linux-kernel - Re: [PATCH] ASoC: pcm512x: Mend accesses to the I2S_1 and I2S

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20210921111128.GA4203@sirena.org.uk>
Date:   Tue, 21 Sep 2021 12:11:28 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Peter Rosin <peda@...ntia.se>
Cc:     Péter Ujfalusi <peter.ujfalusi@...il.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Kirill Marinushkin <kmarinushkin@...dec.com>
Subject: Re: [PATCH] ASoC: pcm512x: Mend accesses to the I2S_1 and I2S_2
 registers

On Tue, Sep 21, 2021 at 08:37:28AM +0200, Peter Rosin wrote:

> I expected it to just work to mark the register as readable and do
> without the default value (i.e. the way it was before my patch). What
> I don't understand is why regmap returns -EBUSY in that case. That
> doesn't make sense to me. Perhaps that -EBUSY is propagated from the
> I2C layer, but in that case, why is it then ok to do a write to
> another register at the same spot in the code? So, why -EBUSY?

Actually one thing that can trigger this now I think about it is
attempting to access a volatile register when the device is in cache
only mode for power management reasons - if the device is in cache only
mode then you can't do a hardware read so volatile registers become
inaccessible.

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)