Re: [patch] inotify for 2.6.11

[Arnd Bergmann <arnd@arndb.de>]

On Maandag 07 März 2005 04:13, Albert Cahalan wrote:
> Christoph Hellwig writes:
> > See the review I sent.  Write is exactly the right interface for that kind
> > of thing.  For comment vs argument either put the number first so we don't
> > have the problem of finding a delinator that isn't a valid filename, or
> > use '\0' as such.
> 
> That's just putrid. You've proposed an interface that
> combines the worst of ASCII with the worst of binary.

I guess it's possible to avoid the need for passing the command at all.
The read data already has a format that mixes binary and variable-length
ascii data, so write could use a data structure similar (or even identical)
to the one used there, e.g.

struct inotify_watch_request {
 __u32  mask;  /* watch mask */
 __u32  len;  /* length (including nulls) of name */
 char  name[0]; /* stub for name */
};

This can replace both INOTIFY_WATCH and INOTIFY_IGNORE, if you simply
define a zero mask as a special value for ignore. FIONREAD is a
well-established interface, so I don't think it's necessary to replace
this.

> Adding plain old syscalls is rather nice actually.
> It's only a pain at first, while waiting for glibc
> to catch up.

Yes, that might be a workable interface as well, but don't mix syscalls
with a misc device then. Instead, you might build on something like
futexfs, with syscalls replacing both ioctl and read:

int inotify_open(int flags);
int inotify_watch(int fd, unsigned mask, char *name);
int inotify_ignore(int fd, int wd);
int inotify_getevents(int fd, int max_events, struct inotify_event *);

 Arnd <><