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.