[PATCH v2] drm/vkms: Add documentation
Louis Chauvet
louis.chauvet at bootlin.com
Mon Aug 26 16:22:45 UTC 2024
Add documentation around vkms_output and its initialization.
Signed-off-by: Louis Chauvet <louis.chauvet at bootlin.com>
---
This series does not introduce functionnal changes, only some
documentation and renaming to clarify the code.
---
Changes in v2:
- Dropped already applied patches
- Dropped useless patch as its content is deleted later
- Remove dependency on previous series
- Apply Maíra's comments
- Link to v1: https://lore.kernel.org/r/20240814-google-clarifications-v1-0-3ee76d7d0c28@bootlin.com
---
drivers/gpu/drm/vkms/vkms_drv.h | 86 ++++++++++++++++++++++++++++++++------
drivers/gpu/drm/vkms/vkms_output.c | 12 ++++++
2 files changed, 86 insertions(+), 12 deletions(-)
diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index 5e46ea5b96dc..1fc068d4de4c 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -73,29 +73,56 @@ struct vkms_color_lut {
};
/**
- * vkms_crtc_state - Driver specific CRTC state
+ * struct vkms_crtc_state - Driver specific CRTC state
+ *
* @base: base CRTC state
* @composer_work: work struct to compose and add CRC entries
- * @n_frame_start: start frame number for computed CRC
- * @n_frame_end: end frame number for computed CRC
+ *
+ * @num_active_planes: Number of active planes
+ * @active_planes: List containing all the active planes (counted by
+ * @num_active_planes). They should be stored in z-order.
+ * @active_writeback: Current active writeback job
+ * @gamma_lut: Look up table for gamma used in this CRTC
+ * @crc_pending: Protected by @vkms_output.composer_lock, true when the frame CRC is not computed
+ * yet. Used by vblank to detect if the composer is too slow.
+ * @wb_pending: Protected by @vkms_output.composer_lock, true when a writeback frame is requested.
+ * @frame_start: Protected by @vkms_output.composer_lock, saves the frame number before the start
+ * of the composition process.
+ * @frame_end: Protected by @vkms_output.composer_lock, saves the last requested frame number.
+ * This is used to generate enough CRC entries when the composition worker is too slow.
*/
struct vkms_crtc_state {
struct drm_crtc_state base;
struct work_struct composer_work;
int num_active_planes;
- /* stack of active planes for crc computation, should be in z order */
struct vkms_plane_state **active_planes;
struct vkms_writeback_job *active_writeback;
struct vkms_color_lut gamma_lut;
- /* below four are protected by vkms_output.composer_lock */
bool crc_pending;
bool wb_pending;
u64 frame_start;
u64 frame_end;
};
+/**
+ * struct vkms_output - Internal representation of all output components in vkms
+ *
+ * @crtc: Base CRTC in DRM
+ * @encoder: DRM encoder used for this output
+ * @connector: DRM connector used for this output
+ * @wb_connecter: DRM writeback connector used for this output
+ * @vblank_hrtimer: Timer used to trigger the vblank
+ * @period_ns: Period of the vblank timer, used to configure @vblank_hrtimer and to compute
+ * vblank timestamps
+ * @composer_workq: Ordered workqueue for @composer_state.composer_work.
+ * @lock: Lock used to protect concurrent access to the composer
+ * @composer_enabled: Protected by @lock, true when the vkms composer is active (crc needed or
+ * writeback)
+ * @composer_state: Current state of this vkms output
+ * @composer_lock: Lock used internally to protect @composer_state members
+ */
struct vkms_output {
struct drm_crtc crtc;
struct drm_encoder encoder;
@@ -103,28 +130,38 @@ struct vkms_output {
struct drm_writeback_connector wb_connector;
struct hrtimer vblank_hrtimer;
ktime_t period_ns;
- /* ordered wq for composer_work */
struct workqueue_struct *composer_workq;
- /* protects concurrent access to composer */
spinlock_t lock;
- /* protected by @lock */
bool composer_enabled;
struct vkms_crtc_state *composer_state;
spinlock_t composer_lock;
};
-struct vkms_device;
-
+/**
+ * struct vkms_config - General configuration for VKMS driver
+ *
+ * @writeback: If true, a writeback buffer can be attached to the CRTC
+ * @cursor: If true, a cursor plane is created in the VKMS device
+ * @overlay: If true, NUM_OVERLAY_PLANES will be created for the VKMS device
+ * @dev: Used to store the current vkms device. Only set when the device is instantiated.
