Date: Sun, 2 Oct 2005 15:08:29 -0700
From: Pete Zaitcev <zaitcev@redhat.com>
To: Christopher Li <chrisl@vmware.com>
Cc: linux-usb-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org,
       zaitcev@redhat.com
Subject: Re: PATCH] incrase usbdevfs bulk buffer size
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On Sat, 1 Oct 2005 16:20:59 -0400, Christopher Li <chrisl@vmware.com> wrote:

> I hit this limit with running ehci in the VM. The a single ehci
> qTD transfer buffer can be 5 pages long, that is 20K. [...]

Even 16K is too much, IMHO.

> I can complicate the user space part to work around that,
> but it seems much simpler just allow usbdevfs to accept bigger buffers.

It seems, yes. However, I assure you that this is not going to
work for anyone who has anything reasonable swapped out, because
of the kmalloc().

16K is an order 2 allocation on systems with 4KB pages, such as
Opteron. It kinda sorta works, but not really.

This looks like a requirement to think about a better API. Also,
the things that Harald was trying to fix, with pids and signals,
just tell me that something was really wrong from the start.

-- Pete
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