From: Jamie Lokier <jamie@shareable.org>
To: Duncan Sands <baldrick@free.fr>
Cc: "Helge Hafting" <helgehaf@aitel.hist.no>,
"Måns Rullgård" <mru@kth.se>,
linux-kernel@vger.kernel.org
Subject: Re: udev sysfs docs Re: State of devfs in 2.6?
Date: Fri, 12 Dec 2003 14:51:24 +0000 [thread overview]
Message-ID: <20031212145124.GA13865@mail.shareable.org> (raw)
In-Reply-To: <200312121433.14603.baldrick@free.fr>
Duncan Sands wrote:
> > 2. Keep track of when devices are used, and when they are not busy.
> > We already have this, it's the module reference count.
>
> USB modules (eg: xxxx-hcd) are typically set up so they can be
> unloaded at any time: the act of unloading disconnects any devices
> driven by the module and frees resources. I guess this is
> problematic for your point 2. I understand that some network
> modules work this way too.
I don't see a problem. A HCD device such as a keyboard is always
"active" because it must always be listening for keys as long as the
keyboard is plugged in. You can explicitly "soft unplug" by unloading
the module; the proposal doesn't change that. (Although it would be a
nice interface to copy the PCMCIA method, where you tell the USB
subsystem to disconnect a device instead of having to know which
module(s) to unload).
I agree that in that case, the device is active regardless of its
module reference count. They aren't the same thing.
(Taking it further, USB keyboard is an example of a driver that could
be made permanently demand-pageable as all of the code _could_ be
executed in a process context, if USB's callbacks were made to work
that way, but that road is potentially quite a complicated and error
prone one).
A network device is similar as long as its interface is up (if it's a
device). A protocol module is active as long as it has any active
users, for which various definitions are possible.
Protocol (+ mid-layer, helper modules etc.) show that ideally the
"active" property of a module includes any references to it by other
active modules, which can be interpreted in a simple or a complicated
way, depending on how thoroughly you want modules to be paged out
while still presenting their interfaces in /sys, /dev, /proc,
ifconfig, iptables etc.
-- Jamie
next prev parent reply other threads:[~2003-12-12 14:56 UTC|newest]
Thread overview: 101+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-12-08 15:36 State of devfs in 2.6? Andrew Walrond
2003-12-08 15:42 ` William Lee Irwin III
2003-12-08 15:59 ` Andrew Walrond
2003-12-08 23:38 ` Greg KH
2003-12-09 10:37 ` Andrew Walrond
2003-12-09 10:57 ` Måns Rullgård
2003-12-09 12:54 ` Paul P Komkoff Jr
2003-12-09 5:04 ` Rob Landley
2003-12-08 19:09 ` udev sysfs docs " Bob
2003-12-08 23:37 ` Greg KH
2003-12-09 5:17 ` Witukind
2003-12-09 7:21 ` Bob
2003-12-09 7:39 ` Matthew Reppert
2003-12-09 8:52 ` Måns Rullgård
2003-12-09 9:16 ` Greg KH
2003-12-09 9:45 ` Måns Rullgård
