[Intel-xe] [PATCH] drm/xe/uapi: Remove MMIO ioctl

[Ofir Bitton]

On 14/09/2023 11:35, Jani Nikula wrote:
> On Tue, 12 Sep 2023, Ofir Bitton <obitton at habana.ai> wrote:
>> On 12/09/2023 14:11, Jani Nikula wrote:
>>> On Tue, 12 Sep 2023, Ofir Bitton <obitton at habana.ai> wrote:
>>>> On 12/09/2023 3:25, Matt Roper wrote:
>>>> Hey Matt, I totally undesrstand your concern, I might have another
>>>> suggestion. We can create another FD in debugfs and move this ioctl
>>>> there (I can take ownership on this), This way ABI is not an issue.
>>>
>>> FD or ioctl in debugfs? Or do you just mean adding a debugfs file for
>>> register access?
>>>
>>> BR,
>>> Jani.
>>>
>>
>> Add a new file in debugfs to which we will send debug ioctls such as the
>> mmio ioctl.
> 
> It's so rare to do ioctl on debugfs files that I first had to check it's
> possible, and then try to find examples in the kernel. I found one so
> far, though there are probably more.
> 
> If it's that rare, usually the question is, does it make sense?
> 
> 
> BR,
> Jani.
> 
> 

I actually got this idea from Daniel few months back during a different
discussion. Daniel any thoughts on this?

If you are uncomfortable with the ioctl approach we can go with a 
different approach, for example what we did in the habanalabs driver:

setting read/write address:
https://elixir.bootlin.com/linux/v6.6-rc1/source/drivers/accel/habanalabs/common/debugfs.c#L1630

read32:
https://elixir.bootlin.com/linux/v6.6-rc1/source/drivers/accel/habanalabs/common/debugfs.c#L844

I liked the ioctl approach so much because it requires a single system
call instead of 2 and the implementation is much cleaner.

Ofir.