Re: [PATCH] Clarify pci_iomap() usage for MMIO-only devices

[Jeff Garzik <jeff@garzik.org>]

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Linus Torvalds wrote:
> Why do people insist on 
> using the old interfaces (and matching them with the new setup)?


readl/writel is [slightly] faster, and possibility of using even-write 
__raw_writel() exists, in the old interface...

  ...but pci_iomap() is a bus-friendly wrapper that handles a few checks 
and function calls for you, even if you know your device is always MMIO.

A new pci_mmio_map() helper, to be used with 100% MMIO hardware, might 
help eliminate confusion.

	Jeff



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diff --git a/include/asm-generic/iomap.h b/include/asm-generic/iomap.h
index cde592f..69e5390 100644
--- a/include/asm-generic/iomap.h
+++ b/include/asm-generic/iomap.h
@@ -63,6 +63,7 @@ extern void ioport_unmap(void __iomem *);
 /* Create a virtual mapping cookie for a PCI BAR (memory or IO) */
 struct pci_dev;
 extern void __iomem *pci_iomap(struct pci_dev *dev, int bar, unsigned long max);
+extern void __iomem *pci_mmio_map(struct pci_dev *dev, int bar, unsigned long max);
 extern void pci_iounmap(struct pci_dev *dev, void __iomem *);
 
 #endif
diff --git a/lib/iomap.c b/lib/iomap.c
index 864f2ec..c87d7f3 100644
--- a/lib/iomap.c
+++ b/lib/iomap.c
@@ -275,9 +275,32 @@ void __iomem *pci_iomap(struct pci_dev *dev, int bar, unsigned long maxlen)
 	return NULL;
 }
 
+/* for people who wish to use readl/writel exclusively */
+void __iomem *pci_mmio_map(struct pci_dev *dev, int bar, unsigned long maxlen)
+{
+	unsigned long start = pci_resource_start(dev, bar);
+	unsigned long 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 NULL;
+	if (flags & IORESOURCE_MEM) {
+		if (flags & IORESOURCE_CACHEABLE)
+			return ioremap(start, len);
+		return ioremap_nocache(start, len);
+	}
+	/* What? */
+	return NULL;
+}
+
 void pci_iounmap(struct pci_dev *dev, void __iomem * addr)
 {
 	IO_COND(addr, /* nothing */, iounmap(addr));
 }
 EXPORT_SYMBOL(pci_iomap);
+EXPORT_SYMBOL(pci_mmio_map);
 EXPORT_SYMBOL(pci_iounmap);