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Date: Thu, 8 Sep 2011 22:45:20 +0800
From: Yong Zhang <yong.zhang0@gmail.com>
To: Clemens Ladisch <clemens@ladisch.de>
Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@elte.hu,
        Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.de>,
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        Lucas De Marchi <lucas.demarchi@profusion.mobi>,
        Julia Lawall <julia@diku.dk>, Ondrej Zary <linux@rainbow-software.org>,
        Dan Carpenter <error27@gmail.com>, Joe Perches <joe@perches.com>,
        alsa-devel@alsa-project.org
Subject: Re: [RFC] [PATCH 02/62] mpu401:snd_mpu401_uart_new(): split
 semantic of irq_flags
Message-ID: <20110908144519.GB3069@zhy>
Reply-To: Yong Zhang <yong.zhang0@gmail.com>
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On Thu, Sep 08, 2011 at 03:58:45PM +0200, Clemens Ladisch wrote:
> 
> The MPU-401 in UART mode is a very simple and stupid MIDI interface,
> which is used on very many sound cards.  Depending on the actual
> hardware implementation, it gets its own interrupt which may be
> exclusive or sharable, or it is integrated into the interrupt handling
> of the main sound card which means that the sound driver has to call the
> mpu401 interrupt handler explicitly.
> 
> Here, "no interrupt" and "already reserved" actually mean the same thing,
> i.e., that the interrupt handling is the responsibility of some other
> driver.

Thanks. If my understanding is correct, in below combination:

	irq		irq_flags
1)      >=0             >0          /* valid */
2)      >=0             =0          /* invalid, irq should be '-1' */
3)      -1              >0          /* valid, irq_flags just mean real irq_falgs,
                                       but actually there is no irq */
4)      -1              =0          /* valid */

my comment will be true, and we could simplify snd_mpu401_uart_new()
like below:

-	if (irq >= 0 && irq_flags) {
+	if (irq >= 0) {

right?


And then we should audit all the callers of snd_mpu401_uart_new()
to check if they provide the cerrect irq number, but IMOH, that
would more difficult than keeping 'want_irq/irq_reserved'.

Thanks,
Yong