drm connectors, tegra, and the web they weave (was Re: [PATCH 58/59] drm/todo: Add new debugfs todo)

[Jon Hunter]

On 18/06/2019 16:19, Greg Kroah-Hartman wrote:
> On Fri, Jun 14, 2019 at 10:36:14PM +0200, Daniel Vetter wrote:
>> Greg is busy already, but maybe he won't do everything ...
>>
>> Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
>> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
>> ---
>>  Documentation/gpu/todo.rst | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
>> index 9717540ee28f..026e55c517e1 100644
>> --- a/Documentation/gpu/todo.rst
>> +++ b/Documentation/gpu/todo.rst
>> @@ -375,6 +375,9 @@ There's a bunch of issues with it:
>>    this (together with the drm_minor->drm_device move) would allow us to remove
>>    debugfs_init.
>>  
>> +- Drop the return code and error checking from all debugfs functions. Greg KH is
>> +  working on this already.
> 
> 
> Part of this work was to try to delete drm_debugfs_remove_files().
> 
> There are only 4 files that currently still call this function:
> 	drivers/gpu/drm/tegra/dc.c
> 	drivers/gpu/drm/tegra/dsi.c
> 	drivers/gpu/drm/tegra/hdmi.c
> 	drivers/gpu/drm/tegra/sor.c
> 
> For dc.c, the driver wants to add debugfs files to the struct drm_crtc
> debugfs directory.  Which is fine, but it has to do some special memory
> allocation to get the debugfs callback to point not to the struct
> drm_minor pointer, but rather the drm_crtc structure.
> 
> So, to remove this call, I need to remove this special memory allocation
> and to do that, I need to somehow be able to cast from drm_minor back to
> the drm_crtc structure being used in this driver.  And I can't figure
> how they are related at all.
> 
> Any pointers here (pun intended) would be appreciated.
> 
> For the other 3 files, the situation is much the same, but I need to get
> from a 'struct drm_minor' pointer to a 'struct drm_connector' pointer.
> 
> I could just "open code" a bunch of calls to debugfs_create_file() for
> these drivers, which would solve this issue, but in a more "non-drm"
> way.  Is it worth to just do that instead of overthinking the whole
> thing and trying to squish it into the drm "model" of drm debugfs calls?
> 
> Either way, who can test these changes?  I can't even build the tegra
> driver without digging up an arm64 cross-compiler, and can't test it as
> I have no hardware at all.

We can definitely compile and boot test these no problem. In fact
anything that lands in -next we will boot test. However, I can do some
quick sanity if you have something to test.

Thierry may have more specific Tegra DRM tests.

Cheers
Jon

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