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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Takashi Iwai <tiwai@suse.de>
Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>,
	alsa-devel@alsa-project.org, tglx@linutronix.de,
	Jaroslav Kysela <perex@perex.cz>,
	linux-usb@vger.kernel.org
Subject: [4/9,v2] ALSA: usb-audio: use usb_fill_int_urb()
Date: Wed, 20 Jun 2018 15:52:49 +0200	[thread overview]
Message-ID: <20180620135249.rcr4dkka5jkrattl@linutronix.de> (raw)

On 2018-06-20 15:21:49 [+0200], Takashi Iwai wrote:
> > usb_fill_int_urb() ensures that syncinterval is within the allowed range
> > on HS/SS. The interval value seems to come from
> > snd_usb_parse_datainterval() which is bInterval - 1 and only in the rage
> > 1 … 4. So in order to keep the magic working I pass datainterval + 1.
> 
> This needs more explanation.  By this conversion, the interval
> computation becomes really tricky.
> 
> There are two interval calculations.  The first one is
> fp->datainterval and it's from snd_usb_parse_datainterval() as you
> mentioned.  And a tricky part is that fp->datainterval is 0 on
> FULL_SPEED.  Casually, fp->datainterval+1 will be translated to the
> correct value since (0 + 1) == (1 << 0).
> 
> OTOH, for the sync EP, it's taken from ep->syncinterval, which is set
> in snd_usb_add_endpoint().  Luckily, again, ep->syncinterval + 1 works
> for FULL_SPEED as well, as (1 + 1) == (1 << 1).

Do you want me to add your additional explanation to the description?
 
> thanks,
> 
> Takashi

Sebastian
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WARNING: multiple messages have this Message-ID (diff)
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Takashi Iwai <tiwai@suse.de>
Cc: alsa-devel@alsa-project.org, linux-usb@vger.kernel.org,
	tglx@linutronix.de,
	Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Subject: Re: [PATCH 4/9 v2] ALSA: usb-audio: use usb_fill_int_urb()
Date: Wed, 20 Jun 2018 15:52:49 +0200	[thread overview]
Message-ID: <20180620135249.rcr4dkka5jkrattl@linutronix.de> (raw)
In-Reply-To: <s5hlgb9mw42.wl-tiwai@suse.de>

On 2018-06-20 15:21:49 [+0200], Takashi Iwai wrote:
> > usb_fill_int_urb() ensures that syncinterval is within the allowed range
> > on HS/SS. The interval value seems to come from
> > snd_usb_parse_datainterval() which is bInterval - 1 and only in the rage
> > 1 … 4. So in order to keep the magic working I pass datainterval + 1.
> 
> This needs more explanation.  By this conversion, the interval
> computation becomes really tricky.
> 
> There are two interval calculations.  The first one is
> fp->datainterval and it's from snd_usb_parse_datainterval() as you
> mentioned.  And a tricky part is that fp->datainterval is 0 on
> FULL_SPEED.  Casually, fp->datainterval+1 will be translated to the
> correct value since (0 + 1) == (1 << 0).
> 
> OTOH, for the sync EP, it's taken from ep->syncinterval, which is set
> in snd_usb_add_endpoint().  Luckily, again, ep->syncinterval + 1 works
> for FULL_SPEED as well, as (1 + 1) == (1 << 1).

Do you want me to add your additional explanation to the description?
 
