Media +Driver Guide

Issues to consider

The main issue to consider when +writing a media device driver for a writable demand paging environment is +to avoid page faults from occurring in DFCs, since this can lead to a deadlock +condition between the driver and the client process.

This can be avoided +using the following methods:

Use shared chunks.

Shared +chunks are memory areas that are accessible by both kernel-side and user-side +and they are never paged.

This is the best solution for drivers that +involve fast throughput such as media drivers.
Use synchronous rather +than asynchronous data transfer

This could be done by implementing +the following steps:
1. The client requests +a notification when data is available.
2. The data arrives.
3. The driver writes data +into an internal buffer and completes the client request.
4. The client makes a read +request.
5. The driver writes the +data back to the client in the client thread context.
This approach is easy to implement, however it requires the buffering +of data.
Use the flexible +memory model

This provides the ability for the memory to be +mapped into a drive's address space as unpaged.

This is an alternative +to the use of shared chunks.

However, this is not supported on the +moving or multiple memory models.