From mboxrd@z Thu Jan  1 00:00:00 1970
MIME-Version: 1.0
Message-ID: <trinity-3c4db376-060d-497f-906c-2044527d8ed2-1365685758745@3capp-gmx-bs34>
From: "kernel panic" <cinap_lenrek@gmx.de>
To: "Fans of the OS Plan 9 from Bell Labs" <9fans@9fans.net>
Content-Type: text/plain; charset=UTF-8
Date: Thu, 11 Apr 2013 15:09:18 +0200
In-Reply-To: <89ec832d7e467386a2f36d83033d0c6b@kw.quanstro.net>
References: <trinity-4dc553a9-048b-4476-b21b-57056db11e8e-1365679501436@3capp-gmx-bs34>,
	<89ec832d7e467386a2f36d83033d0c6b@kw.quanstro.net>
Subject: Re: [9fans] Tdmaxpkt in usbehci (no html)
Topicbox-Message-UUID: 40d287fc-ead8-11e9-9d60-3106f5b1d025

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
>
>