linux-kernel - Re: [PATCH 1/3] irq: Set multiple MSI descriptor data for multiple IRQs

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Date:	Thu, 06 Jun 2013 00:03:08 +0100
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Mike Qiu <qiudayu@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:	benh@...nel.crashing.org, tglx@...utronix.de,
	Mike Qiu <qiudayu@...ux.vnet.ibm.com>
Subject: Re: [PATCH 1/3] irq: Set multiple MSI descriptor data for multiple IRQs

On Tue, 15 Jan 2013 15:38:54 +0800, Mike Qiu <qiudayu@...ux.vnet.ibm.com> wrote:
> Multiple MSI only requires the IRQ in msi_desc entry to be set as
> the value of irq_base.
> 
> This patch implements the above mentioned technique.
> 
> Signed-off-by: Mike Qiu <qiudayu@...ux.vnet.ibm.com>

Hi Mike,

question below...

> ---
> +int irq_set_multiple_msi_desc(unsigned int irq_base, unsigned int nvec,
> +				struct msi_desc *entry)
> +{
> +	unsigned long flags, i;
> +	struct irq_desc *desc;
> +
> +	for (i = 0; i < nvec; i++) {
> +		desc = irq_get_desc_lock(irq_base + i, &flags,
> +					IRQ_GET_DESC_CHECK_GLOBAL);
> +		if (!desc)
> +			return -EINVAL;
> +		desc->irq_data.msi_desc = entry;
> +		if (i == 0 && entry)
> +			entry->irq = irq_base;

It's not clear to me why this code only sets the irq value for the first
desc. Why don't the other descs in the array want (irq_base + i) here? A
comment describing what is going on would be appropriate and helpful.

g.
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