forked from KolibriOS/kolibrios
249 lines
12 KiB
Plaintext
249 lines
12 KiB
Plaintext
Last edit: 26/07/2013
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Kernel event subsystem may be useful when writing drivers and kernel space
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services. It is not related to the subsystem of GUI events. An event, from the
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kernel's point of view, is a kernel space object which is owned by the thread
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that created it.
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struc EVENT
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{
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.magic dd ? ; 'EVNT'
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.destroy dd ? ; internal destructor
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.fd dd ? ; next object in list
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.bk dd ? ; prev object in list
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.pid dd ? ; owner (thread) id
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.id dd ? ; event uid. (just a number)
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.state dd ? ; internal flags; see below
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.code dd ? ; MSB: event class; next byte: priority
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; (used by kernel only, always 0 for reading),
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; The higher dword value the higher event priority.
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; Two LSBs: event code.
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rd 5 ; .data: the structure of this field is not defined and
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; depends on .code field. (Pass any data you need here)
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.size = $ - .magic
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.codesize = $ - .code
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}
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Realtime events have class 0хFF. Currently defined:
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EVENT.code= ; (Used in sound subsystem)
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RT_INP_EMPTY = 0xFF000001
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RT_OUT_EMPTY = 0xFF000002
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RT_INP_FULL = 0xFF000003
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RT_OUT_FULL = 0xFF000004
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Flags of EVENT.state field are defined in gui/event.inc.
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EVENT_SIGNALED = 0x20000000 ; bit 29: event is active/inactive
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EVENT_WATCHED = 0x10000000 ; bit 28: owner thread is waiting for the
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; event to be active
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MANUAL_RESET = 0x40000000 ; bit 30: do not deactivate event
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: automatically on receive
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MANUAL_DESTROY = 0x80000000 ; bit 31: do not return event to a list of
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; free ones on receive
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As of SVN r3732 (assume same below) the definition is located in
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/kernel/trunk/const.inc and is as follows:
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struct APPOBJ ; common object header
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magic dd ? ;
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destroy dd ? ; internal destructor
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fd dd ? ; next object in list
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bk dd ? ; prev object in list
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pid dd ? ; owner id
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ends
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struct EVENT APPOBJ
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id dd ? ; event uid
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state dd ? ; internal flags
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code dd ?
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rd 5 ; .data
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ends
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Code is located in gui/event.inc.
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Event objects live in kernel memory as a double-linked list (see fields .bk and
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.fd). While initialization the kernel reserves memory, creates 512 events and
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places them into FreeEvents list. When out of free event, kernel creates another
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512 ones etc. Each thread has own double-linked lists where an event may be
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placed to:
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ObjList -- a list of kernel objects associated with the thread;
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EventList -- a list of kernel events for the thread.
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When events are moved between lists or reordered their data are not copied. This
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is done only via modification of .fd and .bk fields. These lists work as FIFO
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queues. Sending does not block, receiving blocks. Addressing is direct, by
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thread id. There always is an owner thread for an event.
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Event's life cycle is defined by flags while creation. By default the kernel
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uses values MANUAL_RESET = 0 and MANUAL_DESTROY = 0. Such an event is oneshot
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and is automatically freed by the kernel and returned to the FreeEvents list
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when received. An event with flag MANUAL_DESTROY = 1 becomes inactive when
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received but remains in thread's object list and can be reused. An event with
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flags MANUAL_DESTROY = 1 and MANUAL_RESET = 1 remains active when received and
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can be reset via call to ClearEvent.
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A life cycle example of a sound subsystem event:
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* For an audio buffer (possibly several) the driver creates an event in ObjList
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by calling CreateEvent with flag MANUAL_DESTROY.
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* Then driver calls WaitEvent for the event (waits for EVENT_SIGNALED event
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flag) and blocks waiting for buffer update request.
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* The buffer update request is sent with RaiseEvent from another thread.
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* Sending (RaiseEvent) and receiving (WaitEvent) are repeated as buffer gets
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empty.
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* Driver deactivates the event with ClearEvent when playback is stopped.
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Actually, the event structure is described here only for understanding of
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subsystem work principles. Direct field access is discouraged due to possible
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compatibility issues in the future. Only API calls should be used. A pair
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"pointer to an event" and "event id" is considered a single 64-bit id. This id
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should be stored somewhere after a call to CreateEvent for further work with the
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event.
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The kernel exports following event related functions:
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(for drivers, etc; called from kernel mode)
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CreateEvent
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RaiseEvent
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ClearEvent
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SendEvent
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DestroyEvent
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WaitEvent
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WaitEventTimeout
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GetEvent
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For user applications sysfn 68.14 (a wrapper to GetEvent)
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--------------------------------------------------------------------------------
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CreateEvent:
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Creates a new event in ObjList queue of current thread.
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Sets:
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EVENT.destroy <= default internal destructor
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EVENT.pid <= current Process id
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EVENT.id <= unique id
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EVENT.state <= ecx: flags
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EVENT.code <= [esi]: size is 6*dword, do not copy if esi=0
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Returns:
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eax -- pointer to the event or 0 for error.
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edx -- Event.id.
