Messages in this thread | | | Date | Sun, 9 Jul 2006 10:04:05 -0400 | From | "Jon Smirl" <> | Subject | Re: Opinions on removing /proc/tty? |
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On 7/9/06, Albert Cahalan <acahalan@gmail.com> wrote: > Jon Smirl writes: > > On 7/8/06, Mike Galbraith <efault@gmx.de> wrote: > >> On Fri, 2006-07-07 at 22:56 -0400, Jon Smirl wrote: > > >>> Does anyone use the info in /proc/tty? The hard coded device > >>> names aren't compatible with udev's ability to rename things. > >>> > >>> There also doesn't appear to be any useful info in the drivers > >>> portion that isn't already available in sysfs. I can add some code > >>> to make a list of registered line disciplines appear in sysfs. > >>> > >>> Does anyone have a problem with deleting /proc/tty if > >>> ldisc enum support is added to sysfs? > >> > >> ps uses /proc/tty/drivers, so some coordination would be needed. > > > > Greg, I just looked at the source for ps and it has a bunch > > of fixed code for turning major/minor into /dev/name. Isn't > > that something udevinfo should be doing? But looking at the > > help for udevinfo I don't see any way to turn a major/minor > > into /dev/name. The altermative seems to be search /dev > > looking for the right device node. > > By far, the best thing for procps (ps, top, etc.) would > be /proc/*/tty links. Code that, give everybody a year > to upgrade, and then... maybe. > > There is no way I'm going to have the procps run a "udevinfo" > program, and I very much dislike relying on oddball libraries. > Reliability and performance matter; this isn't some GNOME/KDE > thing that can break just because 1 of 200 libraries changed. > > In order, the procps code tries: > > 1. /proc/*/tty symlink (effectively commented out) Doesn't existing the the current kernel.
> 2. /proc/tty/drivers This info can be wrong due to udev renames. For example tty1 vs tty/1 The info in /proc/tty/drivers describes hardware not processes, it belongs in sysfs, not /proc.
> 3. /proc/*/fd/2 symlink Working in the current kernel
> 4. hard-coded guess This will be wrong because of udev renames. For example tty1 vs tty/1
> 5. /proc/*/fd/255 symlink Working in the current kernel
> 6. "?" Always good
> Long ago, procps would search /dev for the mapping. This was > too slow to be done directly when ps ran, so a binary file in > /etc was used to cache the data. Keeping that file updated > was a major problem.
This is what udev does, it maintains the mapping between devices and names. Udevinfo is how you query the database. /etc/udev is where you control how the device numbers are mapped into names.
Now we have a good example of the impact of pushing something (udev) into user space and not shipping the binary as part of the kernel tree. What is the API for converting a device node number to a name?
> > BTW, cruft gets ripped out some time after Debian-obsolete no > longer supports the old kernels. >
-- Jon Smirl jonsmirl@gmail.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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