Re: [PATCH pciutils] lspci: Print buses of multibus PCI domain in ascending order

["Pali Rohár" <pali@kernel.org>]

On Monday 20 December 2021 20:53:49 Pali Rohár wrote:
> Currently PCI domains are printed in ascending order. Devices on each PCI
> bus are also printed in ascending order. PCI buses behind PCI-to-PCI
> bridges are also printed in ascending order.
> 
> But buses of PCI domain are currently printed in descending order because
> function new_bus() puts newly created bus at the beginning of linked list.
> 
> In most cases PCI domain contains only one (top level) bus, so in most
> cases it is not visible this inconsistency.
> 
> Multibus PCI domains (where PCI domain contains more independent top level
> PCI buses) are available on ARM devices.
> 
> This change fixes print order of multibus PCI domains, so also top level
> PCI buses are printed in ascending order, like PCI buses behind PCI-to-PCI
> bridges.
> ---
>  ls-tree.c | 10 +++++++---
>  lspci.h   |  2 +-
>  2 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/ls-tree.c b/ls-tree.c
> index aeb40870865e..17a95307b3fa 100644
> --- a/ls-tree.c
> +++ b/ls-tree.c
> @@ -12,7 +12,7 @@
>  
>  #include "lspci.h"
>  
> -struct bridge host_bridge = { NULL, NULL, NULL, NULL, 0, ~0, 0, ~0, NULL };
> +struct bridge host_bridge = { NULL, NULL, NULL, NULL, NULL, 0, ~0, 0, ~0, NULL };
>  
>  static struct bus *
>  find_bus(struct bridge *b, unsigned int domain, unsigned int n)
> @@ -31,11 +31,14 @@ new_bus(struct bridge *b, unsigned int domain, unsigned int n)
>    struct bus *bus = xmalloc(sizeof(struct bus));
>    bus->domain = domain;
>    bus->number = n;
> -  bus->sibling = b->first_bus;

Oops, this is a mistake. Default value for bus->sibling needs to be
explicitly set because xmalloc() wrapper does not return zero
initialized memory. So correct change for above line should be:

-  bus->sibling = b->first_bus;
+  bus->sibling = NULL;

>    bus->first_dev = NULL;
>    bus->last_dev = &bus->first_dev;
>    bus->parent_bridge = b;
> -  b->first_bus = bus;
> +  if (b->last_bus)
> +    b->last_bus->sibling = bus;
> +  b->last_bus = bus;
> +  if (!b->first_bus)
> +    b->first_bus = bus;
>    return bus;
>  }
>  
> @@ -101,6 +104,7 @@ grow_tree(void)
>  	  last_br = &b->chain;
>  	  b->next = b->child = NULL;
>  	  b->first_bus = NULL;
> +	  b->last_bus = NULL;
>  	  b->br_dev = d;
>  	  d->bridge = b;
>  	  pacc->debug("Tree: bridge %04x:%02x:%02x.%d: %02x -> %02x-%02x\n",
> diff --git a/lspci.h b/lspci.h
> index fefee5256423..352177fcce7b 100644
> --- a/lspci.h
> +++ b/lspci.h
> @@ -90,7 +90,7 @@ void show_kernel_cleanup(void);
>  struct bridge {
>    struct bridge *chain;			/* Single-linked list of bridges */
>    struct bridge *next, *child;		/* Tree of bridges */
> -  struct bus *first_bus;		/* List of buses connected to this bridge */
> +  struct bus *first_bus, *last_bus;	/* List of buses connected to this bridge */
>    unsigned int domain;
>    unsigned int primary, secondary, subordinate;	/* Bus numbers */
>    struct device *br_dev;
> -- 
> 2.20.1
>