/*
   * Implement the default iomap interfaces
   *
   * (C) Copyright 2004 Linus Torvalds
   */
  #include <linux/pci.h>
  #include <linux/io.h>
  
  #include <linux/export.h>
  
  #ifdef CONFIG_PCI
  /**
   * pci_iomap - create a virtual mapping cookie for a PCI BAR
   * @dev: PCI device that owns the BAR
   * @bar: BAR number
   * @maxlen: length of the memory to map
   *
   * Using this function you will get a __iomem address to your device BAR.
   * You can access it using ioread*() and iowrite*(). These functions hide
   * the details if this is a MMIO or PIO address space and will just do what
   * you expect from them in the correct way.
   *
   * @maxlen specifies the maximum length to map. If you want to get access to
   * the complete BAR without checking for its length first, pass %0 here.
   * */
  void __iomem *pci_iomap(struct pci_dev *dev, int bar, unsigned long maxlen)
  {
  	resource_size_t start = pci_resource_start(dev, bar);
  	resource_size_t len = pci_resource_len(dev, bar);
  	unsigned long flags = pci_resource_flags(dev, bar);
  
  	if (!len || !start)
  		return NULL;
  	if (maxlen && len > maxlen)
  		len = maxlen;
  	if (flags & IORESOURCE_IO)
  		return ioport_map(start, len);
  	if (flags & IORESOURCE_MEM) {
  		if (flags & IORESOURCE_CACHEABLE)
  			return ioremap(start, len);
  		return ioremap_nocache(start, len);
  	}
  	/* What? */
  	return NULL;
  }
  
  EXPORT_SYMBOL(pci_iomap);
  #endif /* CONFIG_PCI */