On Tue 2015-02-10 09:14:36, Oliver Neukum wrote:
> On Mon, 2015-02-09 at 20:44 +0200, Lauri Kasanen wrote:
> > On Mon, 09 Feb 2015 11:08:01 +0100
> > Oliver Neukum <[email protected]> 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.
Should we have some kind of runtime test for this ...? Because this is
very very easy to get wrong... and I bet we do get it wrong at > 1
place...
Pavel
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