On 2023-01-17 4:48 PM, Pierre-Louis Bossart wrote:
On 1/17/23 09:47, Cezary Rojewski wrote:
Several functions that take part in codec's initialization and removal
are re-used by ASoC codec drivers implementations. Drivers mimic the
behavior of hda_codec_driver_probe/remove() found in
sound/pci/hda/hda_bind.c with their component->probe/remove() instead.
One of the reasons for that is the expectation of
snd_hda_codec_device_new() to receive a valid struct snd_card pointer
what cannot be fulfilled on ASoC side until a card is attempted to be
very hard to follow.
Is there a spurious 'what' to be removed?
Or is there missing text?
Please consider rewording with simpler sentences.
Thanks for the comments. 'what' is here on purpose as to my ear this
sentence sounds reasonable, but I'm not a native English speaker so I
might be wrong here.
The following is being explained by the commit message:
- functions such as snd_hda_codec_device_new() expect a valid pointer to
struct snd_card instance
- for ASoC hda codec drivers, when hdev_attach/detach() are called,
there is no possibility to provide one to HDAudio API as card components
are not yet enumerated
- once component->probe() is invoked and succeeds, component->card will
point to a valid sound card
- hda codec driver is now ready to call snd_hda_codec_device_new()
bound and its component probing is triggered.
As ASoC sound card may be unbound without codec device being actually
removed from the system, unsetting ->preset in
snd_hda_codec_cleanup_for_unbind() interferes with module unload -> load
scenario causing null-ptr-deref. Preset is assigned only once, during
device/driver matching whereas ASoC codec driver's module reloading may
occur several times throughout the lifetime of an audio stack.
Signed-off-by: Cezary Rojewski <cezary.rojewski@xxxxxxxxx>
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