Add a page on devices
diff --git a/_data/documentation.yml b/_data/documentation.yml
index 2b006e7..ac2234d 100644
--- a/_data/documentation.yml
+++ b/_data/documentation.yml
@@ -81,11 +81,11 @@
- title: Full System
- id: fullsystem
- url: /documentation/general_docs/fullsystem
- subitems:
- - page: Creating Disk Images
+ items:
+ - title: Creating Disk Images
url: /documentation/general_docs/fullsystem/disks
+ - title: Devices
+ url: /documentation/general_docs/fullsystem/devices
- title: Memory System
items:
diff --git a/_pages/documentation/general_docs/fullsystem/devices.md b/_pages/documentation/general_docs/fullsystem/devices.md
new file mode 100644
index 0000000..53f2aee
--- /dev/null
+++ b/_pages/documentation/general_docs/fullsystem/devices.md
@@ -0,0 +1,64 @@
+---
+layout: documentation
+title: Devices
+parent: documentation
+permalink: documentation/general_docs/fullsystem/devices
+---
+
+# Devices in full system mode
+
+## I/O Device Base Classes
+
+The base classes in src/dev/\*_device.\* allow devices to be created with reasonable ease.
+The classes and virtual functions that must be implemented are listed below.
+Before reading the following it will help to be familiar with the [Memory_System](../memory_system).
+
+### PioPort
+
+The PioPort class is a programmed I/O port that all devices that are sensitive to an address range use.
+The port takes all the memory access types and roles them into one `read()` and `write()` call that the device must respond to.
+The device must also provide the `addressRanges()` function with which it returns the address ranges it is interested in.
+If desired a device could have more than one PIO port.
+However in the normal case it would only have one port and return multiple ranges when the `addressRange()` function is called. The only time multiple PIO ports would be desirable is if your device wanted to have separate connection to two memory objects.
+
+### PioDevice
+
+This is the base class which all devices senstive to an address range inherit from.
+There are three pure virtual functions which all devices must implement `addressRanges()`, `read()`, and `write()`.
+The magic to choose which mode we are in, etc is handled by the PioPort so the device doesn't have to bother.
+
+Parameters for each device should be in a Params struct derived from `PioDevice::Params`.
+
+### BasicPioDevice
+
+Since most PioDevices only respond to one address range `BasicPioDevice` provides an `addressRanges()` and parameters for the normal pio delay and the address to which the device responds to.
+Since the size of the device normally isn't configurable a parameter is not used for this and anything that inherits from this class is expected to write it's size into pioSize in its constructor.
+
+### DmaPort
+
+The DmaPort (in dma_device.hh) is used only for device mastered accesses.
+The `recvTimingResp()` method must be available to responses (nacked or not) to requests it makes.
+The port has two public methods `dmaPending()` which returns if the dma port is busy (e.g. It is still trying to send out all the pieces of the last request).
+All the code to break requests up into suitably sized chunks, collect the potentially multiple responses and respond to the device is accessed through `dmaAction()`.
+A command, start address, size, completion event, and possibly data is handed to the function which will then execute the completion events `process()` method when the request has been completed.
+Internally the code uses `DmaReqState` to manage what blocks it has received and to know when to execute the completion event.
+
+### DmaDevice
+
+This is the base class from which a DMA non-pci device would inherit from, however none of those exist currently within M5. The class does have some methods `dmaWrite()`, `dmaRead()` that select the appropriate command from a DMA read or write operation.
+
+### NIC Devices
+
+The gem5 simulator has two different Network Interface Cards (NICs) devices that can be used to connect together two simulation instances over a simulated ethernet link.
+
+#### Getting a list of packets on the ethernet link
+
+You can get a list of the packet on the ethernet link by creating a Etherdump object, setting it's file parameter, and setting the dump parameter on the EtherLink to it.
+This is easily accomplished with our fs.py example configuration by adding the command line option \-\-etherdump=\<filename\>. The resulting file will be named \<file\> and be in a standard pcap format.
+This file can be read with [wireshark](https://www.wireshark.org/) or anything else that understands the pcap format.
+
+
+### PCI devices
+```
+To do: Explanation of platforms and systems, how they’re related, and what they’re each for
+```
