From: Oliver Neukum <oneukum@suse.de>
To: Florian Mickler <florian@mickler.org>
Cc: "Roedel, Joerg" <Joerg.Roedel@amd.com>,
"Greg Kroah-Hartman" <greg@kroah.com>,
"janne-dvb@grunau.be" <janne-dvb@grunau.be>,
"g.marco@freenet.de" <g.marco@freenet.de>,
"tskd2@yahoo.co.jp" <tskd2@yahoo.co.jp>,
"liplianin@me.by" <liplianin@me.by>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"pb@linuxtv.org" <pb@linuxtv.org>,
"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>,
"max@veneto.com" <max@veneto.com>,
"mchehab@infradead.org" <mchehab@infradead.org>,
"aet@rasterburn.org" <aet@rasterburn.org>,
"mkrufky@linuxtv.org" <mkrufky@linuxtv.org>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
"js@linuxtv.org" <js@linuxtv.org>,
"Rafael J. Wysocki" <rjw@sisk.pl>,
Andy Walls <awalls@md.metrocast.net>,
"nick@nick-andrew.net" <nick@nick-andrew.net>
Subject: Re: [PATCH 0/6] get rid of on-stack dma buffers
Date: Tue, 22 Mar 2011 14:12:46 +0100 [thread overview]
Message-ID: <201103221412.46507.oneukum@suse.de> (raw)
In-Reply-To: <AANLkTimXobrwc-XHgoVN1dD5NCTde64dykbyvtJMo229@mail.gmail.com>
Am Dienstag, 22. März 2011, 14:08:17 schrieb Florian Mickler:
> Am 22.03.2011 12:10 schrieb "Roedel, Joerg" <Joerg.Roedel@amd.com>:
> >
> > On Mon, Mar 21, 2011 at 05:03:15PM -0400, Florian Mickler wrote:
> > > I guess (not verified), that the dma api takes sufficient precautions
> > > to abort the dma transfer if a timeout happens. So freeing _should_
> > > not be an issue. (At least, I would expect big fat warnings everywhere
> > > if that were the case)
> >
> > Freeing is very well an issue. All you can expect from the DMA-API is to
> > give you a valid DMA handle for your device. But it can not prevent that
> > a device uses this handle after you returned it. You need to make sure
> > yourself that any pending DMA is canceled before calling kfree().
>
> Does usb_control_msg do this? It waits for completion but takes also a
> timeout parameter. I will recheck this once I'm home.
It uses usb_start_wait_urb() which upon a timeout kills the URB. The
buffer is unused after usb_control_msg() returns.
HTH
Oliver
next prev parent reply other threads:[~2011-03-22 13:12 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-21 18:33 [PATCH 0/6] get rid of on-stack dma buffers Florian Mickler
2011-03-21 18:33 ` [PATCH 1/6] [media] a800: " Florian Mickler
2011-03-21 18:33 ` [PATCH 2/6 v2] [media] vp7045: " Florian Mickler
2011-03-21 18:33 ` [PATCH 3/6] [media] friio: " Florian Mickler
2011-03-21 18:33 ` [PATCH 4/6] [media] dw2102: get rid of on-stack dma buffer Florian Mickler
2011-03-21 18:33 ` [PATCH 5/6] [media] m920x: get rid of on-stack dma buffers Florian Mickler
2011-03-21 18:33 ` [PATCH 6/6] [media] opera1: get rid of on-stack dma buffer Florian Mickler
2011-03-21 19:26 ` [PATCH 0/6] get rid of on-stack dma buffers Andy Walls
2011-03-21 21:03 ` Florian Mickler
2011-03-22 10:44 ` Roedel, Joerg
[not found] ` <AANLkTimXobrwc-XHgoVN1dD5NCTde64dykbyvtJMo229@mail.gmail.com>
2011-03-22 13:12 ` Oliver Neukum [this message]
2011-03-22 14:27 ` Florian Mickler
2011-03-22 10:59 ` Jiri Kosina
2011-03-22 12:33 ` Johannes Stezenbach
2011-03-22 13:35 ` James Bottomley
2011-03-22 14:02 ` Florian Mickler
2011-03-22 20:15 ` David Miller
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