对Midlayer mistake的理解

http://lwn.net/Articles/336262/

Library  versus midlayer

Library:

1. a clean interface to upper layer

2. speerate implementation fo each different bottom drivers

3. Drivers can use  different lib-supported operations to realize its function

Midlayer:

1. a clean interface to upper layer

2. impose specific sequence of operations in midlayer

3. clean interface to bottom layer

4. supposedly to ease bottom driver writiing

4. midlyaer may become too complex when adding more special cases