From: Oliver Neukum <oneukum@suse.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Alan Stern <stern@rowland.harvard.edu>,
"Steinar H. Gunderson" <sesse@google.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH] Add support for usbfs zerocopy.
Date: Fri, 08 Jan 2016 17:02:07 +0100 [thread overview]
Message-ID: <1452268927.11435.3.camel@suse.com> (raw)
In-Reply-To: <20160108094535.GA17286@infradead.org>
On Fri, 2016-01-08 at 01:45 -0800, Christoph Hellwig wrote:
> On Wed, Jan 06, 2016 at 10:35:05AM -0500, Alan Stern wrote:
> > Indeed, the I/O operations we are using with mmap here are not reads or
> > writes; they are ioctls. As far as I know, the kernel doesn't have any
> > defined interface for zerocopy ioctls.
>
> IF it was using mmap for I/O it would read in through the page fault
> handler an then mark the page dirty for writeback by the VM. Thats
> clearly not the case.
That won't work because we need the ability to determine the chunk size
IO is done in. USB devices don't map to files, yet the memory they can
operate on depends on the device, so allocation in the kernel for
a specific device is a necessity.
Regards
Oliver
next prev parent reply other threads:[~2016-01-08 16:04 UTC|newest]
Thread overview: 41+ 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 20:58 ` Kirill A. Shutemov
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
2016-01-06 15:39 ` Alan Stern
2016-01-06 15:35 ` Alan Stern
2016-01-08 9:45 ` Christoph Hellwig
2016-01-08 10:22 ` David Laight
2016-01-08 16:02 ` Oliver Neukum [this message]
2016-01-12 21:26 ` Steinar H. Gunderson
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
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