From: Clemens Ladisch <clemens@ladisch.de>
To: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc: alsa-devel@alsa-project.org
Subject: Re: [PATCH] ALSA: usb: refine delay information with USB frame counter
Date: Thu, 25 Aug 2011 09:54:14 +0200 [thread overview]
Message-ID: <4E55FFA6.90506@ladisch.de> (raw)
In-Reply-To: <1314221197-23719-1-git-send-email-pierre-louis.bossart@linux.intel.com>
Pierre-Louis Bossart wrote:
> This patch relies on the USB frame counter ...
> + if (frame_diff < 0)
> + frame_diff += 1024; /* handle 10-bit wrap-around */
After reading through some HCD source files, I deduced the following
wrap-arounds:
EHCI: 8-10 bits (default 9)
FHCI: 11 bits
IMX21: 16 bits
ISP1760: 10 bits
OHCI: 16 bits
OXU210HP: 10 bits
R8A66597: 10 bits
SL811: 5 bits(!?)
UHCI: 32 bits
xHCI: ?
So which hardware did you test this on? :-)
As long as there isn't an API that tells us about the valid range of the
frame counter, we should probably mask off all except the lowest few bits.
Regards,
Clemens
next prev parent reply other threads:[~2011-08-25 7:54 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-24 21:26 [PATCH] ALSA: usb: refine delay information with USB frame counter Pierre-Louis Bossart
2011-08-25 7:54 ` Clemens Ladisch [this message]
2011-08-25 14:00 ` Pierre-Louis Bossart
[not found] ` <002301cc632f$5bfe0a90$13fa1fb0$@bossart@linux.intel.com>
2011-08-25 14:07 ` Clemens Ladisch
-- strict thread matches above, loose matches on Subject: below --
2011-08-29 18:32 Pierre-Louis Bossart
2011-08-30 7:59 ` Clemens Ladisch
2011-08-30 15:34 ` Pierre-Louis Bossart
2011-09-05 7:53 ` Clemens Ladisch
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