[PATCH 2/3] drm/doc: Drop chapter "KMS Initialization and Cleanup"

[Kazlauskas, Nicholas]

On 1/30/19 4:02 PM, Daniel Vetter wrote:
> On Wed, Jan 30, 2019 at 05:33:00PM +0000, Kazlauskas, Nicholas wrote:
>> On 1/30/19 11:30 AM, Daniel Vetter wrote:
>>> It only talks about crtc, brings up intel as an exampel and I think is
>>
>> nit: Should be "example".
> 
> Will fix when applying.
> 
>>> more misleading than useful really. Plus we have lots of discussion
>>> about how your standard kms driver should be initialized/cleaned up,
>>> so maybe better to document this when we have a better idea.
>>>
>>> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
>>> ---
>>>    Documentation/gpu/drm-kms.rst | 96 -----------------------------------
>>>    1 file changed, 96 deletions(-)
>>>
>>> diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst
>>> index 75c882e09fee..23a3c986ef6d 100644
>>> --- a/Documentation/gpu/drm-kms.rst
>>> +++ b/Documentation/gpu/drm-kms.rst
>>> @@ -410,102 +410,6 @@ Encoder Functions Reference
>>>    .. kernel-doc:: drivers/gpu/drm/drm_encoder.c
>>>       :export:
>>>    
>>> -KMS Initialization and Cleanup
>>> -==============================
>>> -
>>> -A KMS device is abstracted and exposed as a set of planes, CRTCs,
>>> -encoders and connectors. KMS drivers must thus create and initialize all
>>> -those objects at load time after initializing mode setting.
>>> -
>>> -CRTCs (:c:type:`struct drm_crtc <drm_crtc>`)
>>> ---------------------------------------------
>>> -
>>> -A CRTC is an abstraction representing a part of the chip that contains a
>>> -pointer to a scanout buffer. Therefore, the number of CRTCs available
>>> -determines how many independent scanout buffers can be active at any
>>> -given time. The CRTC structure contains several fields to support this:
>>> -a pointer to some video memory (abstracted as a frame buffer object), a
>>> -display mode, and an (x, y) offset into the video memory to support
>>> -panning or configurations where one piece of video memory spans multiple
>>> -CRTCs.
>>
>> This is mostly a duplicate of what's already in the CRTC abstraction
>> section but it may be worth carrying over the bit about  "the number of
>> CRTCs available determining the number of independent scanout buffers
>> that can be active at any given time".
> 
> Oh I didn't even read this. This is just plain wrong and probably predates
> drm_plane (when it kinda was true-ish, if you'd ignore cursors). Now this
> would map to number of drm_planes, except
> - cursors can still be an exceptions
> - yuv multi-planar might or might not be multiple planes per drm_plane.
> 
> Aka it's really complicated :-)
> 
> This is definitely much better explained in the kms overview section at
> the top of:
> 
> https://dri.freedesktop.org/docs/drm/gpu/drm-kms.html#overview
> 
> Plus everything that's getting linked from there ofc.
> 
>>> -
>>> -CRTC Initialization
>>> -~~~~~~~~~~~~~~~~~~~
>>> -
>>> -A KMS device must create and register at least one struct
>>> -:c:type:`struct drm_crtc <drm_crtc>` instance. The instance is
>>> -allocated and zeroed by the driver, possibly as part of a larger
>>> -structure, and registered with a call to :c:func:`drm_crtc_init()`
>>> -with a pointer to CRTC functions.
>>> -
>>> -
>>> -Cleanup
>>> --------
>>> -
>>> -The DRM core manages its objects' lifetime. When an object is not needed
>>> -anymore the core calls its destroy function, which must clean up and
>>> -free every resource allocated for the object. Every
>>> -:c:func:`drm_\*_init()` call must be matched with a corresponding
>>> -:c:func:`drm_\*_cleanup()` call to cleanup CRTCs
>>> -(:c:func:`drm_crtc_cleanup()`), planes
>>> -(:c:func:`drm_plane_cleanup()`), encoders
>>> -(:c:func:`drm_encoder_cleanup()`) and connectors
>>> -(:c:func:`drm_connector_cleanup()`). Furthermore, connectors that
>>> -have been added to sysfs must be removed by a call to
>>> -:c:func:`drm_connector_unregister()` before calling
>>> -:c:func:`drm_connector_cleanup()`.
>>> -
>>> -Connectors state change detection must be cleanup up with a call to
>>> -:c:func:`drm_kms_helper_poll_fini()`.
>>> -
>>> -Output discovery and initialization example
>>> --------------------------------------------
>>> -
>>> -.. code-block:: c
>>> -
>>> -    void intel_crt_init(struct drm_device *dev)
>>> -    {
>>> -        struct drm_connector *connector;
>>> -        struct intel_output *intel_output;
>>> -
>>> -        intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL);
>>> -        if (!intel_output)
>>> -            return;
>>> -
>>> -        connector = &intel_output->base;
>>> -        drm_connector_init(dev, &intel_output->base,
>>> -                   &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA);
>>> -
>>> -        drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs,
>>> -                 DRM_MODE_ENCODER_DAC);
>>> -
>>> -        drm_connector_attach_encoder(&intel_output->base,
>>> -                          &intel_output->enc);
>>> -
>>> -        /* Set up the DDC bus. */
>>> -        intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A");
>>> -        if (!intel_output->ddc_bus) {
>>> -            dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration "
>>> -                   "failed.\n");
>>> -            return;
>>> -        }
>>> -
>>> -        intel_output->type = INTEL_OUTPUT_ANALOG;
>>> -        connector->interlace_allowed = 0;
>>> -        connector->doublescan_allowed = 0;
>>> -
>>> -        drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs);
>>> -        drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs);
>>> -
>>> -        drm_connector_register(connector);
>>> -    }
>>> -
>>> -In the example above (taken from the i915 driver), a CRTC, connector and
>>> -encoder combination is created. A device-specific i2c bus is also
>>> -created for fetching EDID data and performing monitor detection. Once
>>> -the process is complete, the new connector is registered with sysfs to
>>> -make its properties available to applications.
>>> -
>>>    KMS Locking
>>>    ===========
>>>    
>>>
>>
>> Everything else looks fine to drop.
>>
>> The bits about initialization/cleanup/subclassing/connectors can all be
>> found in the Atomic Mode Setting section or one of the abstraction sections.
> 
> With the one thing you wanted to keep also wrong - ok with this patch?
> 
> Thanks for taking a look at this.
> -Daniel
> 

Sounds good.

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>

Nicholas Kazlauskas