Hi Jani
On 2020-04-06 02:11, Jani Nikula wrote:
On Fri, 03 Apr 2020, abhinavk@xxxxxxxxxxxxxx wrote:
Hi Ville
Thanks for the patch.
Our understanding of private_flags was that we can use it within our
drivers to handle vendor specific features.
Hence we do have several features in our downstream drivers as well as
some planned work based on this.
This was the only method to pass around and consume the driver only
information which we have been using.
In the current qualcomm upstream display drivers, the only usage of
the
mode->private_flags is what you have removed in
https://patchwork.kernel.org/patch/11473497/.
However, for other projects which do not use upstream drivers yet, we
have several features already which are using the mode->private_flags.
We do have a plan to remove the usage of mode->private_flags for those
drivers as well but its not ready yet.
These downstream drivers still use the upstream drm files for
compilation.
So how it works is we use all the headers under include/drm and also
the
files under drivers/gpu/drm as-it-is from upstream but maintain our
drivers on top of this.
Removing this will result in compilation failures for us in the near
term.
Can we keep this one as-it-is and when our changes are ready to post
it
upstream we shall remove private_flags from the drm_modes.h
If your driver were upstream, Ville would have fixed it in the process
of removing private_flags. It would be part of this patch series. That
is the only guarantee you get for kernel internal APIs, and you only
get
that guarantee for drivers in the upstream kernel. Otherwise, all bets
are off.
Taking all the upstream considerations into account is complicated
enough. It is simply not reasonable to hold back internal kernel
changes
due to out-of-tree or downstream drivers. I know it is painful, but
that's the cost of maintaining a driver out-of-tree.
Sorry, but no. Further reading [1].
BR,
Jani.
[1]
https://www.kernel.org/doc/html/latest/process/stable-api-nonsense.html
Thanks for the response. We will plan to remove mode->private_flags in
our downstream driver as well.
Abhinav
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