← Back to context

Comment by spijdar

5 hours ago

IOKit was actually built from the ground up for OS X! NeXT had a different driver model called DriverKit. I've never coded against either, but my understanding was they're pretty different beasts. (I could be wrong)

That said, indeed, the abstraction layer here is delightful! I know that some NetBSD devs managed to get PPC Darwin running under a Mach/IOKit compatibility layer back in the day, up to running Xquartz on NetBSD! With NetBSD translating IOKit calls. :-)

6 comments

spijdar

Reply
twoodfin  3 hours ago

There’s a great video of a NeXT-era Steve Jobs keynote floating around—I think the one where he announces the x86 port as NeXT was transitioning to a software-only company—where he specifically calls out DriverKit and how great it is.

Steve was not a developer but he made it his business to care about what they cared about.

erichocean  5 hours ago

As I remember it, they were basically the same—but IOKit is C++ (with restrictions) because 3rd party developers didn't want to learn Objective-C.

But that's a hazy, 20 year old memory.

  • spijdar  1 hour ago

    Yes, you're right! I'm just dolt who's never checked what a .kext on OS X actually is.

    I had been under the impression that DriverKit drivers were quite a different beast, but they're really not. Here's the layout of a NS ".config" bundle:

      ./CG6FrameBuffer.config/English.lproj
  ./CG6FrameBuffer.config/English.lproj/Info.rtf
  ./CG6FrameBuffer.config/English.lproj/Localizable.strings
  ./CG6FrameBuffer.config/CG6FrameBuffer_reloc
  ./CG6FrameBuffer.config/Default.table
  ./CG6FrameBuffer.config/Display.modes
  ./CG6FrameBuffer.config/CG6FrameBuffer

    The driver itself is a Mach-O MH_OBJECT image, flagged with MH_NOUNDEFS. (except for the _reloc images, which are MH_PRELOAD. No clue how these two files relate/interact!)

    Now, on OS X:

      ./AirPortAtheros40.kext/Contents
  ./AirPortAtheros40.kext/Contents/_CodeSignature
  ./AirPortAtheros40.kext/Contents/_CodeSignature/CodeResources
  ./AirPortAtheros40.kext/Contents/MacOS
  ./AirPortAtheros40.kext/Contents/MacOS/AirPortAtheros40
  ./AirPortAtheros40.kext/Contents/Info.plist
  ./AirPortAtheros40.kext/Contents/version.plist

    OS X added a dedicated image type (MH_KEXT_BUNDLE) and they cleaned up a bit, standardized on plists instead of the "INI-esque" .table files, but yeah, basically the same.

  • steve1977  4 hours ago

    From here:

    https://news.ycombinator.com/item?id=10006411

    "At some stage in the future we may be able to move IOKit over to a good programming language"

    • xenadu02  2 hours ago

      IOKit was almost done in Java; C++ was the engineering plan to stop that from happening.

      Remember: there was a short window of time where everyone thought Java was the future and Java support was featured heavily in some of the early OS X announcements.

      Also DriverKit's Objective-C model was not the same as userspace. As I recall the compiler resolved all message sends at compile time. It was much less dynamic.