mirror of
https://github.com/zephyrproject-rtos/zephyr
synced 2025-09-03 14:01:55 +00:00
1964bf08bb
There are various situations where it's necessary to support turning devices on or off at runtime, includin power rails, clocks, other peripherals, and binary device power management. The complexity of properly managing multiple consumers of a device in a multithreaded system suggests that a shared implementation is desirable. This commit provides an API that supports managing on-off resources. Signed-off-by: Peter A. Bigot <pab@pabigot.com>
123 lines
4.3 KiB
ReStructuredText
123 lines
4.3 KiB
ReStructuredText
.. _kernel:
|
|
|
|
Kernel Services
|
|
###############
|
|
|
|
The Zephyr kernel lies at the heart of every Zephyr application. It provides
|
|
a low footprint, high performance, multi-threaded execution environment
|
|
with a rich set of available features. The rest of the Zephyr ecosystem,
|
|
including device drivers, networking stack, and application-specific code,
|
|
uses the kernel's features to create a complete application.
|
|
|
|
The configurable nature of the kernel allows you to incorporate only those
|
|
features needed by your application, making it ideal for systems with limited
|
|
amounts of memory (as little as 2 KB!) or with simple multi-threading
|
|
requirements (such as a set of interrupt handlers and a single background task).
|
|
Examples of such systems include: embedded sensor hubs, environmental sensors,
|
|
simple LED wearable, and store inventory tags.
|
|
|
|
Applications requiring more memory (50 to 900 KB), multiple communication
|
|
devices (like Wi-Fi and Bluetooth Low Energy), and complex multi-threading,
|
|
can also be developed using the Zephyr kernel. Examples of such systems
|
|
include: fitness wearables, smart watches, and IoT wireless gateways.
|
|
|
|
Scheduling, Interrupts, and Synchronization
|
|
*******************************************
|
|
|
|
These pages cover basic kernel services related to thread scheduling and
|
|
synchronization.
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
threads/index.rst
|
|
scheduling/index.rst
|
|
threads/system_threads.rst
|
|
threads/workqueue.rst
|
|
other/interrupts.rst
|
|
other/polling.rst
|
|
synchronization/semaphores.rst
|
|
synchronization/mutexes.rst
|
|
smp/smp.rst
|
|
|
|
Data Passing
|
|
************
|
|
|
|
These pages cover kernel objects which can be used to pass data between
|
|
threads and ISRs.
|
|
|
|
The following table summarizes their high-level features.
|
|
|
|
=============== ============== =================== ============== ============== ================= ============== ===============================
|
|
Object Bidirectional? Data structure Data item size Data Alignment ISRs can receive? ISRs can send? Overrun handling
|
|
=============== ============== =================== ============== ============== ================= ============== ===============================
|
|
FIFO No Queue Arbitrary [1] 4 B [2] Yes [3] Yes N/A
|
|
LIFO No Queue Arbitrary [1] 4 B [2] Yes [3] Yes N/A
|
|
Stack No Array Word Word Yes [3] Yes Undefined behavior
|
|
Message queue No Ring buffer Power of two Power of two Yes [3] Yes Pend thread or return -errno
|
|
Mailbox Yes Queue Arbitrary [1] Arbitrary No No N/A
|
|
Pipe No Ring buffer [4] Arbitrary Arbitrary No No Pend thread or return -errno
|
|
=============== ============== =================== ============== ============== ================= ============== ===============================
|
|
|
|
[1] Callers allocate space for queue overhead in the data
|
|
elements themselves.
|
|
|
|
[2] Objects added with k_fifo_alloc_put() and k_lifo_alloc_put()
|
|
do not have alignment constraints, but use temporary memory from the
|
|
calling thread's resource pool.
|
|
|
|
[3] ISRs can receive only when passing K_NO_WAIT as the timeout
|
|
argument.
|
|
|
|
[4] Optional.
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
data_passing/fifos.rst
|
|
data_passing/lifos.rst
|
|
data_passing/stacks.rst
|
|
data_passing/message_queues.rst
|
|
data_passing/mailboxes.rst
|
|
data_passing/pipes.rst
|
|
|
|
Memory Management
|
|
*****************
|
|
|
|
These pages cover memory allocation and management services.
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
memory/slabs.rst
|
|
memory/pools.rst
|
|
memory/heap.rst
|
|
|
|
Timing
|
|
******
|
|
|
|
These pages cover timing related services.
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
timing/clocks.rst
|
|
timing/timers.rst
|
|
|
|
Other
|
|
*****
|
|
|
|
These pages cover other kernel services.
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
other/cpu_idle.rst
|
|
other/atomic.rst
|
|
other/float.rst
|
|
other/ring_buffers.rst
|
|
other/resource_mgmt.rst
|
|
other/cxx_support.rst
|
|
other/version.rst
|
|
other/fatal.rst
|