From: Oliver Neukum <oneukum@suse.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Lingzhu Xiang <lingzhu.xiang@mail.utoronto.ca>,
"Steinar H. Gunderson" <sesse@google.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
USB list <linux-usb@vger.kernel.org>,
Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] Add support for usbfs zerocopy.
Date: Mon, 11 Jan 2016 12:08:26 +0100 [thread overview]
Message-ID: <1452510506.3907.3.camel@suse.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1601071035060.1537-100000@iolanthe.rowland.org>
On Thu, 2016-01-07 at 10:40 -0500, Alan Stern wrote:
> > I understand there are some requirements on the allocation such that
> > large blocks are not always available. But what is the proper way to
> > determine the upper limit of the size such that the user can avoid
> > generating warnings like this? (Also, the application really wants
> to
> > be able to allocate large buffers, maybe tune swiotlb=?.)
>
> It's debatable whether this should have generated a warning. Why
> doesn't dma_alloc_coherent() simply fail silently?
I suspect many drivers to be unable to deal well with a failure.
Having this report makes "my device doesn't work" easier to solve
as a bug report.
Hence it seems to me that a driver which can handle a failure
with a good fallback should indicate this with a flag to the
VM layer.
Regards
Oliver
next prev parent reply other threads:[~2016-01-11 11:10 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 [this message]
[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
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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