LddDriverModelIntro < Training2

%SECTION0{name=LddDriverModelIntro}% Driver model and sysfs

   * motivation (state pre 2.5): 
      * no uniform, comprehensive model, only bus specific lists of devices
      * =procfs= was getting messy (large files, not hierarchy)
      * more and more hotpluggable devices
      * generic power and shutdown management impossible

   * solution: _driver model_
      * introduced in 2.5, evolved a lot!
      * uniform model for representing busses, devices and drivers as a hierarchy

   * sysfs
      * often confused with driver model
      * special file system that exports hierarchical view of all the devices in the system
      * driver model can exist without sysfs, but sysfs not without driver model

   * Characteristics:
      * discoverable (device classes)
      * how interconnected?
      * cleaner: one value per sysfs file
      * handles reference counting
      * generic hotplug support

   * The driver model is _very_ complex, but fortunately the kernel does most work for us


*example*

<verbatim>
$ tree -L 1  /sys/
/sys/
|-- block
|-- bus
|-- class
|-- devices
|-- firmware
|-- fs
|-- kernel
|-- module
`-- power
</verbatim>

explore with =tree(1)=
5.5. The Linux driver model		1. Denx Training Topics		5.5.2. How does it all fit together?
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