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Destroys: eax,ebx,edx,ecx,esi,edi
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--------------------------------------------------------------------------------
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RaiseEvent:
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Activates existing event (may be owned by another thread) by setting
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EVENT_SIGNALED flag. Sets EVENT.code data if necessary. Does nothing
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more if EVENT_SIGNALED flag is already active in the event. If
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EVENT_SIGNALED flag is not set in the event it will be set, except when
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EVENT_WATCHED in edx = 1 and EVENT_WATCHED in the event = 0. I.e. while
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setting EVENT_WATCHED in edx it is checked if owner thread is waiting
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for event activation. No flags, except EVENT_SIGNALED, are modified in
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the event.
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Gets:
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eax -- pointer to event
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ebx -- id
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edx -- flags (see EVENT.state)
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Sets:
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EVENT.code <= [esi]: size is 6*dword, do not copy if esi=0
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Returns: ?
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Destroys: eax,ebx,edx,ecx,esi,edi
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--------------------------------------------------------------------------------
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ClearEvent:
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Move event to ObjList of owner thread. (May be it was already there.)
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Reset flags EVENT_SIGNALED and EVENT_WATCHED, keep other fields (.code,
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.id).
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Gets:
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eax -- pointer to event
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ebx -- id
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Returns: ?
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Destroys: eax,ebx,ecx,edi
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--------------------------------------------------------------------------------
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SendEvent:
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Create a new event in the event list of target thread. Sets
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EVENT_SIGNALED flag in the event.
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Gets:
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EVENT.pid <= eax: target thread id;
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EVENT.code <= [esi]: size is 6*dword, do not copy if esi=0
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Returns:
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eax -- pointer to event or 0 for error
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edx -- Event.id
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Destroys: eax,ebx,ecx,esi,edi
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--------------------------------------------------------------------------------
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DestroyEvent:
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Moves event to FreeEvents, clears fields .magic, .destroy, .pid, .id.
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The event may be owned by other thread.
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Gets:
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eax -- pointer to event
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ebx -- event id
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Returns:
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eax -- 0 for error, non-zero for success
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Destroy: eax,ebx,ecx
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--------------------------------------------------------------------------------
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WaitEvent:
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Wait infinitely until flag EVENT_SIGNALED is set in the event owned by
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the caller thread. This flag is set by signaling thread via RaiseEvent.
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Waiting thread is frozen by setting TASKDATA.state <= TSTATE_WAITING=5.
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Flag EVENT_WATCHED is set in the event before freeze.
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If flag MANUAL_RESET is NOT set in the event then:
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EVENT_SIGNALED and EVENT_WATCHED are reset when the event is
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received.
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When MANUAL_DESTROY is
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inactive: the event is destroyed by DestroyEvent,
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active: the event is moved to ObjList of current thread.
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Gets:
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eax -- pointer to event
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ebx -- event id
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Returns: ?
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Destroys: eax,ebx,edx,ecx,esi,edi
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--------------------------------------------------------------------------------
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WaitEventTimeout:
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Wait with a timeout until flag EVENT_SIGNALED is set in the event owned
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by caller thread. This flag is set by signaling thread via RaiseEvent.
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Waiting thread is frozen by setting TASKDATA.state <= TSTATE_WAITING=5.
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Flag EVENT_WATCHED is set in the event before freeze.
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If flag MANUAL_RESET is NOT set in the event then:
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EVENT_SIGNALED and EVENT_WATCHED are reset when the event is
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received.
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When MANUAL_DESTROY is
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inactive: the event is destroyed by DestroyEvent,
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active: the event is moved to ObjList of current thread.
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Gets:
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eax -- pointer to event
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ebx -- event id
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ecx -- timeout, in ticks of system timer
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Returns:
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eax -- 0 if the event was not activated, or
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not 0 if activated
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Destroys: eax,ebx,edx,ecx,esi,edi
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--------------------------------------------------------------------------------
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GetEvent:
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Waits infinitely for any event in the queue of current thread. Thread is
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frozen by setting TASKDATA.state <= TSTATE_WAITING = 5. Event data
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(EVENT.code + 5*dword) are copied to specified buffer when received.
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Reset priority byte (see above) in the buffer.
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If flag MANUAL_RESET is NOT set in the event then:
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EVENT_SIGNALED and EVENT_WATCHED are reset when the event is
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received.
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When MANUAL_DESTROY is
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inactive: the event is destroyed by DestroyEvent,
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active: the event is moved to ObjList of current thread.
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Gets:
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edi -- pointer to buffer to copy data
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Returns:
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buffer with following data:
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+0: (EVENT.code) dword: id of following signal data
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+4: (EVENT.data) 5*dword: signal data, format depends on
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EVENT.code
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Destroys: eax,ebx,edx,ecx,esi,edi
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--------------------------------------------------------------------------------
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SysFn 68.14 for application: ; wrapped GetEvent
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Waits infinitely for any event in the queue of current thread. Thread is
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frozen by setting TASKDATA.state <= TSTATE_WAITING = 5. Event data
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(EVENT.code + 5*dword) are copied to specified buffer when received.
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Reset priority byte (see above) in the buffer.
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Gets:
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eax -- 68: function number
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ebx -- 14: subfunction number
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ecx -- pointer to data buffer (size is 6*dword)
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Returns:
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ecx = buffer with following data:
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+0: (EVENT.code) dword: id of following signal data
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+4: (EVENT.data) 5*dword: signal data, format depends on
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EVENT.code
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Destroys:
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eax
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