Re: [PATCH v6 04/24] PCI/sysfs: Use BAR length in pci_llseek_resource() when attr->size is zero

Hello,

> The alternative would be separate llseek callbacks for both the legacy
> and resource attributes, which we can add if this would be the preference
> here.

If we were to do this, then it would be as follows:

  static loff_t pci_llseek_resource(struct file *filep,
                                    struct kobject *kobj,
                                    const struct bin_attribute *attr,
                                    loff_t offset, int whence)
  {
        struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
        int bar = (unsigned long)attr->private;

        return fixed_size_llseek(filep, offset, whence,
                                 pci_resource_len(pdev, bar));
  }

  static loff_t pci_llseek_resource_legacy(struct file *filep,
					   struct kobject *kobj __always_unused,
                                           const struct bin_attribute *attr,
                                           loff_t offset, int whence)
  {
        return fixed_size_llseek(filep, offset, whence, attr->size);
  }

Each callback would be placed within the corresponding #ifdef block, so one
for HAVE_PCI_MMAP or ARCH_GENERIC_PCI_MMAP_RESOURCE, and the other for the
legacy attributes, so behind the HAVE_PCI_LEGACY guard.

Note, the names need to be different, as some architectures offer both
type of resource files, like PowerPC, which defines both the HAVE_PCI_LEGACY
and HAVE_PCI_MMAP.

With this split, we can also drop the __maybe_unused annotation.

While I wanted to keep the changes to only what was needed for the
pci_llseek_resource() to cover both type of resources, it would be
also fine to have two distinct callbacks, too.

Thank you!

	Krzysztof