Re: Design review request: DRM color manager

Sharma, Shashank
2014-05-12T12:05:13Z

Thanks for your time and the comments David.
please find mine inline.

Regards
Shashank
On 5/12/2014 5:20 PM, David Herrmann wrote:
> Hi
>
> On Mon, May 12, 2014 at 12:26 PM, Sharma, Shashank
> <shashank.sharma@intel.com> wrote:
>> Benefits of using color manager:
>> ================================
>> 1. Unique framework for all the color correction properties, across all
>> DRM drivers, across various platforms.
>> 2. Only one set/get call for all kind of properties using the common
>> protocol. One get call can tell what are the color correction capabilities
>> of the SOC, registered by driver.
>
> What's the advantage of that? We should add a
> DRM_MODE_OBJ_SET_PROPERTIES call if we want to accelerate things,
> instead of adding huge payloads.
>
The problem here is a DRM_OBJECT_MODE_SET_PROPERTIES call can pass
limited value. But there are few properties like gamma correction which
need a full LUT(256 vals) to be passed according to the correction
values. The plan here is pretty much aligned to your suggestion, ie to
use DRM_OBJECT_MODE_SET_BLOB kind of property, and extract the data from
the blob based on a protocol.
Why do you think its a huge payload ?
> I really think we should define one property for each color-correction
> interface. I cannot see any downside of that except that we should add
> DRM_MODE_OBJ_SET_PROPERTIES.

As I was discussing, if there are 10 color correction properties a SOC
supports, we have to create 10 properties which doesn't look good, when
all the properties will do the same (set/reset few registers as
correction). We already have a case where we expose 6 different type of
corrections.

One more benefit is, this part is centrally controlled, so you can
always know what's the state of color correction in single shot at any
time. This will also provide us to do a lot of common things to do at
the same place, like floating point arithmetic to register value
conversion in a supporting userspace library, which might be required
for many cases.

INHO, its always good to have a controlled interface/ framework to have
similar things aligned to.

But afaik that's already the plan for
> atomic-modesetting, right?
>
> Thanks
> David
>
AFAIK color management is not a part of atomic modeset, but once we
create such an interface, it would be really easy to club that in the
atomic modeset.