linux-kernel - Re: [RFC PATCH 2/6] DRIVERS: IRQCHIP: CROSSBAR: Add support for Crossbar IP

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Date:	Thu, 24 Oct 2013 11:20:12 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Sricharan R <r.sricharan@...com>
cc:	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-omap@...r.kernel.org, linus.walleij@...aro.org,
	santosh.shilimkar@...com, linux@....linux.org.uk, tony@...mide.com,
	rnayak@...com, marc.zyngier@....com, grant.likely@...aro.org,
	rob.herring@...xeda.com, mark.rutland@....com
Subject: Re: [RFC PATCH 2/6] DRIVERS: IRQCHIP: CROSSBAR: Add support for
 Crossbar IP

On Mon, 30 Sep 2013, Sricharan R wrote:
> +/*
> + * @int_max: maximum number of supported interrupts
> + * @irq_map: array of interrupts to crossbar number mapping
> + * @crossbar_base: crossbar base address
> + * @register_offsets: offsets for each irq number
> + */
> +struct crossbar_device {
> +	uint int_max;
> +	uint *irq_map;

Why do you need another map here?

Isn't the linear_revmap of the irqdomain sufficient?

> +static inline const u32 allocate_free_irq(int cb_no)
> +{
> +	int i;
> +
> +	for (i = 0; i < cb->int_max; i++) {
> +		if (cb->irq_map[i] == IRQ_FREE) {
> +			cb->irq_map[i] = cb_no;
> +			return i;
> +		}
> +	}
> +
> +	return -ENODEV;
> +}
> +
> +static int crossbar_domain_xlate(struct irq_domain *d,
> +				 struct device_node *controller,
> +				 const u32 *intspec, unsigned int intsize,
> +				 unsigned long *out_hwirq,
> +				 unsigned int *out_type)
> +{
> +	return allocate_free_irq(intspec[1]) + GIC_IRQ_START;

Mooo. In the error case you return:

      -ENODEV + GIC_IRQ_START == -19 + 32 == 13

Yikes.

> +
> +	/*
> +	 * Register offsets are not linear because of the
> +	 * reserved irqs. so find and store the offsets once.
> +	 */
> +	for (i = 0; i < max; i++) {
> +		if (!cb->irq_map[i])
> +			continue;
> +
> +		cb->register_offsets[i] = reserved;
> +		reserved += size;

I'm amazed by such a brilliant hardware design.

Thanks,

	tglx
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