linux-kernel - Re: [PATCH 6/7] spi/mpc8xxx: don't check platform_get

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Date:	Thu, 17 Dec 2009 14:05:49 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Anton Vorontsov <avorontsov@...mvista.com>
Cc:	linux-kernel@...r.kernel.org, David Vrabel <david.vrabel@....com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	Grant Likely <grant.likely@...retlab.ca>,
	Kumar Gala <galak@...nel.crashing.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	spi-devel-general@...ts.sourceforge.net,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 6/7] spi/mpc8xxx: don't check platform_get_irq's return
	value against zero

Hi Anton,

On Wed, Dec 16, 2009 at 10:37:45PM +0300, Anton Vorontsov wrote:
> On Wed, Dec 16, 2009 at 08:18:39PM +0100, Uwe Kleine-König wrote:
> [...]
> > > > I'm a bit annoyed as this is the third time[1] this month this irq0
> > > > discussion pops up for me.  I think people see that irq0 is involved
> > > > somehow, start wailing and stop seeing the issues being fixed.
> > > 
> > > For this particular driver, there is NO issue whatsoever. It is
> > > only used for PowerPC, which has VIRQ0 == invalid IRQ. And note
> > > that there still could be HWIRQ0 on PowerPC, but it is *never*
> > > mapped to VIRQ0.
> > Yes, there is an issue.  If the platform device doesn't have a resource
> > specifing the irq, platform_get_irq returns -ENXIO.  So in the driver
> > (unsigned)(-ENXIO) is passed to mpc8xxx_spi_probe as (!(-ENXIO)) is
> > false and so the error isn't catched.
> 
> If you look into how we create the platform device, you'll notice
> that -ENXIO isn't possible.
> It's in arch/powerpc/platforms/83xx/mpc832x_rdb.c:of_fsl_spi_probe(),
> which is a legacy interface that I'd like to be removed anyway.
> 
> Though, if you want to fix the inconsistency in the platform device
> API, then I'd suggest to fix the platform_get_irq(). The driver itself
> is correct.
With platform_get_irq as it is today, the check in

	irq = platform_get_irq(pdev, 0);
	if (!irq)
		return -EINVAL;

is non-sense as !irq always evaluates to 0.  If your argue that the
resources are right, then the logical consequence is to strip down
plat_mpc8xxx_spi_probe to just

	struct spi_master *master;
	master = mpc8xxx_spi_probe(&pdev->dev,
		platform_get_resource(pdev, IORESOURCE_MEM, 0)
		platform_get_irq(pdev, 0));
	if (IS_ERR(master))
		return PTR_ERR(master);
	return 0;

Best regards
Uwe

-- 
Pengutronix e.K.                              | Uwe Kleine-König            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |
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