]:54439 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751703AbXJAQDZ (ORCPT ); Mon, 1 Oct 2007 12:03:25 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; b=fo7h9qH3702kCGRoBxzmu5kUKaFhESTjQwfa4FK+CsoEh1cXgEaGuDseXhU7AVezczB/DNzGazntT9mta9+bc86PYdHjCqwU5ifnqJFofbgF5f2ppfcv3lJ7LqLjlRAskIzkx0PqQwf/yAwDn28BTXiuLGbt4Slex3tD5rM51pA= Message-ID: <59ad55d30710010903y76330624ka45747c0b5983cfd@mail.gmail.com> Date: Mon, 1 Oct 2007 12:03:23 -0400 From: "=?UTF-8?Q?Kristian_H=C3=B8gsberg?=" To: "Pieter Palmers" Subject: Re: [PATCH] firewire: adopt read cycle timer ABI from raw1394 Cc: "Stefan Richter" , "=?UTF-8?Q?Kristian_H=C3=B8gsberg?=" , linux1394-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org In-Reply-To: <4700BE87.2040107@joow.be> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <4700BE87.2040107@joow.be> X-Google-Sender-Auth: 6fb7f3c2a53faea2 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2525 Lines: 61 On 10/1/07, Pieter Palmers wrote: > Stefan Richter wrote: > >> This duplicates the read cycle timer feature of raw1394 (added in Linux > >> 2.6.21) in firewire-core's userspace ABI. > > > > Kristian and Pieter, does this simple duplication of the ioctl make > > sense on its own? AFAIU rawiso's iso packet buffers look different from > > fw-cdevs's. It seems to me as if rawiso always put the cycle into a user > > buffer for each iso packet received... > > > > raw1394.h::struct raw1394_iso_packet_info { > > __u32 offset; > > __u16 len; > > __u16 cycle; /* recv only */ > > __u8 channel; /* recv only */ > > __u8 tag; > > __u8 sy; > > }; > > > > raw1394.c::raw1394_iso_recv_packets() > > > > /* copy the packet_infos out */ > > for (i = 0; i < upackets.n_packets; i++) { > > if (__copy_to_user(&upackets.infos[i], > > &fi->iso_handle->infos[packet], > > sizeof(struct raw1394_iso_packet_info))) > > return -EFAULT; > > > > packet = (packet + 1) % fi->iso_handle->buf_packets; > > } > > > > ...while the Juju ABI returns the cycle only for those packets whose > > fw_cdev_iso_packet.control had the FW_CDEV_ISO_INTERRUPT flag set. > > The cycle is then written out in the fw_cdev_event_iso_interrupt event > > which happens when this particular packet was received. Right? > > > > Pieter, do applications like yours need the cycle counter only for a few > > predetermined packets or for each and every packet? > > We need it for every packet for two reasons: > 1) it's the only way to determine how many packets were dropped when > packet drops are flagged in the callback Your application should know what the timestamp should be for each iso receive callback and if you see a larger value than expected you can use that to calculate how many cycles were lost. > 2) we convert the 16-bit SYT timestamp of a packet to a full 32-bit > cycle counter value. This because the range of the 16-bit SYT is too > small (only 16 packets) for systems that have large buffering. If you get the timestamp for the first packet in a receive batch, you can still do this, right? cheers, Kristian - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/