linux-kernel - Re: [PATCH 2/6] powerpc: make irq_{alloc, free}

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Date:	Wed, 4 May 2011 09:59:05 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Michal Simek <monstr@...str.eu>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-kernel@...r.kernel.org, Ralf Baechle <ralf@...ux-mips.org>,
	hpa@...or.com, Dirk Brandewie <dirk.brandewie@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	devicetree-discuss@...ts.ozlabs.org, x86@...nel.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 2/6] powerpc: make irq_{alloc, free}_virt private and
 remove count argument

On Tue, May 03, 2011 at 11:47:47AM +1000, Benjamin Herrenschmidt wrote:
> On Thu, 2011-04-28 at 14:01 -0600, Grant Likely wrote:
> > irq_alloc_virt() and irq_free_virt() aren't called anywhere but from
> > arch/powerpc/kernel/irq.c, and they are only ever called with count=1.
> > This patch removes the prototypes from the header file, removes the
> > count arguments, and cuts out the dead code.
> > 
> > Also removes obsolete references to irq_early_init()
> 
> Nack.
> 
> The count was intended to be able to allocate blocks of interrupts. This
> was not used so far because we didn't support MSI blocks (for non-X
> MSIs) but that is coming, and unfortunately, the API that was designed
> for that is crap and requires contiguous IRQ numbers on the linux side
> as well as on the device side (well device side is a HW requirement but
> we could have been smarter on the Linux side).
> 
> So the ability to allocate blocks will be needed. In fact it's not clear
> yet whether we'll also need them to be naturally aligned powers of two
> or not at this stage. It depends how the bloody API is going to be used
> by drivers.

Heh, I wondered about that, but there hasn't been any users for at
least 5 years (as evidenced by commit e12514650b, "Fix loop logic in
irq_alloc_virt()") so it was looking pretty dead, and it made the
patch to switch to using irq_alloc_desc*() quite a bit simpler if it
was removed.  :-)

I'm not particularly attached to this patch, so I can drop it from the
series.

g.

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