2003-12-09 9:18 ` Greg KH
2003-12-09 9:46 ` Andreas Jellinghaus
2003-12-09 10:25 ` Måns Rullgård
2003-12-09 15:28 ` Andreas Jellinghaus
2003-12-09 20:16 ` Oliver Hunt
2003-12-09 20:53 ` Måns Rullgård
2003-12-09 22:14 ` Olaf Hering
2003-12-09 22:46 ` Oliver Hunt
2003-12-09 23:03 ` Måns Rullgård
2003-12-09 7:56 ` Greg KH
2003-12-09 9:00 ` Xavier Bestel
2003-12-09 9:08 ` Greg KH
2003-12-09 9:19 ` Miles Bader
2003-12-09 9:39 ` Måns Rullgård
2003-12-09 11:01 ` Helge Hafting
2003-12-12 11:26 ` Jamie Lokier
2003-12-12 13:33 ` Duncan Sands
2003-12-12 14:51 ` Jamie Lokier [this message]
2003-12-12 16:34 ` Chuck Campbell
2003-12-12 17:13 ` Chris Friesen
2003-12-12 17:17 ` Måns Rullgård
2003-12-15 2:12 ` Miles Bader
2003-12-15 3:51 ` Mark Mielke
2003-12-15 6:09 ` Tim Connors
2003-12-10 19:23 ` Witukind
2003-12-10 19:33 ` Måns Rullgård
2003-12-10 20:22 ` Witukind
2003-12-10 20:47 ` Ed Sweetman
2003-12-10 20:53 ` Ed Sweetman
2003-12-10 21:31 ` Witukind
2003-12-10 21:28 ` Witukind
2003-12-10 21:48 ` Måns Rullgård
2003-12-11 6:31 ` Witukind
2003-12-10 21:49 ` Måns Rullgård
2003-12-10 23:48 ` Maciej Zenczykowski
2003-12-11 1:53 ` Mark Mielke
2003-12-11 8:42 ` Måns Rullgård
2003-12-11 16:33 ` Mark Mielke
2003-12-10 20:48 ` Måns Rullgård
2003-12-10 23:40 ` Maciej Zenczykowski
2003-12-09 9:55 ` Xavier Bestel
2003-12-09 13:03 ` Maciej Zenczykowski
2003-12-09 15:01 ` Helge Hafting
2003-12-09 18:30 ` Greg KH
2003-12-09 18:53 ` Måns Rullgård
2003-12-10 7:02 ` Xavier Bestel
2003-12-10 20:06 ` Witukind
2003-12-11 9:27 ` Xavier Bestel
2003-12-11 10:15 ` Måns Rullgård
2003-12-11 11:05 ` Xavier Bestel
2003-12-10 0:38 ` Greg KH
2003-12-09 9:26 ` Måns Rullgård
2003-12-09 9:41 ` Miles Bader
2003-12-10 8:13 ` Jakob Oestergaard
2003-12-10 8:24 ` Rob Landley
2003-12-08 23:04 ` Andreas Jellinghaus
2003-12-08 23:34 ` Greg KH
2003-12-09 0:31 ` Sven-Haegar Koch
2003-12-09 0:42 ` Greg KH
2003-12-09 0:51 ` [PATCH] sysfs support for vcs devices (was Re: State of devfs in 2.6?) Greg KH
2003-12-09 5:26 ` State of devfs in 2.6? Rob Landley
2003-12-09 18:19 ` Greg KH
2003-12-09 18:20 ` Greg KH
2003-12-09 7:02 ` Andreas Jellinghaus
2003-12-09 7:13 ` Murray J. Root
2003-12-09 8:21 ` Holger Schurig
2003-12-09 8:52 ` Miles Bader
2003-12-09 10:08 ` Holger Schurig
2003-12-09 17:10 ` Mark Mielke
2003-12-10 5:42 ` Greg KH
2003-12-10 23:29 ` jw schultz
2003-12-11 20:32 ` [2.4.23] cursor dissapears in framebuffer console after switching back from X Witukind
2003-12-11 23:59 ` Gene Heskett
2003-12-12 6:24 ` Witukind
2003-12-09 8:32 ` State of devfs in 2.6? Greg KH
2003-12-09 9:59 ` Jan Dittmer
2003-12-09 13:54 ` Matthew Reppert
2003-12-09 16:27 ` Greg KH
2003-12-09 16:47 ` Eduard Bloch
2003-12-09 19:33 ` Greg KH
2003-12-10 2:15 ` Clemens Schwaighofer
2003-12-10 4:10 ` Bob
2003-12-09 7:33 ` Vojtech Pavlik
2003-12-09 9:48 ` Andreas Jellinghaus
2003-12-08 23:35 ` Greg KH
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