+ */
struct vkms_config {
bool writeback;
bool cursor;
bool overlay;
- /* only set when instantiated */
struct vkms_device *dev;
};
+/**
+ * struct vkms_device - Description of a vkms device
+ *
+ * @drm - Base device in DRM
+ * @platform - Associated platform device
+ * @output - Configuration and sub-components of the vkms device
+ * @config: Configuration used in this vkms device
+ */
struct vkms_device {
struct drm_device drm;
struct platform_device *platform;
@@ -132,6 +169,10 @@ struct vkms_device {
const struct vkms_config *config;
};
+/*
+ * The following helpers are used to convert a member of a struct into its parent.
+ */
+
#define drm_crtc_to_vkms_output(target) \
container_of(target, struct vkms_output, crtc)
@@ -144,12 +185,33 @@ struct vkms_device {
#define to_vkms_plane_state(target)\
container_of(target, struct vkms_plane_state, base.base)
-/* CRTC */
+/**
+ * vkms_crtc_init() - Initialize a CRTC for vkms
+ * @dev: DRM device associated with the vkms buffer
+ * @crtc: uninitialized CRTC device
+ * @primary: primary plane to attach to the CRTC
+ * @cursor plane to attach to the CRTC
+ */
int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
struct drm_plane *primary, struct drm_plane *cursor);
+/**
+ * vkms_output_init() - Initialize all sub-components needed for a vkms device.
+ *
+ * @vkmsdev: vkms device to initialize
+ * @possible_crtc_index: CRTC which can be attached to the planes. The caller must ensure that
+ * possible_crtc_index is positive and less or equals to 31.
+ */
int vkms_output_init(struct vkms_device *vkmsdev, int index);
+/**
+ * vkms_plane_init() - Initialize a plane
+ *
+ * @vkmsdev: vkms device containing the plane
+ * @type: type of plane to initialize
+ * @possible_crtc_index: CRTC which can be attached to the plane. The caller must ensure that
+ * possible_crtc_index is positive and less or equals to 31.
+ */
struct vkms_plane *vkms_plane_init(struct vkms_device *vkmsdev,
enum drm_plane_type type, int index);
diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
index 5ce70dd946aa..da69beb43ab0 100644
--- a/drivers/gpu/drm/vkms/vkms_output.c
+++ b/drivers/gpu/drm/vkms/vkms_output.c
@@ -21,6 +21,7 @@ static int vkms_conn_get_modes(struct drm_connector *connector)
{
int count;
+ /* Use the default modes list from DRM */
count = drm_add_modes_noedid(connector, XRES_MAX, YRES_MAX);
drm_set_preferred_mode(connector, XRES_DEF, YRES_DEF);
@@ -58,6 +59,12 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
int writeback;
unsigned int n;
+ /*
+ * Initialize used plane. One primary plane is required to perform the composition.
+ *
+ * The overlay and cursor planes are not mandatory, but can be used to perform complex
+ * composition.
+ */
primary = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_PRIMARY, index);
if (IS_ERR(primary))
return PTR_ERR(primary);
@@ -76,6 +83,7 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
return PTR_ERR(cursor);
}
+ /* [1]: Allocation of a CRTC, its index will be 1 */
ret = vkms_crtc_init(dev, crtc, &primary->base, &cursor->base);
if (ret)
return ret;
@@ -95,6 +103,10 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
DRM_ERROR("Failed to init encoder\n");
goto err_encoder;
}
+ /*
+ * This is an hardcoded value to select crtc for the encoder.
+ * 1 here designate the first registered CRTC, the one allocated in [1]
+ */
encoder->possible_crtcs = 1;
ret = drm_connector_attach_encoder(connector, encoder);
---
base-commit: 22bc22ccf95bfa6eb6288ba4bc33d7fc0078381e
change-id: 20240520-google-clarifications-dede8dcbe38a
Best regards,
--
Louis Chauvet <louis.chauvet at bootlin.com>
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