From: Matthew Garrett <mjg59@srcf.ucam.org>
To: Arjan van de Ven <arjan@infradead.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH, RFC] Driver for reading HP laptop LCD brightness
Date: Sun, 5 Feb 2006 14:34:46 +0000 [thread overview]
Message-ID: <20060205143446.GA22494@srcf.ucam.org> (raw)
In-Reply-To: <1139149647.3131.26.camel@laptopd505.fenrus.org>
On Sun, Feb 05, 2006 at 03:27:26PM +0100, Arjan van de Ven wrote:
> disable_irq() and enable_irq() are really really evil. Are you sure you
> need these? To me on first sight it looks like a bug (think of shared
> interrupts for example), can you explain what you are trying to achieve
> with these?
We're talking to the hardware directly. There's a potential race where
the BIOS will try to access the cmos at the same time, with potentially
interesting results (We set the address we want to read with the outb.
The BIOS runs, outbs its own address, and then reads. We then read from
the address the BIOS was looking at, rather than what we were looking
at).
On all the hardware this will run on, IRQ 8 is the RTC. I don't believe
it can share interrupts.
--
Matthew Garrett | mjg59@srcf.ucam.org
next prev parent reply other threads:[~2006-02-05 14:34 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-05 13:55 [PATCH, RFC] Driver for reading HP laptop LCD brightness Matthew Garrett
2006-02-05 14:27 ` Arjan van de Ven
2006-02-05 14:34 ` Matthew Garrett [this message]
2006-02-05 14:41 ` Arjan van de Ven
2006-02-05 14:45 ` Matthew Garrett
2006-02-05 21:49 ` Pavel Machek
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