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  1. 02 4月, 2006 4 次提交
  3. 01 4月, 2006 4 次提交
    • D
      [PATCH] Document Linux's memory barriers [try #7] · 108b42b4
      由 David Howells 提交于 
      The attached patch documents the Linux kernel's memory barriers.

I've updated it from the comments I've been given.

The per-arch notes sections are gone because it's clear that there are so many
exceptions, that it's not worth having them.

I've added a list of references to other documents.

I've tried to get rid of the concept of memory accesses appearing on the bus;
what matters is apparent behaviour with respect to other observers in the
system.

Interrupts barrier effects are now considered to be non-existent. They may be
there, but you may not rely on them.

I've added a couple of definition sections at the top of the document: one to
specify the minimum execution model that may be assumed, the other to specify
what this document refers to by the term "memory".

I've made greater mention of the use of mmiowb().

I've adjusted the way in which caches are described, and described the fun
that can be had with cache coherence maintenance being unordered and data
dependency not being necessarily implicit.

I've described (smp_)read_barrier_depends().

I've rearranged the order of the sections, so that memory barriers are
discussed in abstract first, and then described the memory barrier facilities
available on Linux, before going on to more real-world discussions and examples.

I've added information about the lack of memory barriering effects with atomic
ops and bitops.

I've added information about control dependencies.

I've added more diagrams to illustrate caching interactions between CPUs.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      108b42b4
    • A
      [PATCH] fs/namei.c: make lookup_hash() static · a244e169
      由 Adrian Bunk 提交于 
      As announced, lookup_hash() can now become static.
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      a244e169
    • R
      [PATCH] LED: class documentation · 75c1d31d
      由 Richard Purdie 提交于 
      The LED class/subsystem takes John Lenz's work and extends and alters it to
give what I think should be a fairly universal LED implementation.

The series consists of several logical units:

* LED Core + Class implementation
* LED Trigger Core implementation
* LED timer trigger (example of a complex trigger)
* LED device drivers for corgi, spitz and tosa Zaurus models
* LED device driver for locomo LEDs
* LED device driver for ARM ixp4xx LEDs
* Zaurus charging LED trigger
* IDE disk activity LED trigger
* NAND MTD activity LED trigger

Why?
====

LEDs are really simple devices usually amounting to a GPIO that can be turned
on and off so why do we need all this code?  On handheld or embedded devices
they're an important part of an often limited user interface.  Both users and
developers want to be able to control and configure what the LED does and the
number of different things they'd potentially want the LED to show is large.

A subsystem is needed to try and provide all this different functionality in
an architecture independent, simple but complete, generic and scalable manner.

The alternative is for everyone to implement just what they need hidden away
in different corners of the kernel source tree and to provide an inconsistent
interface to userspace.

Other Implementations
=====================

I'm aware of the existing arm led implementation.  Currently the new subsystem
and the arm code can coexist quite happily.  Its up to the arm community to
decide whether this new interface is acceptable to them.  As far as I can see,
the new interface can do everything the existing arm implementation can with
the advantage that the new code is architecture independent and much more
generic, configurable and scalable.

I'm prepared to make the conversion to the LED subsystem (or assist with it)
if appropriate.

Implementation Details
======================

I've stripped a lot of code out of John's original LED class.  Colours were
removed as LED colour is now part of the device name.  Multiple colours are to
be handled as multiple led devices.  This means you get full control over each
colour.  I also removed the LED hardware timer code as the generic timer isn't
going to add much overhead and is just as useful.  I also decided to have the
LED core track the current LED status (to ease suspend/resume handling)
removing the need for brightness_get implementations in the LED drivers.

An underlying design philosophy is simplicity.  The aim is to keep a small
amount of code giving as much functionality as possible.

The major new idea is the led "trigger".  A trigger is a source of led events.
 Triggers can either be simple or complex.  A simple trigger isn't
configurable and is designed to slot into existing subsystems with minimal
additional code.  Examples are the ide-disk, nand-disk and zaurus-charging
triggers.  With leds disabled, the code optimises away.  Examples are
nand-disk and ide-disk.

Complex triggers whilst available to all LEDs have LED specific parameters and
work on a per LED basis.  The timer trigger is an example.

You can change triggers in a similar manner to the way an IO scheduler is
chosen (via /sys/class/leds/somedevice/trigger).

So far there are only a handful of examples but it should easy to add further
LED triggers without too much interference into other subsystems.

Known Issues
============

The LED Trigger core cannot be a module as the simple trigger functions would
cause nightmare dependency issues.  I see this as a minor issue compared to
the benefits the simple trigger functionality brings.  The rest of the LED
subsystem can be modular.

Some leds can be programmed to flash in hardware.  As this isn't a generic LED
device property, I think this should be exported as a device specific sysfs
attribute rather than part of the class if this functionality is required (eg.
 to keep the led flashing whilst the device is suspended).

Future Development
==================

At the moment, a trigger can't be created specifically for a single LED.
There are a number of cases where a trigger might only be mappable to a
particular LED.  The addition of triggers provided by the LED driver should
cover this option and be possible to add without breaking the current
interface.

A CPU activity trigger similar to that found in the arm led implementation
should be trivial to add.

This patch:

Add some brief documentation of the design decisions behind the LED class and
how it appears to users.
Signed-off-by: NRichard Purdie <rpurdie@rpsys.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      75c1d31d
    • N
      [PATCH] mm: schedule find_trylock_page() removal · 93fac704
      由 Nick Piggin 提交于 
      find_trylock_page() is an odd interface in that it doesn't take a reference
like the others.  Now that XFS no longer uses it, and its last remaining
caller actually wants an elevated refcount, opencode that callsite and
schedule find_trylock_page() for removal.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Acked-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      93fac704
  5. 31 3月, 2006 2 次提交
  7. 30 3月, 2006 1 次提交
    • A
      [PATCH] libata: Simplex and other mode filtering logic · 5444a6f4
      由 Alan Cox 提交于 
      Add a field to the host_set called 'flags' (was host_set_flags changed
to suit Jeff)
Add a simplex_claimed field so we can remember who owns the DMA channel
Add a ->mode_filter() hook to allow drivers to filter modes
Add docs for mode_filter and set_mode
Filter according to simplex state
Filter cable in core

This provides the needed framework to support all the mode rules found
in the PATA world. The simplex filter deals with 'to spec' simplex DMA
systems found in older chips. The cable filter avoids duplicating the
same rules in each chip driver with PATA. Finally the mode filter is
neccessary because drive/chip combinations have errata that forbid
certain modes with some drives or types of ATA object.

Drive speed setup remains per channel for now and the filters now use
the framework Tejun put into place which cleans them up a lot from the
older libata-pata patches.
Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>
      5444a6f4
  9. 29 3月, 2006 7 次提交
  11. 28 3月, 2006 7 次提交
  13. 27 3月, 2006 7 次提交
  15. 26 3月, 2006 8 次提交