From: David Brownell <david-b@pacbell.net>
To: Jens Axboe <axboe@suse.de>
Cc: Alan Stern <stern@rowland.harvard.edu>,
Nicolas Mailhot <Nicolas.Mailhot@laPoste.net>,
USB development list <linux-usb-devel@lists.sourceforge.net>,
linux-kernel@vger.kernel.org
Subject: Re: [linux-usb-devel] Re: [Bug 1412] Copy from USB1 CF/SM reader stalls, no actual content is read (only directory structure)
Date: Fri, 07 Nov 2003 10:56:48 -0800 [thread overview]
Message-ID: <3FABEAF0.9060000@pacbell.net> (raw)
In-Reply-To: <20031107082439.GB504@suse.de>
Jens Axboe wrote:
> No that looks alright, given you are allocating low memory pages. The
> devices can probably do full 32-bit dma I bet, though.
Typically ... most usb host controllers you'll see are on
PCI (OHCI, UHCI, EHCI) with no restrictions, and only some
EHCI controllers can do 64-bit DMA. That's all visible in
the the dma_mask for each interface in the device with the
mass storage support, usually still at its "32-bit dma is ok"
pci controller default.
But it seems that most current 2.6 DMA API implementations
have some problems in those areas. See for example:
http://marc.theaimsgroup.com/?l=linux-kernel&m=106746453218943&w=2
http://marc.theaimsgroup.com/?l=linux-usb-devel&m=106789996221347&w=2
That second patch is a partial workaround for the first patch
presumably not getting applied before 2.6.0-final. Net result,
some systems with gobs of memory and no IOMMU may do needless
buffer copies during USB I/O.
Though a quick glance suggested to me that SCSI infrastructure
is consulting dma_mask directly, instead of using the DMA API
calls which do that. I'm not sure I'd trust it to be any
more correct, given GIGO ...
- Dave
prev parent reply other threads:[~2003-11-07 23:54 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1067633171.3886.1.camel@m70.net81-64-235.noos.fr>
2003-11-01 15:47 ` [Bug 1412] Copy from USB1 CF/SM reader stalls, no actual content is read (only directory structure) Alan Stern
2003-11-04 7:49 ` Jens Axboe
2003-11-04 17:33 ` Alan Stern
2003-11-05 8:40 ` Jens Axboe
2003-11-05 15:47 ` Alan Stern
2003-11-07 8:24 ` Jens Axboe
2003-11-07 8:50 ` Nicolas Mailhot
2003-11-07 9:09 ` Jens Axboe
2003-11-07 9:25 ` Nicolas Mailhot
2003-11-07 21:02 ` Nicolas Mailhot
2003-11-07 21:03 ` Nicolas Mailhot
2003-11-07 21:22 ` Jens Axboe
2003-11-07 15:48 ` Alan Stern
2003-11-07 21:22 ` Jens Axboe
2003-11-07 18:56 ` David Brownell [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=3FABEAF0.9060000@pacbell.net \
--to=david-b@pacbell.net \
--cc=Nicolas.Mailhot@laPoste.net \
--cc=axboe@suse.de \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb-devel@lists.sourceforge.net \
--cc=stern@rowland.harvard.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).