Port client drivers to use the PRM

Purpose

Device drivers must register as clients to access services of the PRM.

Introduction

Kernel side components can access PRM services through exported kernel side APIs by including resourceman.h and linking against the static library provided by the PRM. See setup and configuration requirements.

Porting client drivers

Kernel side components register as clients with the PRM from their entry point during kernel boot and device drivers register as clients on channel opening.

User side components can access PRM services through a user side proxy interface. See user-side for more information.

To guarantee deterministic behaviour during resource state change and read operations (mainly on a long latency resource), clients should pre-allocate ‘client level’ objects and request objects using AllocReserve(). This needs to be done immediately after registering as clients of the PRM.

Before de-registering as clients from PRM, device drivers must:

• Cancel any pending asynchronous request with CancelAsyncRequestCallback(). If CancelAsyncRequestCallback returns KErrInUse the client must wait for the request to complete before proceeding with deregistration as the asynchronous request has started processing and will run to completion,

• Cancel all resource state change notification requests issued by this client using CancelNotification(),

• Delete the asynchronous callback objects and notification objects created by this client to avoid memory leak.

Omissions

PRM APIs cannot be called from a Null thread, ISR or from DFC thread1. However it might be possible that ISR need to operate on a power resource, for example, a power supply may need to be turned on before a hardware register that an ISR is interested on can be read. In this case Base port developers need to access the power resource directly. In order for the PRM to provide a consistent view of power resources any resource manipulators in an ISR must leave them unchanged, so in the above example, the ISR must turn OFF the power supply after it read the registers.