RE: [PATCH 2/5] gic-its: Allow pci_requester_id to be overridden.

[Pavel Fedin <p.fedin@samsung.com>]

 Hello!

> -----Original Message-----
> From: linux-pci-owner@vger.kernel.org [mailto:linux-pci-owner@vger.kernel.org] On Behalf Of David
> Daney
> Sent: Wednesday, July 15, 2015 7:55 PM
> To: linux-arm-kernel@lists.infradead.org; Catalin Marinas; Will Deacon; Bjorn Helgaas; linux-
> pci@vger.kernel.org; Thomas Gleixner; Jason Cooper
> Cc: linux-kernel@vger.kernel.org; Robert Richter; David Daney
> Subject: [PATCH 2/5] gic-its: Allow pci_requester_id to be overridden.
> 
> From: David Daney <david.daney@cavium.com>
> 
> Signed-off-by: David Daney <david.daney@cavium.com>
> ---
>  drivers/irqchip/irq-gic-v3-its.c   | 14 +++++++++++++-
>  include/linux/irqchip/arm-gic-v3.h |  2 ++
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 1b7e155..4580970 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -1189,11 +1189,23 @@ static int its_pci_msi_vec_count(struct pci_dev *pdev)
>  	return max(msi, msix);
>  }
> 
> +static u32 its_dflt_pci_requester_id(struct pci_dev *pdev, u16 alias)
> +{
> +	return alias;
> +}
> +
> +static its_pci_requester_id_t its_pci_requester_id = its_dflt_pci_requester_id;
> +void set_its_pci_requester_id(its_pci_requester_id_t fn)
> +{
> +	its_pci_requester_id = fn;
> +}
> +EXPORT_SYMBOL(set_its_pci_requester_id);

 IMHO having a globally defined function is a horrible approach. What if some HW has two different
PCI host controllers, each of them wants to provide different form of IDs? I know, this is just
imaginary, but still...
 What if instead of this function we simply add a field to a struct pci_bus ? Then bus driver would
fill in HW-specific ID bits for every bus.
 I can send a patch if interested.

> +
>  static int its_get_pci_alias(struct pci_dev *pdev, u16 alias, void *data)
>  {
>  	struct its_pci_alias *dev_alias = data;
> 
> -	dev_alias->dev_id = alias;
> +	dev_alias->dev_id = its_pci_requester_id(pdev, alias);
>  	if (pdev != dev_alias->pdev)
>  		dev_alias->count += its_pci_msi_vec_count(dev_alias->pdev);
> 
> diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
> index ffbc034..18e3757 100644
> --- a/include/linux/irqchip/arm-gic-v3.h
> +++ b/include/linux/irqchip/arm-gic-v3.h
> @@ -389,6 +389,8 @@ int its_cpu_init(void);
>  int its_init(struct device_node *node, struct rdists *rdists,
>  	     struct irq_domain *domain);
> 
> +typedef u32 (*its_pci_requester_id_t)(struct pci_dev *, u16);
> +void set_its_pci_requester_id(its_pci_requester_id_t fn);
>  #endif
> 
>  #endif
> --

Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia