Re: [PATCH v6 06/30] PCI: Combine PCI domain and bus number in u32 arg

[Bjorn Helgaas]

On Mon, Mar 09, 2015 at 10:34:03AM +0800, Yijing Wang wrote:
> Currently, we use int type for bus number in
> pci_create_root_bus(), pci_scan_root_bus() and
> pci_scan_bus_legacy. Because PCI bus number
> always <= 255, so we could change the bus number
> argument type to u32, and combine PCI domain and
> bus number in one. 

This makes no sense.  Or rather, it only states the obvious: an 8-bit value
and a 16-bit value will both fit in a 32-bit value.  But it doesn't say
*why* you think it's a good idea to pass a single value that contains both
domain and bus numbers.  The obvious thing is to pass two separate values,
and you don't say why passing a single combined value is better.

Also see whitespace mistakes below.  I get a little testy when people don't
follow the whitespace convention of neighboring lines because if people are
sloppy about whitespace I assume they're sloppy about the code.

> Also add a domain member in
> pci_host_bridge to save domain number. Finally,
> we could eliminate lots of the platform specific
> pci_domain_nr() in the last of the series.
> 
> Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx>
> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> ---
>  drivers/pci/probe.c      |   16 +++++++++-------
>  include/linux/pci.h      |    7 ++++---
>  include/uapi/linux/pci.h |    3 +++
>  3 files changed, 16 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 187fa54..3d6befd 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1890,7 +1890,7 @@ void __weak pcibios_remove_bus(struct pci_bus *bus)
>  {
>  }
>  
> -struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
> +struct pci_bus *pci_create_root_bus(struct device *parent, u32 db,
>  		struct pci_ops *ops, void *sysdata, struct list_head *resources)
>  {
>  	int error;
> @@ -1901,6 +1901,7 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>  	resource_size_t offset;
>  	char bus_addr[64];
>  	char *fmt;
> +	u8	bus = PCI_BUSNUM(db);

Whitespace botch.

>  
>  	b = pci_alloc_bus(NULL);
>  	if (!b)
> @@ -1921,6 +1922,7 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>  	if (!bridge)
>  		goto err_out;
>  
> +	bridge->domain = PCI_DOMAIN(db);
>  	bridge->dev.parent = parent;
>  	bridge->dev.release = pci_release_host_bridge_dev;
>  	dev_set_name(&bridge->dev, "pci%04x:%02x", pci_domain_nr(b), bus);
> @@ -2058,7 +2060,7 @@ void pci_bus_release_busn_res(struct pci_bus *b)
>  			res, ret ? "can not be" : "is");
>  }
>  
> -struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
> +struct pci_bus *pci_scan_root_bus(struct device *parent, u32 db,
>  		struct pci_ops *ops, void *sysdata, struct list_head *resources)
>  {
>  	struct resource_entry *window;
> @@ -2072,15 +2074,15 @@ struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
>  			break;
>  		}
>  
> -	b = pci_create_root_bus(parent, bus, ops, sysdata, resources);
> +	b = pci_create_root_bus(parent, db, ops, sysdata, resources);
>  	if (!b)
>  		return NULL;
>  
>  	if (!found) {
>  		dev_info(&b->dev,
>  		 "No busn resource found for root bus, will use [bus %02x-ff]\n",
> -			bus);
> -		pci_bus_insert_busn_res(b, bus, 255);
> +			PCI_BUSNUM(db));
> +		pci_bus_insert_busn_res(b, PCI_BUSNUM(db), 255);
>  	}
>  
>  	max = pci_scan_child_bus(b);
> @@ -2092,7 +2094,7 @@ struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
>  }
>  EXPORT_SYMBOL(pci_scan_root_bus);
>  
> -struct pci_bus *pci_scan_bus(int bus, struct pci_ops *ops,
> +struct pci_bus *pci_scan_bus(u32 db, struct pci_ops *ops,
>  					void *sysdata)
>  {
>  	LIST_HEAD(resources);
> @@ -2101,7 +2103,7 @@ struct pci_bus *pci_scan_bus(int bus, struct pci_ops *ops,
>  	pci_add_resource(&resources, &ioport_resource);
>  	pci_add_resource(&resources, &iomem_resource);
>  	pci_add_resource(&resources, &busn_resource);
> -	b = pci_create_root_bus(NULL, bus, ops, sysdata, &resources);
> +	b = pci_create_root_bus(NULL, db, ops, sysdata, &resources);
>  	if (b) {
>  		pci_scan_child_bus(b);
>  	} else {
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 36effb8..8b3d245 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -401,6 +401,7 @@ static inline int pci_channel_offline(struct pci_dev *pdev)
>  }
>  
>  struct pci_host_bridge {
> +	u16	domain;

Please follow the existing whitespace convention, i.e., use a space, not a
tab, between "u16 domain".

>  	struct device dev;
>  	struct pci_bus *bus;		/* root bus */
>  	struct list_head windows;	/* resource_entry */
> @@ -769,14 +770,14 @@ void pcibios_bus_to_resource(struct pci_bus *bus, struct resource *res,
>  void pcibios_scan_specific_bus(int busn);
>  struct pci_bus *pci_find_bus(int domain, int busnr);
>  void pci_bus_add_devices(const struct pci_bus *bus);
> -struct pci_bus *pci_scan_bus(int bus, struct pci_ops *ops, void *sysdata);
> -struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
> +struct pci_bus *pci_scan_bus(u32 dombus, struct pci_ops *ops, void *sysdata);
> +struct pci_bus *pci_create_root_bus(struct device *parent, u32 dombus,
>  				    struct pci_ops *ops, void *sysdata,
>  				    struct list_head *resources);
>  int pci_bus_insert_busn_res(struct pci_bus *b, int bus, int busmax);
>  int pci_bus_update_busn_res_end(struct pci_bus *b, int busmax);
>  void pci_bus_release_busn_res(struct pci_bus *b);
> -struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
> +struct pci_bus *pci_scan_root_bus(struct device *parent, u32 dombus,
>  					     struct pci_ops *ops, void *sysdata,
>  					     struct list_head *resources);
>  struct pci_bus *pci_add_new_bus(struct pci_bus *parent, struct pci_dev *dev,
> diff --git a/include/uapi/linux/pci.h b/include/uapi/linux/pci.h
> index 3c292bc..89c6f15 100644
> --- a/include/uapi/linux/pci.h
> +++ b/include/uapi/linux/pci.h
> @@ -30,6 +30,9 @@
>  #define PCI_DEVFN(slot, func)	((((slot) & 0x1f) << 3) | ((func) & 0x07))
>  #define PCI_SLOT(devfn)		(((devfn) >> 3) & 0x1f)
>  #define PCI_FUNC(devfn)		((devfn) & 0x07)
> +#define PCI_DOMAIN(db)		((db) >> 16)
> +#define PCI_BUSNUM(db)		((db) & 0xffff)
> +#define PCI_DOMBUS(domain, bus)		(((domain) << 16) | (bus))
>  
>  /* Ioctls for /proc/bus/pci/X/Y nodes. */
>  #define PCIIOC_BASE		('P' << 24 | 'C' << 16 | 'I' << 8)
> -- 
> 1.7.1
> 
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