linux-kernel - Re: [PATCH v4 00/17] ALSA: hda: cirrus: Add initial DSP support and firmware loading

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Date:   Mon, 30 May 2022 09:36:39 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Takashi Iwai <tiwai@...e.de>
CC:     Vitaly Rodionov <vitalyr@...nsource.cirrus.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, Mark Brown <broonie@...nel.org>,
        <alsa-devel@...a-project.org>, <patches@...nsource.cirrus.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 00/17] ALSA: hda: cirrus: Add initial DSP support and
 firmware loading

On Mon, May 30, 2022 at 11:18:43AM +0200, Takashi Iwai wrote:
> On Mon, 30 May 2022 11:08:46 +0200,
> Charles Keepax wrote:
> > 
> > On Fri, May 27, 2022 at 06:13:38PM +0200, Takashi Iwai wrote:
> > > On Wed, 25 May 2022 15:16:21 +0200,
> > > Vitaly Rodionov wrote:
> > > The idea to add / delete controls by the control element change
> > > doesn't sound good; as already mentioned in my reply to the previous
> > > patch set, the change of the control elements can be triggered too
> > > easily by any normal users who have the access to the sound devices.
> > > It means thousands of additions and removals per second could be
> > > attacked by any user.
> > > 
> > 
> > This I am a little less sure how we handle. I mean arn't there
> > already a few ways to do this? Both the existing ASoC wm_adsp
> > stuff, and the topology stuff (used on all new Intel platforms,
> > so very widely deployed) let you create controls by loading a
> > firmware file. Also within ALSA itself can't user-space create
> > user ALSA controls? Is there some rate limiting on that? How is
> > this issue tackled there?
> 
> The creation of kctls via firmware loading would be OK, as the code
> path can't be triggered so frequently.  Is it the case for this patch
> set?  There was too little information about the implementation (and
> more importantly, how to use the controls), so it's hard to judge...
> 

Yeah that should be what is happening here. Although it looks
like this code might be removing all the controls if the firmware
is unloaded. I will discuss that with the guys, we normal just
disable the controls on the wm_adsp stuff.

Thanks,
Charles