From: "kernel panic" <cinap_lenrek@gmx.de>
To: "Fans of the OS Plan 9 from Bell Labs" <9fans@9fans.net>
Subject: Re: [9fans] Tdmaxpkt in usbehci (no html)
Date: Thu, 11 Apr 2013 15:09:18 +0200 [thread overview]
Message-ID: <trinity-3c4db376-060d-497f-906c-2044527d8ed2-1365685758745@3capp-gmx-bs34> (raw)
In-Reply-To: <89ec832d7e467386a2f36d83033d0c6b@kw.quanstro.net>
yes, that would work too.
--
cinap
> Gesendet: Donnerstag, 11. April 2013 um 15:05 Uhr
> Von: "erik quanstrom" <quanstro@quanstro.net>
> An: 9fans@9fans.net
> Betreff: Re: [9fans] Tdmaxpkt in usbehci (no html)
>
> > in the ehci driver, it uses:
> >
> > Tdmaxpkt = 0x5000, /* max buffer for a Td */
> >
> > a td has 5*4K pages giving the 20K above, but i think this only applies if the
> > first pointer is page aligned (page offset = 0) so all the pages can be filled
> > completely.
> >
> > The EHCI spec says this:
> > "The buffer pointer list in the qTD is long enough to support a maximum transfer size of 20K bytes. This case
> > occurs when all five buffer pointers are used and the first offset is zero. A qTD handles a 16Kbyte buffer
> > with any starting buffer alignment."
> >
> > The buffer pointer isnt page aligned as far as i can see, so make Tdmaxpkt = 0x4000 instead?
>
> i wonder if it would make more sense to align the buffer.
>
> (the unaligned case for iso->data looks wierd, too.)
>
> - erik
>
>
prev parent reply other threads:[~2013-04-11 13:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-11 11:25 cinap_lenrek
2013-04-11 13:05 ` erik quanstrom
2013-04-11 13:09 ` kernel panic [this message]
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