| # Device model |
| |
| Caution: This page may contain information that is specific to the legacy |
| version of the driver framework (DFv1). |
| |
| ## Introduction |
| |
| In Fuchsia, device drivers are implemented as ELF shared libraries (DSOs), which are |
| loaded into Driver Host processes. The Driver Manager process, |
| contains the Device Coordinator which keeps track of drivers and devices, manages |
| the discovery of drivers, the creation and direction of Driver Host processes, and |
| maintains the Device Filesystem (devfs), which is the mechanism through which userspace |
| services and applications (constrained by their namespaces) gain access to devices. |
| |
| The Driver Manager views devices as part of a single unified tree. |
| The branches (and sub-branches) of that tree consist of some number of |
| devices within a Driver Host process. The decision as to how to sub-divide |
| the overall tree among Driver Hosts is based on system policy for isolating |
| drivers for security or stability reasons and colocating drivers for performance |
| reasons. |
| |
| |
| ## Devices, Drivers, and Driver Hosts |
| |
| Here's a (slightly trimmed for clarity) dump of the tree of devices in |
| Fuchsia running on Qemu x86-64: |
| |
| ```sh |
| $ driver dump |
| [root] |
| <root> pid=1509 |
| [null] pid=1509 /boot/driver/builtin.so |
| [zero] pid=1509 /boot/driver/builtin.so |
| [misc] |
| <misc> pid=1645 |
| [console] pid=1645 /boot/driver/console.so |
| [dmctl] pid=1645 /boot/driver/dmctl.so |
| [ptmx] pid=1645 /boot/driver/pty.so |
| [i8042-keyboard] pid=1645 /boot/driver/pc-ps2.so |
| [hid-device-001] pid=1645 /boot/driver/hid.so |
| [i8042-mouse] pid=1645 /boot/driver/pc-ps2.so |
| [hid-device-002] pid=1645 /boot/driver/hid.so |
| [sys] |
| <sys> pid=1416 /boot/driver/bus-acpi.so |
| [acpi] pid=1416 /boot/driver/bus-acpi.so |
| [pci] pid=1416 /boot/driver/bus-acpi.so |
| [00:00:00] pid=1416 /boot/driver/bus-pci.so |
| [00:01:00] pid=1416 /boot/driver/bus-pci.so |
| <00:01:00> pid=2015 /boot/driver/bus-pci.proxy.so |
| [bochs_vbe] pid=2015 /boot/driver/bochs-vbe.so |
| [framebuffer] pid=2015 /boot/driver/framebuffer.so |
| [00:02:00] pid=1416 /boot/driver/bus-pci.so |
| <00:02:00> pid=2052 /boot/driver/bus-pci.proxy.so |
| [e1000] pid=4628 /boot/driver/e1000.so |
| [ethernet] pid=2052 /boot/driver/ethernet.so |
| [00:1f:00] pid=1416 /boot/driver/bus-pci.so |
| [00:1f:02] pid=1416 /boot/driver/bus-pci.so |
| <00:1f:02> pid=2156 /boot/driver/bus-pci.proxy.so |
| [ahci] pid=2156 /boot/driver/ahci.so |
| [00:1f:03] pid=1416 /boot/driver/bus-pci.so |
| ``` |
| |
| The names in square brackets are devices. The names in angle brackets are |
| proxy devices, which are instantiated in the "lower" driver host, when process |
| isolation is being provided. The pid= field indicates the process object |
| id of the driver host process that device is contained within. The path indicates |
| which driver implements that device. |
| |
| Above, for example, the pid 1416 driver host contains the pci bus driver, which has |
| created devices for each PCI device in the system. PCI device 00:02:00 happens |
| to be an intel ethernet interface, which we have a driver for (e1000.so). |
| A new driver host (pid 2052) is created, set up with a proxy device for PCI 00:02:00, |
| and the intel ethernet driver is loaded and bound to it. |
| |
| Proxy devices are invisible within the Device filesystem, so this ethernet device |
