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Message-ID: <1423556076.19839.3.camel@linux-0dmf.site>
Date: Tue, 10 Feb 2015 09:14:36 +0100
From: Oliver Neukum <oneukum@...e.de>
To: Lauri Kasanen <cand@....com>
Cc: jkosina@...e.cz, linux-input@...r.kernel.org,
linux-kernel@...r.kernel.org, ao2@....it, AndrewD207@....com
Subject: Re: [PATCH] HID: sony: Enable Gasia third-party PS3 controllers
On Mon, 2015-02-09 at 20:44 +0200, Lauri Kasanen wrote:
> On Mon, 09 Feb 2015 11:08:01 +0100
> Oliver Neukum <oneukum@...e.de> wrote:
>
> > > + ret = usb_interrupt_msg(dev, usb_sndintpipe(dev, 0x02),
> > > + buf2, sizeof(buf2),
> > > + &transfered, USB_CTRL_SET_TIMEOUT);
> >
> > You cannot do this. Even for a single byte DMA on the stack is
> > wrong. Not on all architectures it works at all and you violate
> > the DMA constrainsts. You must use kmalloc().
>
> Hi Oliver,
>
> Does this still apply when using hid_hw_output_report?
Yes. For USB devices hid_hw_output_report() goes to
usbhid_output_report(). That goes to usb_interrupt_msg(),
which passes the buffer pointer. It will then be mapped
for DMA. You must not do that on the stack.
HTH
Oliver
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