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Sat May 1 20:15:13 2010 UTC (12 years, 2 months ago) by wiki
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web commit by jakllsch: some notes on ddb usage

# Jonathan Kollasch

## [[!template id=man name="ddb" section="4"]] tips

### locating a softc
This locates a device's softc using it's `cfdriver_t` (e.g. `&mainbus_cd`, `&cpu_cd`) and its "device unit" (e.g. the `0` in `mainbus0`).

    db{0}> call device_lookup_private(ohci_cd, 0)

### locating structure members
This uses [[!template id=man name="gdb" section="1"]] and a kernel with debugging symbols to find the offset to a element in a structure.

    $ gdb netbsd.gdb
    (gdb) print &((struct ohci_softc *)0)->iot
    $3 = (bus_space_tag_t *) 0x478
    (gdb) print &((struct ohci_softc *)0)->ioh
    $4 = (bus_space_handle_t *) 0x480

### peeking at mapped registers

    db{0}> call bus_space_read_4(*(ffff800045fb2008+478), *(ffff800045fb2008+480), 0)

## Unfinished Projects

### x86 UEFI kernel loader
Building this for x64 UEFI requires the `ms_abi` function attribute introduced in GCC 4.4 or so.
This project uses Intel UEFI headers and some existing FreeBSD work.
Needs more work and cleanup, also toolchain updates.
Work has been done using the OVMF BIOS images for Qemu.

### bcm47xx for evbmips
Boots multiuser on NFS root, needs more work and cleanup.
This project is on hold until there's a miniature userland that fits in 4-8MiB flash storage devices, on a flash-oriented file system.
[[!template id=man name="bce" section="4"]] and [[!template id=man name="bwi" section="4"]] would need refactoring to be bus-independent.

### Conexant PCI DTV driver
I have some code for 23880-3 and 887 host interfaces.
This type of hardware is hard to find freely available docs for.
Tuner/demod drivers from Linux could be ported, but would still be GPLed.
Probably better to keep these drivers in userland.

Should try to coordinate with what FreeBSD is doing: <>.

### Memory-mapped PCI config access on x86
Needs cleanup, and maybe some more validation of MCFG tables.

### Toshiba ACPI LCD backlight driver
Loosly based on [[!template id=man name="vald" section="4"]]. Currently attaches to `TOS1900`/`VALZ`, but doesn't interact with this device.
This driver should really attach to `\_SB.PCI0.GFX0.LCD` or
`\_SB.PCI0.PEGP.VGA.LCD`, which are the devices that get notified of
brightness button pushes, and contain the `_BCL`, `_BCM`, and `_BQC`
methods that access the brightness adjustment function.
Such an attachment does not appear to be possible (or at the very least, easy)
at present.

## Possible Projects
### AMD PowerNow/Cool'n'Quiet states loaded from ACPI tables

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