Kernel clients¶

This library provides support for clients running in the kernel like fbdev and bootsplash.

GEM drivers which provide a GEM based dumb buffer with a virtual address are supported.

struct drm_client_funcs¶: DRM client callbacks

Definition:

struct drm_client_funcs {
    struct module *owner;
    void (*unregister)(struct drm_client_dev *client);
    int (*restore)(struct drm_client_dev *client);
    int (*hotplug)(struct drm_client_dev *client);
    int (*suspend)(struct drm_client_dev *client, bool holds_console_lock);
    int (*resume)(struct drm_client_dev *client, bool holds_console_lock);
};

Members

owner

The module owner

unregister

Called when drm_device is unregistered. The client should respond by releasing its resources using drm_client_release().

This callback is optional.

restore

Called on drm_lastclose(). The first client instance in the list that returns zero gets the privilege to restore and no more clients are called. This callback is not called after unregister has been called.

Note that the core does not guarantee exclusion against concurrent drm_open(). Clients need to ensure this themselves, for example by using drm_master_internal_acquire() and drm_master_internal_release().

This callback is optional.

hotplug

Called on drm_kms_helper_hotplug_event(). This callback is not called after unregister has been called.

This callback is optional.

suspend

Called when suspending the device.

This callback is optional.

FIXME: Some callers hold the console lock when invoking this: function. This interferes with fbdev emulation, which also tries to acquire the lock. Push the console lock into the callback and remove ‘holds_console_lock’.

resume

Called when resuming the device from suspend.

This callback is optional.

FIXME: Some callers hold the console lock when invoking this: function. This interferes with fbdev emulation, which also tries to acquire the lock. Push the console lock into the callback and remove ‘holds_console_lock’.

struct drm_client_dev¶: DRM client instance

Definition:

struct drm_client_dev {
    struct drm_device *dev;
    const char *name;
    struct list_head list;
    const struct drm_client_funcs *funcs;
    struct drm_file *file;
    struct mutex modeset_mutex;
    struct drm_mode_set *modesets;
    bool suspended;
    bool hotplug_failed;
};

Members

dev: DRM device
name: Name of the client.
list: List of all clients of a DRM device, linked into drm_device.clientlist. Protected by drm_device.clientlist_mutex.
funcs: DRM client functions (optional)
file: DRM file
modeset_mutex: Protects modesets.
modesets: CRTC configurations
suspended: The client has been suspended.
hotplug_failed: Set by client hotplug helpers if the hotplugging failed before. It is usually not tried again.

struct drm_client_buffer¶: DRM client buffer

Definition:

struct drm_client_buffer {
    struct drm_client_dev *client;
    u32 pitch;
    struct drm_gem_object *gem;
    struct iosys_map map;
    struct drm_framebuffer *fb;
};

Members

client

DRM client

pitch

Buffer pitch

gem

GEM object backing this buffer

FIXME: The dependency on GEM here isn’t required, we could convert the driver handle to a dma-buf instead and use the backend-agnostic dma-buf vmap support instead. This would require that the handle2fd prime ioctl is reworked to pull the fd_install step out of the driver backend hooks, to make that final step optional for internal users.

map

Virtual address for the buffer

fb

DRM framebuffer

drm_client_for_each_modeset¶

drm_client_for_each_modeset (modeset, client)

Iterate over client modesets

Parameters

modeset: drm_mode_set loop cursor
client: DRM client

drm_client_for_each_connector_iter¶

drm_client_for_each_connector_iter (connector, iter)

connector_list iterator macro

Parameters

connector: struct drm_connector pointer used as cursor
iter: struct drm_connector_list_iter

Description

This iterates the connectors that are useable for internal clients (excludes writeback connectors).

For more info see drm_for_each_connector_iter().

int drm_client_init(struct drm_device *dev, struct drm_client_dev *client, const char *name, const struct drm_client_funcs *funcs)¶: Initialise a DRM client

Parameters

struct drm_device *dev: DRM device
struct drm_client_dev *client: DRM client
const char *name: Client name
const struct drm_client_funcs *funcs: DRM client functions (optional)

Description

This initialises the client and opens a drm_file. Use drm_client_register() to complete the process. The caller needs to hold a reference on dev before calling this function. The client is freed when the drm_device is unregistered. See drm_client_release().

Return

Zero on success or negative error code on failure.

void drm_client_register(struct drm_client_dev *client)¶: Register client

Parameters

struct drm_client_dev *client: DRM client

Description

Add the client to the drm_device client list to activate its callbacks. client must be initialized by a call to drm_client_init(). After drm_client_register() it is no longer permissible to call drm_client_release() directly (outside the unregister callback), instead cleanup will happen automatically on driver unload.

Registering a client generates a hotplug event that allows the client to set up its display from pre-existing outputs. The client must have initialized its state to able to handle the hotplug event successfully.

void drm_client_release(struct drm_client_dev *client)¶: Release DRM client resources

Parameters

struct drm_client_dev *client: DRM client

Description

Releases resources by closing the drm_file that was opened by drm_client_init(). It is called automatically if the drm_client_funcs.unregister callback is _not_ set.

This function should only be called from the unregister callback. An exception is fbdev which cannot free the buffer if userspace has open file descriptors.

Note

Clients cannot initiate a release by themselves. This is done to keep the code simple. The driver has to be unloaded before the client can be unloaded.

int drm_client_buffer_vmap_local(struct drm_client_buffer *buffer, struct iosys_map *map_copy)¶: Map DRM client buffer into address space

Parameters

struct drm_client_buffer *buffer: DRM client buffer
struct iosys_map *map_copy: Returns the mapped memory’s address

Description

This function maps a client buffer into kernel address space. If the buffer is already mapped, it returns the existing mapping’s address.

