5 ms·

Idk what you're on about, I mmaped a `/dev/uio` from Python this morning. Yeah, I had to add it in a .dts file and rebuild my image, but even slow as shit high

Idk what you're on about, I mmaped a `/dev/uio` from Python this morning. Yeah, I had to add it in a .dts file and rebuild my image, but even slow as shit high level languages like Python let you bang on registers if you really want to.

notacoward 3y ago
That worked because you were on an OS that supported it, using a device with simple enough behavior that things like timing or extra/elided writes didn't matter. It's great when that works, but there are very many environments and devices for which that option won't exist.
- packetlost 3y ago
  > That worked because you were on an OS that supported it I mean... yeah? I'd be surprised if most operating systems didn't have a facility for directly accessing memory mapped devices in some capacity. Even Windows does I think. Have any examples of an OS that doesn't support banging directly on memory? > using a device with simple enough behavior that things like timing or extra/elided writes didn't matter Yeah, but that's less of a function of the language like GP was referring to and more a property of using a non-RTOS that doesn't play nice with timing sensitive things from user-space. The language itself is not really the issue there, which was my point.
  - deleted 3y ago
    [deleted]
memefrog 3y ago
>I mmaped a `/dev/uio` from Python this morning. You might want to go and have a look at the implementation of 'mmap' in CPython. Here's a clue: it's in the name 'CPython'.
- kaba0 3y ago
  As it is for an OS written in C, sure it does have some helper C wrappers. It is still “syscall”s at the end of the day, and many programming languages can output assembly just fine.
- packetlost 3y ago
  There's nothing special about C that makes it possible to use mmap. Just because CPython happens to be implemented in C doesn't mean anything in this context. I could do the same thing in Go or Hare, neither of which have any C in them and be able to do the same thing.

notacoward 3y ago

That worked because you were on an OS that supported it, using a device with simple enough behavior that things like timing or extra/elided writes didn't matter. It's great when that works, but there are very many environments and devices for which that option won't exist.

packetlost 3y ago
> That worked because you were on an OS that supported it I mean... yeah? I'd be surprised if most operating systems didn't have a facility for directly accessing memory mapped devices in some capacity. Even Windows does I think. Have any examples of an OS that doesn't support banging directly on memory? > using a device with simple enough behavior that things like timing or extra/elided writes didn't matter Yeah, but that's less of a function of the language like GP was referring to and more a property of using a non-RTOS that doesn't play nice with timing sensitive things from user-space. The language itself is not really the issue there, which was my point.
- deleted 3y ago
  [deleted]

memefrog 3y ago

>I mmaped a `/dev/uio` from Python this morning. You might want to go and have a look at the implementation of 'mmap' in CPython. Here's a clue: it's in the name 'CPython'.

kaba0 3y ago
As it is for an OS written in C, sure it does have some helper C wrappers. It is still “syscall”s at the end of the day, and many programming languages can output assembly just fine.
packetlost 3y ago
There's nothing special about C that makes it possible to use mmap. Just because CPython happens to be implemented in C doesn't mean anything in this context. I could do the same thing in Go or Hare, neither of which have any C in them and be able to do the same thing.