linux-kernel - Re: [PATCH v3 3/4] PCI/MSI: Add helper function pci_msi_domain_get_msi

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Date:	Thu, 01 Oct 2015 10:24:44 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	David Daney <ddaney.cavm@...il.com>, linux-kernel@...r.kernel.org,
	Will Deacon <will.deacon@....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>,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	Grant Likely <grant.likely@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Frank Rowand <frowand.list@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org
CC:	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH v3 3/4] PCI/MSI:  Add helper function pci_msi_domain_get_msi_rid().

Hi David,

On 30/09/15 23:47, David Daney wrote:
> From: David Daney <david.daney@...ium.com>
> 
> Add pci_msi_domain_get_msi_rid() to return the MSI requester id (RID).
> Initially needed by gic-v3 based systems. It will be used by follow on
> patch to drivers/irqchip/irq-gic-v3-its-pci-msi.c
> 
> Initially supports mapping the RID via OF device tree.  In the future,
> this could be extended to use ACPI _IORT tables as well.
> 
> Signed-off-by: David Daney <david.daney@...ium.com>
> ---
>  drivers/pci/msi.c   | 31 +++++++++++++++++++++++++++++++
>  include/linux/msi.h |  1 +
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index d449714..92b6dc9 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -20,6 +20,7 @@
>  #include <linux/io.h>
>  #include <linux/slab.h>
>  #include <linux/irqdomain.h>
> +#include <linux/of_irq.h>
>  
>  #include "pci.h"
>  
> @@ -1327,4 +1328,34 @@ struct irq_domain *pci_msi_create_default_irq_domain(struct device_node *node,
>  
>  	return domain;
>  }
> +
> +struct get_mis_id_data {
> +	u32	alias;
> +};
> +
> +static int get_msi_id_cb(struct pci_dev *pdev, u16 alias, void *data)
> +{
> +	struct get_mis_id_data *s = data;
> +
> +	s->alias = alias;
> +	return 0;
> +}

Why not use a naked u32, since you only have a single field in this
structure? Or is it that you are anticipating other fields there?

> +/**
> + * pci_msi_domain_get_msi_rid - Get the MSI requester id (RID)
> + * @domain:	The interrupt domain
> + * @pdev:	The PCI device.
> + *
> + * The RID for a device is formed from the alias, with a firmware
> + * supplied mapping applied
> + *
> + * Returns: The RID.
> + */
> +u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev)
> +{
> +	struct get_mis_id_data d;
> +
> +	d.alias = 0;
> +	pci_for_each_dma_alias(pdev, get_msi_id_cb, &d);
> +	return of_msi_map_rid(&pdev->dev, domain->of_node, d.alias);

Should you check whether domain->of_node is NULL first? I don't think
of_msi_map_rid would have any problem with that, but a domain that is
not backed by an of_node makes me feel a bit uneasy and would tend to
indicate that we're not using DT.

> +}
>  #endif /* CONFIG_PCI_MSI_IRQ_DOMAIN */
> diff --git a/include/linux/msi.h b/include/linux/msi.h
> index ad939d0..56e3b76 100644
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -293,6 +293,7 @@ irq_hw_number_t pci_msi_domain_calc_hwirq(struct pci_dev *dev,
>  					  struct msi_desc *desc);
>  int pci_msi_domain_check_cap(struct irq_domain *domain,
>  			     struct msi_domain_info *info, struct device *dev);
> +u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev);
>  #endif /* CONFIG_PCI_MSI_IRQ_DOMAIN */
>  
>  #endif /* LINUX_MSI_H */
> 

Otherwise looks good to me.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...
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