Client buffer mappings are not ref’counted. Each call to drm_client_buffer_vmap_local() should be closely followed by a call to drm_client_buffer_vunmap_local(). See drm_client_buffer_vmap() for long-term mappings.

The returned address is a copy of the internal value. In contrast to other vmap interfaces, you don’t need it for the client’s vunmap function. So you can modify it at will during blit and draw operations.

Return

0 on success, or a negative errno code otherwise.

void drm_client_buffer_vunmap_local(struct drm_client_buffer *buffer)¶: Unmap DRM client buffer

Parameters

struct drm_client_buffer *buffer: DRM client buffer

Description

This function removes a client buffer’s memory mapping established with drm_client_buffer_vunmap_local(). Calling this function is only required by clients that manage their buffer mappings by themselves.

int drm_client_buffer_vmap(struct drm_client_buffer *buffer, struct iosys_map *map_copy)¶: Map DRM client buffer into address space

Parameters

struct drm_client_buffer *buffer: DRM client buffer
struct iosys_map *map_copy: Returns the mapped memory’s address

Description

This function maps a client buffer into kernel address space. If the buffer is already mapped, it returns the existing mapping’s address.

Client buffer mappings are not ref’counted. Each call to drm_client_buffer_vmap() should be followed by a call to drm_client_buffer_vunmap(); or the client buffer should be mapped throughout its lifetime.

The returned address is a copy of the internal value. In contrast to other vmap interfaces, you don’t need it for the client’s vunmap function. So you can modify it at will during blit and draw operations.

Return

0 on success, or a negative errno code otherwise.

void drm_client_buffer_vunmap(struct drm_client_buffer *buffer)¶: Unmap DRM client buffer

Parameters

struct drm_client_buffer *buffer: DRM client buffer

Description

This function removes a client buffer’s memory mapping. Calling this function is only required by clients that manage their buffer mappings by themselves.

struct drm_client_buffer *drm_client_framebuffer_create(struct drm_client_dev *client, u32 width, u32 height, u32 format)¶: Create a client framebuffer

Parameters

struct drm_client_dev *client: DRM client
u32 width: Framebuffer width
u32 height: Framebuffer height
u32 format: Buffer format

Description

This function creates a drm_client_buffer which consists of a drm_framebuffer backed by a dumb buffer. Call drm_client_framebuffer_delete() to free the buffer.

Return

Pointer to a client buffer or an error pointer on failure.

void drm_client_framebuffer_delete(struct drm_client_buffer *buffer)¶: Delete a client framebuffer

Parameters

struct drm_client_buffer *buffer: DRM client buffer (can be NULL)

int drm_client_framebuffer_flush(struct drm_client_buffer *buffer, struct drm_rect *rect)¶: Manually flush client framebuffer

Parameters

struct drm_client_buffer *buffer: DRM client buffer (can be NULL)
struct drm_rect *rect: Damage rectangle (if NULL flushes all)

Description

This calls drm_framebuffer_funcs->dirty (if present) to flush buffer changes for drivers that need it.

Return

Zero on success or negative error code on failure.

int drm_client_modeset_probe(struct drm_client_dev *client, unsigned int width, unsigned int height)¶: Probe for displays

Parameters

struct drm_client_dev *client: DRM client
unsigned int width: Maximum display mode width (optional)
unsigned int height: Maximum display mode height (optional)

Description

This function sets up display pipelines for enabled connectors and stores the config in the client’s modeset array.

Return

Zero on success or negative error code on failure.

bool drm_client_rotation(struct drm_mode_set *modeset, unsigned int *rotation)¶: Check the initial rotation value

Parameters

struct drm_mode_set *modeset: DRM modeset
unsigned int *rotation: Returned rotation value

Description

This function checks if the primary plane in modeset can hw rotate to match the rotation needed on its connector.

Note

Currently only 0 and 180 degrees are supported.

Return

True if the plane can do the rotation, false otherwise.

int drm_client_modeset_check(struct drm_client_dev *client)¶: Check modeset configuration

Parameters

struct drm_client_dev *client: DRM client

Description

Check modeset configuration.

Return

Zero on success or negative error code on failure.

int drm_client_modeset_commit_locked(struct drm_client_dev *client)¶: Force commit CRTC configuration

Parameters

struct drm_client_dev *client: DRM client

Description

Commit modeset configuration to crtcs without checking if there is a DRM master. The assumption is that the caller already holds an internal DRM master reference acquired with drm_master_internal_acquire().

Return

Zero on success or negative error code on failure.

int drm_client_modeset_commit(struct drm_client_dev *client)¶: Commit CRTC configuration

Parameters

struct drm_client_dev *client: DRM client

Description

Commit modeset configuration to crtcs.

Return

Zero on success or negative error code on failure.

int drm_client_modeset_dpms(struct drm_client_dev *client, int mode)¶: Set DPMS mode

Parameters

struct drm_client_dev *client: DRM client
int mode: DPMS mode

Note

For atomic drivers mode is reduced to on/off.

Return

Zero on success or negative error code on failure.

void drm_client_dev_unregister(struct drm_device *dev)¶: Unregister clients

Parameters

struct drm_device *dev: DRM device

Description

This function releases all clients by calling each client’s drm_client_funcs.unregister callback. The callback function is responsibe for releaseing all resources including the client itself.

The helper drm_dev_unregister() calls this function. Drivers that use it don’t need to call this function themselves.

void drm_client_dev_hotplug(struct drm_device *dev)¶: Send hotplug event to clients

Parameters

struct drm_device *dev: DRM device

Description

This function calls the drm_client_funcs.hotplug callback on the attached clients.

drm_kms_helper_hotplug_event() calls this function, so drivers that use it don’t need to call this function themselves.

The Linux Kernel

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Kernel clients¶