Re: [PATCH v7 4/6] pci: Introduce a domain number for pci_host_bridge.

[Arnd Bergmann <arnd@arndb.de>]

On Thursday 10 April 2014 07:50:52 Bjorn Helgaas wrote:
> On Thu, Apr 10, 2014 at 2:00 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > On Wednesday 09 April 2014 21:48:14 Bjorn Helgaas wrote:
> >> On Wed, Apr 9, 2014 at 7:27 PM, Liviu Dudau <liviu@dudau.co.uk> wrote:
> >> > On Wed, Apr 09, 2014 at 08:02:41AM -0600, Bjorn Helgaas wrote:
> >> >> >>   struct pci_host_bridge {
> >> >> >>     int domain;
> >> >> >>     int node;
> >> >> >>     struct device *dev;
> >> >> >>     struct pci_ops *ops;
> >> >> >>     struct list_head resources;
> >> >> >>     void *sysdata;
> >> >> >>     struct pci_bus *bus;  /* filled in by core, not by arch */
> >> >> >>     ... /* other existing contents managed by core */
> >> >> >>   };
> >> >> >>
> >> >> >>   struct pci_bus *pci_scan_host_bridge(struct pci_host_bridge *bridge);
> >> >> >
> 
> I'm not sure I'm following you; you mean the arch-specific sysdata
> structure would contain a pointer to struct pci_host_bridge?
> 
> I have to admit that I'm not up on how other subsystems handle this
> sort of abstraction.  Do you have any pointers to good examples that I
> can study?

What I mean is like this:

/* generic structure */
struct pci_host_bridge {
        int domain;
        int node;
        struct device *dev;
        struct pci_ops *ops; 
        struct list_head resources;
        struct pci_bus *bus;  /* filled in by core, not by arch */
        ... /* other existing contents managed by core */
};

/* arm specific structure */
struct pci_sys_data {
        char            io_res_name[12];
                                        /* Bridge swizzling                     */
        u8              (*swizzle)(struct pci_dev *, u8 *);
                                        /* IRQ mapping                          */
        int             (*map_irq)(const struct pci_dev *, u8, u8);
                                        /* Resource alignement requirements     */
        void            (*add_bus)(struct pci_bus *bus);
        void            (*remove_bus)(struct pci_bus *bus);
        void            *private_data;  /* platform controller private data     */

	/* not a pointer: */
	struct pci_host_bridge bridge;
};
static inline struct pci_sys_data *to_pci_sys_data(struct pci_host_bridge *bridge)
{
	return container_of(bridge, struct pci_sys_data, bridge);
}

/* arm specific, driver specific structure */
struct tegra_pcie {
        void __iomem *pads;
        void __iomem *afi;

        struct clk *pex_clk;
        struct clk *afi_clk;
        struct clk *pll_e;
        struct clk *cml_clk;

        struct tegra_msi msi;

        struct list_head ports;
        unsigned int num_ports;

	struct pci_sys_data sysdata;
};
static inline struct tegra_pcie *to_tegra_pcie(struct pci_sys_data *sysdata)
{
	return container_of(sysdata, struct tegra_pcie, sysdata);
}

This mirrors how we treat devices: a pci_device has an embedded device,
and so on, in other subsystems we can have multiple layers.

In this example, the tegra pcie driver then allocates its own tegra_pcie
structure, fills out the fields it needs, and registers it with the
ARM architecture code, passing just the pci_sys_data pointer. That function
in turn passes a pointer to the embedded pci_host_bridge down to the
generic code. Ideally we should try to eliminate the architecture specific
portion here, but that is a later step.

	Arnd