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From: Stefan Richter <stefanr@s5r6.in-berlin.de>
To: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Cc: tiwai@suse.de, alsa-devel@alsa-project.org, clemens@ladisch.de,
	ffado-devel@lists.sf.net
Subject: Re: [PATCH 18/39] firewire-lib: Add a fallback at RCODE_CANCELLED
Date: Sat, 1 Mar 2014 15:20:50 +0100
Message-ID: <20140301152050.5de701a3@stein> (raw)
In-Reply-To: <5311D0FC.7020302@sakamocchi.jp>

On Mar 01 Takashi Sakamoto wrote:
[...]
>> I wonder:  Now that firewire-lib's use cases are expanded far
>> beyond LaCie Speakers and Griffin FireWave, do we need to implement
>> deferred transactions in firewire-lib too?
> 
> Yes. I confirmed some devices use deffered transaction for AV/C 
> CONTROL request.
> But I still pending this issue, because of the way to handle the 
> 'unspecified interval'.

Are these devices already supported or reported to work with FFADO?
If yes, then the interval is probably typically less than FFADO's built-in
FCP transaction timeout, i.e. 200 (or 400?) ms.

> I plan to solve this issue for my future work.

OK.

>> A related question:  Since FFADO applies 200 ms or more as FCP
>> transaction timeout, shouldn't firewire-lib's fcp.c increase
>> FCP_TIMEOUT_MS from 125 to 200 or more as well?
> 
> For this developing, I've spent much time with my test devices.
> But I've never experienced disadvantages under FCP_TIMEOUT_MS=125msec.
> So feel no importance.
> 
> If you feel this importance, please post your patch with proper reasons.

This is mostly a question to the ffado-devel subscribers.  125 ms is of
course enough for devices which comply with the specification in this
regard.  The question is whether FFADO developers know of devices (or
suspect devices) which exceed the standard 100 ms and need more like 200
ms.

In any case, this question is unrelated to your patch (apart from the
unlikely worst-case timeout which you noted in the changelog).

>> This is about case b) and, now that I think about it, also about case
>> a) in my list further above.
> 
> The case a) is for ctype=reserved. Current ALSA Firewire drivers don't 
> utilize it.
> So I have never considered about this case.

Of course; the kernel is never going to emit a reserved ctype.  And
if malicious or faulty userspace does, the specified target behavior is
exactly the desired behavior.

> For the case b), I'm optimistic because current fcp_avc_transaction() 
> don't return till the first AV/C response comes (or AV/C request is
> error). This means that the driver basically don't send any AV/C
> transaction at the same time.
> 
> Furthermore, my drivers basically generate some AV/C transaction in
> driver's probe/remove state or starting/stopping playback/capture of
> PCM samples/MIDI messages. So I believe that FFADO/ALSA rarely transfer
> some AV/C transactions at the same time.
> 
> In these reasons, I'm optimistic for device's ignorance of AV/C request.

>From what I understood so far, I agree.  (And besides, the specified
behavior of ignoring the command and not sending a response is of course
better than, for example, execution of a command but failure to send
the response.)
-- 
Stefan Richter
-=====-====- --== ----=
http://arcgraph.de/sr/

