RE: [PATCH] Support for write-only controls

["Martin Rubli" <v4l2-lists@xxxxxxxxxx>]

Hi all,

Thanks a lot for all your feedback and the constructive discussion and  
sorry for the delay while I was without Internet on the weekend. I'll try  
to summarize what we have so far:

Write-only controls:

It seems, everybody likes EACCES. Michael, maybe we could get some  
feedback from you on this? It would be nice to change the spec, so that  
EACCES also becomes the error for writing read-only controls--it seems  
appropriate. But if for some reason we can't change that we should  
probably make the write-only controls consistent and return EINVAL as well.

Unusable controls due to device communication error:

The easiest solution seems to be to set the V4L2_CTRL_FLAG_DISABLED flag  
as was suggested. The documentation currently says "permanently disabled  
and should be ignored by the application" which I think is exactly what  
applies to the situation. The V4L2_CTRL_FLAG_NEXT_CTRL would still be  
respected by drivers supporting the extended control enumeration, so no  
need to the spec is required. But I would still add a short paragraph  
about the first part as a guide for future implementations and a witness  
of this thread. ;-)

As soon as everyone agrees on this, I will propose new patches. Let me  
know what you think ...

Cheers,
Martin

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