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

[Daniel Vetter]

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
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch