Re: [PATCH] x86: Remove readq()/writeq() on 32-bit

From: Hitoshi Mitake
Date: Thu May 14 2009 - 03:19:26 EST


On Wed, 13 May 2009 20:49:26 -0400
Jeff Garzik <jeff@xxxxxxxxxx> wrote:

> H. Peter Anvin wrote:
> > Jeff Garzik wrote:
> >> Judging from this thread and past, I think people will continue to
> >> complain and get confused, even with the above.
> >>
> >
> > Do you really think so? Seems unfortunate, since an API rename would be
> > way more invasive. This is the entirety of the header patch
> > (compile-tested using 32-bit allyesconfig).
>
> The header patch does not lessen the confusion, because you cannot look
> at the code and immediately tell what is going on...
>
> Having a single function's behavior change based on #include selection
> is /not/ intuitive at all, particularly for driver writers. That is
> unlike almost every other Linux API, where functions' behavior stays
> constant across platforms, regardless of magic "under the hood."
>
> That sort of trick is reserved for arch maintainers who know what they
> are doing :)
>
> Jeff
>
>
>

I found another way:
Making architecture with atomic readq/writeq provide HAVE_READQ_ATOMIC/HAVE_WRITEQ_ATOMIC
and making architecture with non-atomic readq/writeq provide HAVE_READQ/HAVE_WRITEQ.
(HAVE_READQ_ATOMIC/HAVE_WRITEQ_ATOMIC should double as HAVE_READQ/HAVE_WRITEQ.)

So driver programmers who need atomic readq/writeq can judge existence of API they really need.
If platform doesn't provide atomic readq/writeq, drivers need these can be disabled by Kconfig.
And bugs Roland and David talking about will be banished.
How about this? > Roland and David
I wrote a test patch. Request for comments.

Signed-off-by: Hitoshi Mitake <h.mitake@xxxxxxxxx>

---
arch/x86/Kconfig | 16 ++++++++++++++--
1 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index df9e885..c94fc48 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -19,8 +19,6 @@ config X86_64
config X86
def_bool y
select HAVE_AOUT if X86_32
- select HAVE_READQ
- select HAVE_WRITEQ
select HAVE_UNSTABLE_SCHED_CLOCK
select HAVE_IDE
select HAVE_OPROFILE
@@ -2022,6 +2020,20 @@ config HAVE_ATOMIC_IOMAP
def_bool y
depends on X86_32

+config HAVE_READQ
+ def_bool y
+
+config HAVE_WRITEQ
+ def_bool y
+
+config HAVE_READQ_ATOMIC
+ def_bool y
+ depends on X86_64
+
+config HAVE_WRITEQ_ATOMIC
+ def_bool y
+ depends on X86_64
+
source "net/Kconfig"

source "drivers/Kconfig"
--
1.5.6.5

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