  reply index

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-28  3:27 [GIT PULL][PATCH 00/39] Enhancement of support for Firewire devices Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 01/39] firewire-lib: Rename functions, structure, member for AMDTP Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 02/39] firewire-lib: Add macros instead of fixed value " Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 03/39] firewire-lib: Add 'direction' member to 'amdtp_stream' structure Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 04/39] firewire-lib: Split some codes into functions to reuse for both streams Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 05/39] firewire-lib: Add support for AMDTP in-stream and PCM capture Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 06/39] firewire-lib: Add support for MIDI capture/playback Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 07/39] firewire-lib: Give syt value as parameter to handle_out_packet() Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 08/39] firewire-lib: Add support for duplex streams synchronization in blocking mode Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 09/39] firewire-lib: Add sort function for transmitted packet Takashi Sakamoto
2014-02-28  6:40   ` Takashi Iwai
2014-02-28 14:31     ` Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 10/39] firewire-lib: Add transfer delay to synchronized duplex streams Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 11/39] firewire-lib: Add support for channel mapping Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 12/39] firewire-lib: Rename macros, variables and functions for CMP Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 13/39] firewire-lib: Add 'direction' member to 'cmp_connection' structure Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 14/39] firewire-lib: Add handling output connection by CMP Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 15/39] firewire-lib: Add a new function to check others' connection Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 16/39] firewire-lib: Add some AV/C general commands Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 17/39] firewire-lib: Add quirks for Fireworks Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 18/39] firewire-lib: Add a fallback at RCODE_CANCELLED Takashi Sakamoto
2014-02-28 20:25   ` Stefan Richter
2014-02-28 20:39     ` Stefan Richter
2014-03-01  3:18     ` Takashi Sakamoto
2014-03-01 10:10       ` Stefan Richter
2014-03-01 12:22         ` Takashi Sakamoto
2014-03-01 14:20           ` Stefan Richter [this message]
2014-03-04  1:35             ` [FFADO-devel] " Jonathan Woithe
2014-03-04  8:33               ` Stefan Richter
2014-03-04  9:28                 ` Stefan Richter
2014-03-01 10:34   ` Stefan Richter
2014-03-01 12:23     ` Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 19/39] fireworks: Add skelton for Fireworks based devices Takashi Sakamoto
2014-02-28  6:51   ` Takashi Iwai
2014-02-28 15:05     ` Takashi Sakamoto
2014-02-28 15:10       ` Takashi Iwai
2014-02-28 15:36         ` Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 20/39] fireworks: Add transaction and some commands Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 21/39] fireworks: Add connection and stream management Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 22/39] fireworks: Add proc interface for debugging purpose Takashi Sakamoto
2014-02-28  6:54   ` Takashi Iwai
2014-03-01 13:17     ` Takashi Sakamoto
2014-03-03  9:01       ` Takashi Iwai
2014-03-04 14:10         ` Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 23/39] fireworks: Add MIDI interface Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 24/39] fireworks: Add PCM interface Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 25/39] fireworks: Add hwdep interface Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 26/39] fireworks: Add command/response functionality into " Takashi Sakamoto
2014-02-28  6:58   ` Takashi Iwai
2014-03-01 13:18     ` Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 27/39] bebob: Add skelton for BeBoB based devices Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 28/39] bebob: Add commands and connections/streams management Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 29/39] bebob: Add proc interface for debugging purpose Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 30/39] bebob: Add MIDI interface Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 31/39] bebob: Add PCM interface Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 32/39] bebob: Add hwdep interface Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 33/39] bebob: Prepare for device specific operations Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 34/39] bebob: Add support for Terratec PHASE, EWS series and Aureon Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 35/39] bebob: Add support for Yamaha GO series Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 36/39] bebob: Add support for Focusrite Saffire/SaffirePro series Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 37/39] bebob: Add support for M-Audio usual Firewire series Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 38/39] bebob: Send a cue to load firmware for M-Audio " Takashi Sakamoto
2014-02-28  3:27 ` [PATCH 39/39] bebob: Add support for M-Audio special " Takashi Sakamoto
2014-03-01 10:53   ` Stefan Richter
2014-03-01 13:06     ` Takashi Sakamoto
2014-03-01 14:32       ` Stefan Richter
2014-02-28  6:36 ` [GIT PULL][PATCH 00/39] Enhancement of support for Firewire devices Takashi Iwai
2014-03-01 13:14   ` Takashi Sakamoto
     [not found] <5316963F.1000206@sakamocchi.jp>
2014-03-05 10:47 ` [GIT PULL][PATCH 00/39 v2] " Takashi Sakamoto
2014-03-05 10:48   ` [PATCH 18/39] firewire-lib: Add a fallback at RCODE_CANCELLED Takashi Sakamoto

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