From: "Steinar H. Gunderson" <sesse@google.com>
To: Peter Stuge <peter@stuge.se>
Cc: Christoph Hellwig <hch@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
stern@rowland.harvard.edu
Subject: Re: [PATCH] Add support for usbfs zerocopy.
Date: Wed, 6 Jan 2016 16:36:01 +0100 [thread overview]
Message-ID: <20160106153601.GA25632@imap.gmail.com> (raw)
In-Reply-To: <20160106152212.15218.qmail@stuge.se>
On Wed, Jan 06, 2016 at 04:22:12PM +0100, Peter Stuge wrote:
>>> Our interface for zero copy reads/writes is O_DIRECT, and that requires
>>> not special memory allocation, just proper alignment.
>> But that assumes you are using I/O using read()/write(). There's no way you
>> can shoehorn USB isochronous reads into the read() interface, O_DIRECT or not.
> How about aio?
I don't really see how; a USB device does not look much like a file. (Where
would you stick the endpoint, for one? And how would you ever submit an URB
with multiple packets in it, which is essential?) It feels a bit like
trying to use UDP sockets with only read() and write().
In any case, the usbfs interface already exists and is stable. This is about
extending it; replacing it with something new from scratch to get zerocopy
would seem overkill.
/* Steinar */
--
Software Engineer, Google Switzerland
next prev parent reply other threads:[~2016-01-06 15:36 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <Pine.LNX.4.44L0.1601051024110.1666-100000@iolanthe.rowland.org>
2016-01-05 16:27 ` Does vm_operations_struct require a .owner field? Alan Stern
2016-01-05 16:27 ` Alan Stern
2016-01-05 20:58 ` Kirill A. Shutemov
2016-01-05 20:58 ` Kirill A. Shutemov
2016-01-05 21:31 ` Alan Stern
2016-01-05 21:31 ` Alan Stern
2015-11-26 0:19 ` [PATCH] Add support for usbfs zerocopy Steinar H. Gunderson
2016-01-06 0:11 ` Greg Kroah-Hartman
2015-11-26 0:19 ` [PATCH v2] " Steinar H. Gunderson
2016-01-07 2:01 ` Lingzhu Xiang
2016-01-07 15:40 ` Alan Stern
2016-01-11 11:08 ` Oliver Neukum
[not found] ` <20160111161504.GG10641@char.us.oracle.com>
2016-01-12 10:00 ` Oliver Neukum
2016-01-09 4:00 ` Lingzhu Xiang
2016-01-09 10:57 ` Steinar H. Gunderson
2016-01-24 21:12 ` Greg Kroah-Hartman
2016-01-25 8:03 ` Steinar H. Gunderson
2016-02-02 10:34 ` Steinar H. Gunderson
2016-02-03 21:23 ` Greg Kroah-Hartman
2016-02-03 21:58 ` [PATCH v4] " Steinar H. Gunderson
2016-02-03 22:09 ` [PATCH v2] " Steinar H. Gunderson
2016-02-03 22:15 ` Felipe Balbi
2016-02-03 23:40 ` Steinar H. Gunderson
2016-02-04 10:17 ` Bjørn Mork
2016-02-04 10:26 ` Steinar H. Gunderson
2016-02-12 20:55 ` Steinar H. Gunderson
2016-01-06 0:24 ` [PATCH] " Steinar H. Gunderson
2016-01-06 6:49 ` Christoph Hellwig
2016-01-06 14:45 ` Steinar H. Gunderson
2016-01-06 15:22 ` Peter Stuge
2016-01-06 15:36 ` Steinar H. Gunderson [this message]
2016-01-06 15:39 ` Alan Stern
2016-01-06 15:35 ` Alan Stern
2016-01-08 9:45 ` Christoph Hellwig
2016-01-08 9:45 ` Christoph Hellwig
2016-01-08 10:22 ` David Laight
2016-01-08 10:22 ` David Laight
2016-01-08 16:02 ` Oliver Neukum
2016-01-08 16:02 ` Oliver Neukum
2016-01-12 21:26 ` Steinar H. Gunderson
2016-01-12 21:26 ` Steinar H. Gunderson
2016-01-12 22:05 ` Alan Stern
2016-01-12 22:05 ` Alan Stern
2016-01-13 6:59 ` Lingzhu Xiang
2016-01-13 17:21 ` Greg Kroah-Hartman
2016-01-08 9:43 ` Christoph Hellwig
2016-02-24 19:30 ` Sasha Levin
2016-02-24 19:33 ` Steinar H. Gunderson
2016-01-05 23:54 ` Does vm_operations_struct require a .owner field? Steinar H. Gunderson
2016-01-05 23:54 ` Steinar H. Gunderson
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