linux-kernel - Re: [alsa-devel] USB transfer_buffer allocations on 64bit systems

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 11 May 2010 18:09:23 +0200
From:	Daniel Mack <daniel@...aq.de>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>, gregkh@...e.de,
	konrad.wilk@...cle.com, tiwai@...e.de,
	USB list <linux-usb@...r.kernel.org>, clemens@...isch.de,
	Kernel development list <linux-kernel@...r.kernel.org>,
	chrisw@...s-sol.org, iommu@...ts.linux-foundation.org,
	andi@...stfloor.org, pedrib@...il.com,
	Andrew Morton <akpm@...ux-foundation.org>, dwmw2@...radead.org
Subject: Re: [alsa-devel] USB transfer_buffer allocations on 64bit systems

On Tue, May 11, 2010 at 12:06:09PM -0400, Alan Stern wrote:
> On Wed, 12 May 2010, FUJITA Tomonori wrote:
> 
> > > > Can you tell me all the exact process of DMA that the usb core and the
> > > > driver do?
> > > 
> > > 1. The audio driver stores data in urb->transfer_buffer.
> > 
> > How urb->transfer_buffer is allocated?
> 
> By kmalloc().  Right, Daniel?

Yes, and that's precisely the reason for the whole thread ;)

[...]

> > The driver does only DMA_TO_DEVICE? Or you see DMA problems only with
> > DMA_TO_DEVICE?
> 
> The particular test that Pedro is running uses audio output only -- 
> he's sending sound data to a speaker and it comes out noisy.
> 
> But the audio data has to come from somewhere, and I don't remember 
> where.  Pedro, does the noise occur only when you're playing sound that 
> comes from a different USB device?  What happens if you play sounds 
> that are stored on your hard disk, like an MP3 file?

AFAIK that was playback from a file, yes. It would be interesting to
have some results for the other direction as well, that's true.

Thanks,
Daniel

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/