linux-kernel - Re: [RFC] [PATCH 02/62] mpu401:snd_mpu401_uart_new(): split semantic of irq

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Message-ID: <4E69253F.3090705@ladisch.de>
Date:	Thu, 08 Sep 2011 22:27:43 +0200
From:	Clemens Ladisch <clemens@...isch.de>
To:	Yong Zhang <yong.zhang0@...il.com>
CC:	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...e.hu,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>, Jiri Kosina <jkosina@...e.cz>,
	Andreas Mohr <andi@...as.de>,
	Lucas De Marchi <lucas.demarchi@...fusion.mobi>,
	Julia Lawall <julia@...u.dk>,
	Ondrej Zary <linux@...nbow-software.org>,
	Dan Carpenter <error27@...il.com>,
	Joe Perches <joe@...ches.com>, alsa-devel@...a-project.org
Subject: Re: [RFC] [PATCH 02/62] mpu401:snd_mpu401_uart_new(): split semantic
 of irq_flags

Yong Zhang wrote:
> On Thu, Sep 08, 2011 at 03:58:45PM +0200, Clemens Ladisch wrote:
> > ...
> > Here, "no interrupt" and "already reserved" actually mean the same thing,
> > i.e., that the interrupt handling is the responsibility of some other
> > driver.

Sorry, after checking the code, I've realized that my description was
wrong.  irq_flags==0 ("already reserved") means that snd_mpu401_uart_new
should not try to allocate the interrupt, while irq==-1 ("no interrupt")
means that the device never issues mpu401 interrupts, so that the mpu401
code must use a timer to poll the device.

I'll write a patch that changes this function so that irq<0 means
"already reserved", and that "no interrupt" gets another bit in the
info_flags parameter.


Regards,
Clemens
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