> thanks,
> 
> Takashi

Sebastian
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             reply	other threads:[~2018-06-20 13:52 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-20 13:52 Sebastian Andrzej Siewior [this message]
2018-06-20 13:52 ` [PATCH 4/9 v2] ALSA: usb-audio: use usb_fill_int_urb() Sebastian Andrzej Siewior
  -- strict thread matches above, loose matches on Subject: below --
2018-06-22 10:14 [6/9] ALSA: usb: caiaq: " Sebastian Andrzej Siewior
2018-06-22 10:14 ` [PATCH 6/9] " Sebastian Andrzej Siewior
2018-06-22 10:01 [6/9] " Daniel Mack
2018-06-22 10:01 ` [PATCH 6/9] " Daniel Mack
2018-06-22  8:49 [6/9] " Takashi Iwai
2018-06-22  8:49 ` [PATCH 6/9] " Takashi Iwai
2018-06-21 21:16 [6/9] " Sebastian Andrzej Siewior
2018-06-21 21:16 ` [PATCH 6/9] " Sebastian Andrzej Siewior
2018-06-21 20:19 [6/9] " Daniel Mack
2018-06-21 20:19 ` [PATCH 6/9] " Daniel Mack
2018-06-21 20:18 [5/9] ALSA: usb: caiaq: audio: use irqsave() in USB's complete callback Daniel Mack
2018-06-21 20:18 ` [PATCH 5/9] " Daniel Mack
2018-06-20 16:20 [8/9] ALSA: usx2y: usbusx2yaudio: use usb_fill_int_urb() Takashi Iwai
2018-06-20 16:20 ` [PATCH 8/9] " Takashi Iwai
2018-06-20 15:47 [8/9] " Sebastian Andrzej Siewior
2018-06-20 15:47 ` [PATCH 8/9] " Sebastian Andrzej Siewior
2018-06-20 15:38 [8/9] " Sebastian Andrzej Siewior
2018-06-20 15:38 ` [PATCH 8/9] " Sebastian Andrzej Siewior
2018-06-20 14:52 [8/9] " Takashi Iwai
2018-06-20 14:52 ` [PATCH 8/9] " Takashi Iwai
2018-06-20 14:39 [8/9] " Sebastian Andrzej Siewior
2018-06-20 14:39 ` [PATCH 8/9] " Sebastian Andrzej Siewior
2018-06-20 14:00 [4/9,v2] ALSA: usb-audio: " Takashi Iwai
2018-06-20 14:00 ` [PATCH 4/9 v2] " Takashi Iwai
2018-06-20 13:56 [4/9,v2] " Takashi Iwai
2018-06-20 13:56 ` [PATCH 4/9 v2] " Takashi Iwai
2018-06-20 13:21 [4/9,v2] " Takashi Iwai
2018-06-20 13:21 ` [PATCH 4/9 v2] " Takashi Iwai
2018-06-20 12:51 [8/9] ALSA: usx2y: usbusx2yaudio: " Takashi Iwai
2018-06-20 12:51 ` [PATCH 8/9] " Takashi Iwai
2018-06-20  9:38 [4/9,v2] ALSA: usb-audio: " Sebastian Andrzej Siewior
2018-06-20  9:38 ` [PATCH 4/9 v2] " Sebastian Andrzej Siewior
2018-06-20  8:23 [4/9] " Sergei Shtylyov
2018-06-20  8:23 ` [PATCH 4/9] " Sergei Shtylyov
2018-06-19 21:55 [9/9] ALSA: usx2y: usx2yhwdeppcm: " Sebastian Andrzej Siewior
2018-06-19 21:55 ` [PATCH 9/9] " Sebastian Andrzej Siewior
2018-06-19 21:55 [8/9] ALSA: usx2y: usbusx2yaudio: " Sebastian Andrzej Siewior
2018-06-19 21:55 ` [PATCH 8/9] " Sebastian Andrzej Siewior
2018-06-19 21:55 [7/9] ALSA: usb-midi: use irqsave() in USB's complete callback Sebastian Andrzej Siewior
2018-06-19 21:55 ` [PATCH 7/9] " Sebastian Andrzej Siewior
2018-06-19 21:55 [6/9] ALSA: usb: caiaq: use usb_fill_int_urb() Sebastian Andrzej Siewior
2018-06-19 21:55 ` [PATCH 6/9] " Sebastian Andrzej Siewior
2018-06-19 21:55 [5/9] ALSA: usb: caiaq: audio: use irqsave() in USB's complete callback Sebastian Andrzej Siewior
2018-06-19 21:55 ` [PATCH 5/9] " Sebastian Andrzej Siewior
2018-06-19 21:55 [4/9] ALSA: usb-audio: use usb_fill_int_urb() Sebastian Andrzej Siewior
2018-06-19 21:55 ` [PATCH 4/9] " Sebastian Andrzej Siewior
2018-06-19 21:55 [3/9] ALSA: ua101: " Sebastian Andrzej Siewior
2018-06-19 21:55 ` [PATCH 3/9] " Sebastian Andrzej Siewior
2018-06-19 21:55 [2/9] ALSA: line6: " Sebastian Andrzej Siewior
2018-06-19 21:55 ` [PATCH 2/9] " Sebastian Andrzej Siewior
2018-06-19 21:55 [1/9] ALSA: 6fire: " Sebastian Andrzej Siewior
2018-06-19 21:55 ` [PATCH 1/9] " Sebastian Andrzej Siewior
2018-06-19 21:55 ALSA: use irqsave() in URB completion + usb_fill_int_urb Sebastian Andrzej Siewior
2018-06-20 12:55 ` Takashi Iwai

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