[PATCH v8 3/9] pci: Introduce pci_register_io_range() helper function.

On Wed, Jul 02, 2014 at 01:38:04PM +0100, Arnd Bergmann wrote:

Some more detailed comments now

On Tuesday 01 July 2014 19:43:28 Liviu Dudau wrote:

quoted

+/*
+ * Record the PCI IO range (expressed as CPU physical address + size).
+ * Return a negative value if an error has occured, zero otherwise
+ */
+int __weak pci_register_io_range(phys_addr_t addr, resource_size_t size)
+{
+#ifdef PCI_IOBASE
+       struct io_range *res;

I was confused by the variable naming here: A variable named 'res' is
normally a 'struct resource'. Maybe better call this 'range'.

quoted

+       resource_size_t allocated_size = 0;
+
+       /* check if the range hasn't been previously recorded */
+       list_for_each_entry(res, &io_range_list, list) {
+               if (addr >= res->start && addr + size <= res->start + size)
+                       return 0;
+               allocated_size += res->size;
+       }

A spin_lock around the list lookup should be sufficient to get around
the race that Will mentioned.

quoted

+       /* range not registed yet, check for available space */
+       if (allocated_size + size - 1 > IO_SPACE_LIMIT)
+               return -E2BIG;

It might be better to limit the size to 64K if it doesn't fit at first.

Thanks Arnd for review. Will update and post a new patch soon if I don't
get any other comments.

Best regards,
Liviu

	Arnd

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