Re: [PATCH v6 1/4] PCI: Introduce pci_dev_for_each_resource()

[Bjorn Helgaas <helgaas@xxxxxxxxxx>]

Hi Andy and Mika,

I really like the improvements here.  They make the code read much
better.

On Mon, Mar 20, 2023 at 03:16:30PM +0200, Andy Shevchenko wrote:
> From: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> ...

>  static void fixup_winbond_82c105(struct pci_dev* dev)
>  {
> -     int i;
> +     struct resource *r;
>       unsigned int reg;
>  
>       if (!machine_is(pseries))
> @@ -251,14 +251,14 @@ static void fixup_winbond_82c105(struct pci_dev* dev)
>       /* Enable LEGIRQ to use INTC instead of ISA interrupts */
>       pci_write_config_dword(dev, 0x40, reg | (1<<11));
>  
> -     for (i = 0; i < DEVICE_COUNT_RESOURCE; ++i) {
> +     pci_dev_for_each_resource_p(dev, r) {
>               /* zap the 2nd function of the winbond chip */
> -             if (dev->resource[i].flags & IORESOURCE_IO
> -                 && dev->bus->number == 0 && dev->devfn == 0x81)
> -                     dev->resource[i].flags &= ~IORESOURCE_IO;
> -             if (dev->resource[i].start == 0 && dev->resource[i].end) {
> -                     dev->resource[i].flags = 0;
> -                     dev->resource[i].end = 0;
> +             if (dev->bus->number == 0 && dev->devfn == 0x81 &&
> +                 r->flags & IORESOURCE_IO)

This is a nice literal conversion, but it's kind of lame to test
bus->number and devfn *inside* the loop here, since they can't change
inside the loop.

> +                     r->flags &= ~IORESOURCE_IO;
> +             if (r->start == 0 && r->end) {
> +                     r->flags = 0;
> +                     r->end = 0;
>               }
>       }

>  #define pci_resource_len(dev,bar) \
>       ((pci_resource_end((dev), (bar)) == 0) ? 0 :    \
>                                                       \
> -      (pci_resource_end((dev), (bar)) -              \
> -       pci_resource_start((dev), (bar)) + 1))
> +      resource_size(pci_resource_n((dev), (bar))))

I like this change, but it's unrelated to pci_dev_for_each_resource()
and unmentioned in the commit log.

> +#define __pci_dev_for_each_resource(dev, res, __i, vartype)          \
> +     for (vartype __i = 0;                                           \
> +          res = pci_resource_n(dev, __i), __i < PCI_NUM_RESOURCES;   \
> +          __i++)
> +
> +#define pci_dev_for_each_resource(dev, res, i)                               
> \
> +       __pci_dev_for_each_resource(dev, res, i, )
> +
> +#define pci_dev_for_each_resource_p(dev, res)                                
> \
> +     __pci_dev_for_each_resource(dev, res, __i, unsigned int)

This series converts many cases to drop the iterator variable ("i"),
which is fantastic.

Several of the remaining places need the iterator variable only to
call pci_claim_resource(), which could be converted to take a "struct
resource *" directly without much trouble.

We don't have to do that pci_claim_resource() conversion now, but
since we're converging on the "(dev, res)" style, I think we should
reverse the names so we have something like:

  pci_dev_for_each_resource(dev, res)
  pci_dev_for_each_resource_idx(dev, res, i)

Not sure __pci_dev_for_each_resource() is worthwhile since it only
avoids repeating that single "for" statement, and passing in "vartype"
(sometimes empty to implicitly avoid the declaration) is a little
complicated to read.  I think it'd be easier to read like this:

  #define pci_dev_for_each_resource(dev, res)                      \
    for (unsigned int __i = 0;                                     \
         res = pci_resource_n(dev, __i), __i < PCI_NUM_RESOURCES;  \
         __i++)

  #define pci_dev_for_each_resource_idx(dev, res, idx)             \
    for (idx = 0;                                                  \
         res = pci_resource_n(dev, idx), idx < PCI_NUM_RESOURCES;  \
         idx++)

Bjorn