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    SubjectRe: [alsa-devel] [PATCH v2 09/11] ASoC: Intel: hdac_hdmi: Set ops to NULL on remove
    On Tue, 18 Jun 2019 06:19:15 +0200,
    Ranjani Sridharan wrote:
    >
    > On Mon, 2019-06-17 at 23:36 +0200, Takashi Iwai wrote:
    > > On Mon, 17 Jun 2019 22:51:42 +0200,
    > > Ranjani Sridharan wrote:
    > > >
    > > > On Mon, 2019-06-17 at 13:36 +0200, Amadeusz Sławiński wrote:
    > > > > When we unload Skylake driver we may end up calling
    > > > > hdac_component_master_unbind(), it uses acomp->audio_ops, which
    > > > > we
    > > > > set
    > > > > in hdmi_codec_probe(), so we need to set it to NULL in
    > > > > hdmi_codec_remove(),
    > > > > otherwise we will dereference no longer existing pointer.
    > > >
    > > > Hi Amadeusz,
    > > >
    > > > It looks like the audio_ops should be deleted
    > > > snd_hdac_acomp_exit().
    > >
    > > It's a different one. The codec driver registers / de-registers the
    > > notifier at its probe/remove, while the controller driver takes care
    > > of snd_hdac_acomp_init(). snd_hdac_acomp_exit() is usually not
    > > needed
    > > to be called explicitly, as it's managed via devres.
    >
    > Makes sense, thanks Takashi. But I am still wondering why we havent
    > seen this issue with SOF yet. We run the module unload/reload stress
    > test as well and havent seen this yet.

    Usually this isn't a problem as the controller is removed at first.
    But if the codec is unbound at first by some reason, it can be a
    problem without unregistering, I guess.


    Takashi

    >
    > Thanks,
    > Ranjani
    > >
    > >
    > > Takashi
    > >
    > > > Also, this doesnt seem to be the case with when the SOF driver is
    > > > removed.
    > > > Could you please give a bit more context on what error you see when
    > > > this happens?
    > > >
    > > > Thanks,
    > > > Ranjani
    > > > >
    > > > > Signed-off-by: Amadeusz Sławiński <
    > > > > amadeuszx.slawinski@linux.intel.com>
    > > > > ---
    > > > > sound/soc/codecs/hdac_hdmi.c | 6 ++++++
    > > > > 1 file changed, 6 insertions(+)
    > > > >
    > > > > diff --git a/sound/soc/codecs/hdac_hdmi.c
    > > > > b/sound/soc/codecs/hdac_hdmi.c
    > > > > index 911bb6e2a1ac..9ee1bff548d8 100644
    > > > > --- a/sound/soc/codecs/hdac_hdmi.c
    > > > > +++ b/sound/soc/codecs/hdac_hdmi.c
    > > > > @@ -1890,6 +1890,12 @@ static void hdmi_codec_remove(struct
    > > > > snd_soc_component *component)
    > > > > {
    > > > > struct hdac_hdmi_priv *hdmi =
    > > > > snd_soc_component_get_drvdata(component);
    > > > > struct hdac_device *hdev = hdmi->hdev;
    > > > > + int ret;
    > > > > +
    > > > > + ret = snd_hdac_acomp_register_notifier(hdev->bus, NULL);
    > > > > + if (ret < 0)
    > > > > + dev_err(&hdev->dev, "notifier unregister failed: err:
    > > > > %d\n",
    > > > > + ret);
    > > > >
    > > > > pm_runtime_disable(&hdev->dev);
    > > > > }
    > > >
    > > >
    >

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