Re: LANANA: To Pending Device Number Registrants

[Richard Gooch]

Ingo Oeser writes:
> On Tue, May 15, 2001 at 08:10:29AM -0700, Linus Torvalds wrote:
> > and I don't see why we couldn't expose the "driver
> > name" for any file descriptor.
> 
> Because we dont like to replace:
> 
>    if (st.device == MAJOR_1)
>       bla
>    else if ...
> 
> with
> 
>    if (!strcmp(st.device,"driver_1") )
>       bla
>    else if ...
> 
> ?
> 
> There is no win doing it this way, because every time we add a
> new driver that fits or change the name of one, we need add
> support for it.

Now look at how we can already do these things with devfs. Let's say
I've opened /dev/cdroms/cdrom0 and it's sitting on fd=3.
% ls -lF /proc/self/fd/3
lrwx------   1 root     root           64 May 15 13:24 /proc/self/fd/3 -> 
/dev/ide/host0/bus0/target1/lun0/cd

So, in my application I do:
        len = readlink ("/proc/self/3", buffer, buflen);
        if (strcmp (buffer + len - 2, "cd") != 0) {
                fprintf (stderr, "Not a CD-ROM! Bugger off.\n");
                exit (1);
        }
        if (strncmp (buffer, "/dev/ide", 8) == 0) do_ide (fd);
        else if (strncmp (buffer, "/dev/scsi", 9) == 0) do_scsi (fd);
        else do_generic (fd);

That's a lot cleaner than relying on magic numbers, IMNSHO.

                                Regards,

                                        Richard....
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