On Tue, 2015-10-13 at 16:42 +0200, Lars-Peter Clausen wrote: > On 10/13/2015 04:18 PM, Koro Chen wrote: > > On Tue, 2015-10-13 at 15:44 +0200, Lars-Peter Clausen wrote: > >> On 10/13/2015 03:37 PM, Koro Chen wrote: > >>> The patch "ASoC: Prevent components from being bound to multiple cards" > >>> adds check to prevent multiple cards from using the same component. > >>> However, snd_soc_register_platform() or snd_soc_register_codec() will > >>> also create components, and sharing the same platform by multiple cards > >>> is then refused. This happens with a platform having multiple > >>> independent DAIs that share the same DMA controller. > >>> > >>> Relax the condition by checking component->registered_as_component, > >>> which is only true in case of snd_soc_register_component() and > >>> will be false for components created by snd_soc_register_platform() > >>> or snd_soc_register_codec(). > >> > >> Binding a component to multiple cards results in internal data structure > >> corruption, regardless of whether it is a raw component, CODEC or platform, > >> which is why the check was added. So the proposed change wont work. > >> > > Thanks for your comment. Is it possible to share an example of how the > > data structure will be corrupted? So I can study into this further. > > Just look at soc_probe_component() and think about what happens if that runs > twice for two different cards. Multiple calls to list_add() on the same > list, controls are added multiple times, DAPM widgets are created multiple > times, the card field will only point to the last card. > When multiple binding happens, soc_probe_component() just returns zero without doing anything after this patch (actually it also returned zero before the patch "ASoC: Prevent components from being bound to multiple cards"). So the component still binds to the first card. For this case I think it should be fine?
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