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IRC, freenode, #hurd, 2011-10-31:

    <pinotree> is there some example of translator replying to custom ioctl's?
    <pinotree> let's say you define some ioctl (those which can be represented)
      using the _IOW etc macros; how would a translator (or something else)
      "register" and reply to them?
    <youpi> it's not an easy thing
    <youpi> see hurd/hurd/tioctl.defs for instance
    <youpi> that's where the 't' ioctls end up
    <youpi> ('t' being the group in the _IOW macro)
    <braunr> it's not that hard either
    <pinotree> youpi: so you "roll" the ioctl to an ipc call with proper
      parameters?
    <braunr> yes
    <pinotree> ah ok, i thought there was some way to hook new ioctl's, and
      have libc send the whole stuff at once
    <braunr> and the proper number (with a clear name)
    <braunr> hm
    <braunr> for many ioctls, you don't have to change libc
    <youpi> yes, there's a script which produces the .defs from _IOW calls,
      iirc
    <youpi> or something like this
    <youpi> there's also a hook thing in glibc, but for "sane" ioctls, that's
      not needed
    <youpi> (_hurd_lookup_ioctl_handler called by ioctl())
    <youpi> yes, see the rules in hurd/hurd/Makefile
    <youpi> "The following rules assist in creating an `Xioctl.defs' file  to
      define RPCs that are sent primarily by ioctl commands."
    <antrik> well, you can have perfectly sane ioctl()s that still can't be
      expressed within the constraints of the IO* macros... but admittedly
      that's rather uncommon
    <antrik> (unless you consider passing of structs generally insane...)
    <youpi> I didn't want to spend time on finding an appropriate adjective
      instaed of "sane"
    <youpi> while I knew he would understand what I meant (and you did)
    <youpi> (though  maybe not actually)
    <youpi> by "sane", I mean, which use _IOW properly
    <youpi> i.e. with a group, proper numbers, etc.
    <youpi> (the imposed contraints on the parameters is obviously a flaw in
      the hurdish ioctl design, and not insanity from structures)