4 ms·

> If everybody could write drivers then where would be the glory in that... Everyone can write drivers. It's one of the few things we can do in monolith-land.

• jacquesm 8y ago
  > I guess I'm probably missing your point. Yes you are, but that's fine. I totally see why the difference between 'can' and 'actually does' is lost. The reason for that is simple: device driver writing on a monolithic kernel is something of a black art, even with all the tools we have at our disposal today. On a microkernel you'd just be writing any other user process, with access to a couple of ports and and maybe a special hook to handle hw interrupts, but other than that you would not be able to tell the difference. Debugging would be almost as easy as debugging any other user process. You could use a whole slew of high level languages to do your device driver writing. If the interpreters on the system would take care of the lower levels of interacting with the kernel to deal with IO and/or interrupts then you could do your device driver writing in interpreted languages. But, you'll have to wait a little longer to be able to do that. Or try to locate a copy of QnX...
  • zozbot123 8y ago
    > On a microkernel you'd just be writing any other user process, with access to a couple of ports and and maybe a special hook to handle hw interrupts This is a fiction. Hint: if a "user process" can wreak havoc on the system simply by misbehaving (in a way that may or may not be malicious), as drivers interacting with low-level hardware can, it's not a user process in practice, and should not be understood as one. The whole point of making that kernel vs. user space distinction in the first place is so that user programs can't wreak havoc on the system. There are plenty of things that can and should be done in userland (and oftentimes they are, see e.g. Plan9), but drivers are not among these unless you can always rely on something like IOMMU to make sure that the hardware cannot be made to misbehave in a way that affects security guarantees.
    • jacquesm 8y ago
      > This is a fiction. No, it has existed roughly since the mid 80's. Source: programmed a whole bunch of stuff including very fast serial hardware drivers on systems like that. The users process can not wreak havoc on the system, no matter how much it would misbehave in that context. Hardware typically has pretty clearly spelled out bounds and limitations, users processes operate with less rather than more privilege than a kernel side thread would and so have much less in terms of ability to wreck the system. As an extra bonus: a microkernel is small enough that formal verification is an option.
  • ci5er 8y ago
    > Or try to locate a copy of QnX You just made me sooo hard.