Add some documentation about the driver architecture & the plans for filesystem drivers

Author: maxdev1

documentation/drivers/driver-architecture.adoc

@@ -0,0 +1,61 @@
+= Driver architecture
+:toc: left
+include::../common/homelink.adoc[]
+
+The system uses a service-based approach to drivers. The following components
+take their part in this:
+
+* *devicemanager* is the central device registry
+** *libdevice* is the interface library for devicemanager
+
+* *pcidriver* is the PCI driver
+** *libpci* is the interface library for pcidriver
+
+* *ps2driver* is a driver for PS/2 mouse & keyboard input
+** *libps2* is the PS/2 implementation
+** *libps2driver* is the interface library for ps2driver
+
+* *ahcidriver* is the SATA/AHCI implementation
+** *libahci* is the interface library for ahcidriver
+
+* *efifbdriver* is the EFI framebuffer video graphics driver
+* *vmsvgadriver* is the VMSVGA video graphics driver
+* *libvideo* is a generic interface library for video drivers
+
+
+An _interface library_ contains functions used to interact with the driver and
+usually also the purpose-related headers.
+
+
+== Basic initialization
+
+The *devicemanager* first interacts with pcidriver to enumerate PCI devices and
+then, based on available devices, starts up further driver processes.
+
+=== Graphics
+
+Depending on the available devices, one of the available video drivers is
+started. All video drivers implement the video driver interface defined in
+*libvideo*.
+
+The video mode can then be initialized by using _videoDriverSetMode_, which
+is usually done by the *windowserver*.
+
+=== Filesystem
+
+For drives and file systems, the implementation is not finalized but the plan is to have:
+
+* *fsdiscovery* a driver that checks for filesystems on block devices
+    that any driver (like ahcidriver) has registered
+* *libblockdevicedriver* a generic interfacing library for all drivers that
+    implement block devices; must be implemented by ahcidriver
+* *fatdriver* a FAT filesystem driver
+
+The idea is that *fsdiscovery* will wait for block devices being registered;
+if a new device apperas, it will use *libblockdevicedriver* to call *ahcidriver*
+to read the first sector of the drive. Then it will identify what filesystem is
+on that drive and run the respective driver.
+
+For the FAT example, it will start *fatdriver* and tell it the device ID of the
+drive. The driver then again uses *libblockdevicedriver* to interact with
+*ahcidriver* to actually read/write data on the drive.

documentation/index.adoc

@@ -35,4 +35,5 @@ component. On the top of each page there's a link back to this home page.
 * *<<libapi#,libapi>>* - Documentation for the kernel API wrapper library
 * *<<libc#,libc>>* - Documentation for the C library implementation
 * *<<ramdisk-format#,Ramdisk>>* - Documentation about the Ramdisk format & generation
+* *<<driver-architecture#,Driver architecture>>* - Describes driver architecture
 * *<<port#,port.sh>>* - Manual for the porting utility