| appears as `/dev/sys/platform/pci/00:02:00/e1000`. |
| |
| ### Driver Framework Version 2 (DFv2) |
| In driver framework version 2, devices are referred to as nodes and the dump of |
| the tree of nodes will look slightly different: |
| |
| ```sh |
| $ driver dump |
| [root] pid=4766 fuchsia-boot:///#meta/platform-bus.cm |
| [sys] pid=4766 |
| [platform] pid=4766 |
| [pt] pid=4766 fuchsia-boot:///#meta/platform-bus-x86.cm |
| [acpi] pid=4766 |
| [pwrbtn] pid=4766 fuchsia-boot:///#meta/hid.cm |
| [_SB_] pid=4766 |
| [PCI0] pid=4766 |
| [ISA_] pid=4766 |
| [RTC_] pid=7264 fuchsia-boot:///#meta/intel-rtc.cm |
| [rtc] pid=7264 |
| [KBD_] pid=7359 fuchsia-boot:///#meta/pc-ps2.cm |
| [i8042] pid=7359 |
| [i8042-keyboard] pid=7359 |
| [i8042-mouse] pid=7359 |
| [MOU_] pid=4766 |
| [COM1] pid=4766 |
| [PRES] pid=4766 |
| [GPE0] pid=4766 |
| [FWCF] pid=4766 |
| [S00_] pid=4766 |
| [S08_] pid=4766 |
| [S10_] pid=4766 |
| [S18_] pid=4766 |
| [S20_] pid=4766 |
| [S28_] pid=4766 |
| [S30_] pid=4766 |
| [S38_] pid=4766 |
| [S58_] pid=4766 |
| [HPET] pid=4766 |
| [LNKE] pid=4766 |
| [LNKF] pid=4766 |
| [LNKG] pid=4766 |
| [LNKH] pid=4766 |
| [GSIE] pid=4766 |
| [GSIF] pid=4766 |
| [GSIG] pid=4766 |
| [GSIH] pid=4766 |
| [GFBY] pid=4766 |
| [GFEV] pid=4766 |
| [GFPP] pid=4766 |
| [GFFB] pid=4766 |
| [GFAU] pid=4766 |
| [GFSK] pid=4766 |
| [GFRT] pid=4766 |
| [GFRO] pid=4766 |
| [CPUS] pid=4766 |
| [_TZ_] pid=4766 |
| [PCI0] pid=4766 fuchsia-boot:///#meta/bus-pci.cm |
| [bus] pid=4766 |
| [00_00_0] pid=4766 |
| [00_00_0_] pid=4766 |
| [00_01_0] pid=4766 |
| [00_01_0_] pid=4766 |
| [00_02_0] pid=4766 fuchsia-boot:///#meta/virtio_block.cm |
| [virtio-block] pid=4766 fuchsia-boot:///#meta/block.core.cm |
| [block] pid=4766 fuchsia-boot:///#meta/fvm.cm |
| [fvm] pid=4766 |
| [blobfs-p-1] pid=4766 fuchsia-boot:///#meta/block.core.cm |
| [block] pid=4766 |
| [data-p-2] pid=4766 fuchsia-boot:///#meta/block.core.cm |
| [block] pid=4766 fuchsia-boot:///#meta/zxcrypt.cm |
| [zxcrypt] pid=4766 |
| [unsealed] pid=4766 fuchsia-boot:///#meta/block.core.cm |
| [block] pid=4766 |
| [00_02_0_] pid=4766 |
| [00_03_0] pid=4766 |
| [00_03_0_] pid=4766 |
| [00_04_0] pid=4766 fuchsia-boot:///#meta/virtio_ethernet.cm |
| [virtio-net] pid=4766 fuchsia-boot:///#meta/netdevice-migration.cm |
| [netdevice-migration] pid=4766 fuchsia-boot:///#meta/network-device.cm |
| [network-device] pid=4766 |
| [00_04_0_] pid=4766 |
| [00_05_0] pid=4766 |
| [00_05_0_] pid=4766 |
| [00_06_0] pid=4766 |
| [00_06_0_] pid=4766 |
| [00_07_0] pid=4766 |
| [00_07_0_] pid=4766 |
| [00_0b_0] pid=4766 |
| [00_0b_0_] pid=4766 |
| [00_1f_0] pid=4766 |
| [00_1f_0_] pid=4766 |
| [00_1f_2] pid=4766 |
| [00_1f_2_] pid=4766 |
| [00_1f_3] pid=4766 |
| [00_1f_3_] pid=4766 |
| [ram-disk] pid=4766 fuchsia-boot:///#meta/ramdisk.cm |
| [ramctl] pid=4766 |
| [ram-nand] pid=4766 |
| [virtual-audio] pid=4766 fuchsia-pkg://fuchsia.com/virtual_audio#meta/virtual_audio_driver.cm |
| [virtual_audio] pid=4766 |
| [bt-hci-emulator] pid=4766 |
| [00_00_1b] pid=4766 fuchsia-boot:///#meta/sysmem.cm |
| [sysmem] pid=4766 |
| ``` |
| |
| The names in square brackets are nodes. The pid= field indicates the process |
| object id of the driver host process that device is contained within. The URL is |
| the component manifest of the driver that is bound to the node. Nodes that do |
| not have a URL do not have a driver bound to them. |
