lkml.org 
[lkml]   [1999]   [Oct]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [linux-usb] Re: USB device allocation
Date
In article <linux.kernel.199910081727.KAA04826@zack.bitmover.com>,
Zack Weinberg <zack@bitmover.com> wrote:

>If the user visible dev_t is changed, the new representation has to
>obey a few simple constraints and all the system calls that pass
>device numbers in and out of the kernel have to get new versions.
>That's stat, fstat, lstat, mknod, and maybe a couple of ioctls.
>
>99% of user space code will not notice AT ALL.
>
>0.9% of user space code gets dev_t values from stat() and compares
>them for equality. It will break mildly until the C library is
>updated to use the new system calls. (Note glibc's dev_t is already
>64 bits wide.) For example, a program has a chance of mistakenly
>thinking that two files on different mounted filesystems - say, one on
>device #3,2 and one on #258,2 - are the same file.

Or thinking that the two filesystems are the same.

As you point out, the gotchas won't happen very often, but they
will happen.

I'd love to see dev_t pushed out to some unreasonable size (even
with d*vfs; plan-9 namespaces are great, but backwards
compatability is better) and the kernel version bumped up to 3.0 --
this would give a wonderful opportunity to widen out some of the
overly constrained entry points (with a update document saying
``EVERYTHING YOU'VE EVER WRITTEN HAS JUST BROKEN. RECOMPILE IT
ALL'', or the FreeBSD linux emulator could be ported to Linux
for pdp-11, er, pre 3.0 code.) as well as discard some of the
old interfaces (like the old fcntl interfaces.)

>David Parsons will have to put a larger dev_t into libc4.

It would give me a good opportunity to do libc7 and take out gnu
db and curses, too.

____
david parsons \bi/ and with 3.0, we could put UDI into the kernel
\/ and start scavenging device drivers from other
operating systems.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:54    [W:0.102 / U:0.148 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site