linux-kernel - Re: [PATCH v4 2/5] irqchip: add virtual demultiplexer implementation

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Date:	Tue, 10 Feb 2015 16:00:13 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>, devicetree@...r.kernel.org,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/5] irqchip: add virtual demultiplexer implementation

On Thu, Jan 29, 2015 at 11:33:37AM +0100, Boris Brezillon wrote:
> +#ifdef CONFIG_VIRT_IRQ_DEMUX_CHIP
> +/**
> + * struct irq_chip_virt_demux - Dumb demultiplexer irq chip data structure

s/Dumb/Virtual/ ?

> + * @domain:		irq domain pointer
> + * @available:		Bitfield of valid irqs
> + * @unmasked:		Bitfield containing irqs status
> + * @flags:		irq_virt_demux_flags flags
> + * @src_irq:		irq feeding the virt demux chip
> + *
> + * Note, that irq_chip_generic can have multiple irq_chip_type
> + * implementations which can be associated to a particular irq line of
> + * an irq_chip_generic instance. That allows to share and protect
> + * state in an irq_chip_generic instance when we need to implement
> + * different flow mechanisms (level/edge) for it.

This seems like a copy/paste from struct irq_chip_generic; it seems not
relevant, seeing how irq_chip_virt_demux does not even have an
irq_chip_type pointer list.

Also, with a demuxer like this, we're bound to whatever flow type its
host is, no?

> +# Dumb interrupt demuxer chip implementation

s/Dumb/Virtual/ ?

> +#ifdef CONFIG_VIRT_IRQ_DEMUX_CHIP
> +/**
> + *	handle_virt_demux_irq - Dumb demuxer irq handle function.

idem

> + *	@irq:	the interrupt number
> + *	@desc:	the interrupt description structure for this irq
> + *
> + *	Dumb demux interrupts are sent from a demultiplexing interrupt handler

idem

> + *	which is not able to decide which child interrupt handler should be
> + *	called.
> + *
> + *	Note: The caller is expected to handle the ack, clear, mask and
> + *	unmask issues if necessary.
> + */

If we're calling multiple handlers, how can they all do this and not
collide?

Over all it looks good -- in as far as my (admittedly stale IRQ
braincells) go.

I'll go queue up these bits, if you could send me a delta patch
addressing these 'minor' comment issues?
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