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drm/doc: Drop chapter "KMS Initialization and Cleanup"

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It only talks about crtc, brings up intel as an example and I think is
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.

v2: Fix typo in commit message (Nicholas).

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190130163006.28945-2-daniel.vetter@ffwll.ch
This commit is contained in:
Daniel Vetter 2019-01-30 17:30:05 +01:00
parent 5d0aa37855
commit d9f7bb56c2
1 changed files with 0 additions and 96 deletions
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Documentation/gpu/drm-kms.rst
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@ -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.
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
===========