Kernel-Side Services

This section describes how device drivers can use the services that the Kernel provides.

The section begins with a discussion of the APIs for fundamental types such as buffers and arrays. Kernel side programs cannot use all of the same APIs as user-side programs, so you need to be aware of these restrictions, and the alternative APIs provided by the Kernel.

The guide then discusses a number of idioms for communicating between different threads and processes, including Publish and Subscribe, Kernel-side messages, shared chunks, and environment slots.

Some more advanced programming issues are then discussed, including how to design a device driver to behave correctly in a demand paged OS environment, in which client programs may not be continuously in memory, and how to integrate a device driver with system wide power resource management.

The section ends with a discussion of how Kernel APIs encourage safe programming with the use of precondition checks.

• Basic APIs
  Accessing APIs and basic functions in kernel-side programs.
• Thread Synchronisation
  Kernel-side techniques to protect critical regions in code or to allow safe access to shared data.
• Thread Termination
  This topic describes how and in what conditions to kill a kernel side thread.
• Publish and Subscribe
  Publish and Subscribe allows global variables to be set and retrieved, and allows subscribers to be notified that variables have changed.
• Kernel-side Messages
  Kernel-side messages are a means of communication between Symbian platform threads executing kernel-side code.
• Shared Chunks
  A shared chunk is a mechanism that kernel-side code uses to share memory buffers safely with user-side code.
• Environment Slots
  Up to 16 separate pieces of information can be passed to a process on creation using Environment Slots. These include handles and binary data.
• Power Resource Manager (PRM)
  Describes the Power Resource Manager.
• Physical RAM Defragmentation
  Describes Symbian platform RAM defragmentation.
• Vector Floating Point Architecture (VFP)
  Describes the implementation of the ARM Vector Floating Point Architecture (VFPv2) on Symbian platform.
• Level 2 Cache
  Level 2 cache is cache memory that is external to the microprocessor. The kernel provides functions to perform operations on this cache.
• Remapping Cache Attributes and Access Permissions on ARMv6K and ARMv7 Platforms
  Describes the behavior change brought about by remapping the cache attributes and the access permissions on the ARMv6K (ARM1176 & ARM11MPCore), ARMv7 (Cortex-8N), and future platforms.
• Kernel API Validity Checks
  Describes the pre-condition checks that Kernel APIs can do when they are called.
• Pre-Conditions and Post-Conditions for Kernel APIs
  Reference documentation for kernel side function APIs, specifies a wide variety of pre-conditions and post-conditions.
• Performance Logging
  Symbian platform provides macros that you can use in device driver and kernel extension programs to write a trace log.