[PATCH] drm/i915/gvt: Refine new_mmio_info to override the added MMIO_reg

[Zhao, Yakui]

On 2018年05月31日 11:41, Zhenyu Wang wrote:
> On 2018.05.31 11:00:00 +0800, Zhao, Yakui wrote:
>>
>>
>> On 2018年06月01日 10:46, Colin Xu wrote:
>>> On 05/31/2018 10:25 AM, Zhao, Yakui wrote:
>>>
>>>> Hi,
>>>>        Any comment about this patch?
>>>>        After the overriding is supported, it can reduce the effect on
>>>> the other platform when adding one
>>>> mmio handle for one specific platform.
>>>>
>>>> Thanks
>>>>        Yakui
>>>
>>> trade-off against the convenience:
>>> - Unnecessary delete and re-add.
>>> - For a specific mmio, it's unclear how it's handled until go through
>>> all init functions, which
>>> transfers the effort to debugging stage, especially for issue with low
>>> fail rate.
>>>
>>
>> Thanks for your comments.
>>
>> Considering the below scenario:
>>     One platform needs to specify one new mmio_handler/attribute for one
>> mmio_reg while this mmio_reg exists one multi platforms. (Also exist on the
>> generic platform).
>>
>> Based on the current implementation, we need to remove this mmio_reg from
>> the generic_mmio_info and then add it for each platform. (Of course it is
>> also ok to refine the callback mmio_handler and add the platform-check). In
>> such case it is not convenient to handle it.
>> If we need to handle it for multiple mmio_regs, it will become one burden
>> especially when the code needs to be rebased frequently.
>>
>> If the overriding is supported, this will be quite simple. We only need to
>> care how to handle the required mmio_reg for one platform and there is no
>> side effect on the other platforms.
>>
> 
> Need specific user of this, I was assuming BXT enabling depends on this,
> but seems not.
> 

BXT enabling has no dependency on the override attribute. But the BXT 
enabling can benefit from it.

Some other platforms are also touched in order to enable the mmio 
handler for BXT in Colin's patch.
https://lists.freedesktop.org/archives/intel-gvt-dev/2018-June/003799.html

If BXT wants to add one specific handler for Pipe/Plane mmio_reg, we 
will have to touch BDW/SKL/KBL/BXT.(pipe/plane mmio_reg are generic for 
the four platforms). The override can allow us to only add it for BXT 
and BDW/SKL/KBL are not affected.

Thanks.
> 
> 
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