On Mon, Feb 19, 2007 at 06:56:20PM -0800, H. Peter Anvin wrote:
> It's not a precondition for a file descriptor, either. There are plenty
> of ioctl-only device drivers in existence.
>
> Furthermore, a file descriptor doesn't imply a device entry. Consider
> pipe(2), for example.
>
> As far as the kernel is concerned, a file handle is a nice, uniform
> system for providing communication between the kernel and user space.
> It doesn't matter if one can read() or write() on it; it's perfectly
> normal to support only a subset of the normal operations.
The problem is that sometimes you cannot have a filedescriptor at
all. Think about a PPS source connected with a CPU's GPIO pin. You
have no filedes to use and defining one just for a PPS source or for a
class of PPS sources, I think, is a non sense.
RFC simply doesn't consider the fact that you can have a PPS source
__without__ a filedes connected with, and a single filedes is
considered __always__ connected with a single PPS source.
Ciao,
Rodolfo
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