[PATCH v2 3/5] mm: ioremap: Add arch_ioremap/iounmap()

[Kefeng Wang]

Add special hook for architecture to verify addr, size and prot
or setup when ioremap() or iounmap(), which will make the generic
ioremap more useful.

  arch_ioremap() return a 'void __iomem *',
    - IS_ERR means return an error
    - NULL means continue to remap
    - a non-NULL, non-IS_ERR pointer is directly returned
  arch_iounmap() return a int value,
    - 0 means continue to vunmap
    - error code means skip vunmap and return directly

Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
 include/asm-generic/io.h | 14 ++++++++++++++
 mm/ioremap.c             | 14 +++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index e6ffa2519f08..f2f9aeedb5e8 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -964,6 +964,20 @@ static inline void iounmap(volatile void __iomem *addr)
 #elif defined(CONFIG_GENERIC_IOREMAP)
 #include <linux/pgtable.h>
 
+#ifndef arch_ioremap
+static inline void __iomem *arch_ioremap(phys_addr_t phys_addr, size_t size, unsigned long prot)
+{
+	return NULL;
+}
+#endif
+
+#ifndef arch_iounmap
+static inline int arch_iounmap(void __iomem *addr)
+{
+	return 0;
+}
+#endif
+
 void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, unsigned long prot);
 void iounmap(volatile void __iomem *addr);
 
diff --git a/mm/ioremap.c b/mm/ioremap.c
index 7cb9996b0c12..de5a2e899e14 100644
--- a/mm/ioremap.c
+++ b/mm/ioremap.c
@@ -16,6 +16,7 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, unsigned long pro
 	unsigned long offset, vaddr;
 	phys_addr_t last_addr;
 	struct vm_struct *area;
+	void __iomem *base;
 
 	/* Disallow wrap-around or zero size */
 	last_addr = phys_addr + size - 1;
@@ -27,6 +28,12 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, unsigned long pro
 	phys_addr -= offset;
 	size = PAGE_ALIGN(size + offset);
 
+	base = arch_ioremap(phys_addr, size, prot);
+	if (IS_ERR(base))
+		return NULL;
+	else if (base)
+		return base;
+
 	area = get_vm_area_caller(size, VM_IOREMAP,
 			__builtin_return_address(0));
 	if (!area)
@@ -45,6 +52,11 @@ EXPORT_SYMBOL(ioremap_prot);
 
 void iounmap(volatile void __iomem *addr)
 {
-	vunmap((void *)((unsigned long)addr & PAGE_MASK));
+	void *vaddr = (void *)((unsigned long)addr & PAGE_MASK);
+
+	if (arch_iounmap(vaddr))
+		return;
+
+	vunmap(vaddr);
 }
 EXPORT_SYMBOL(iounmap);
-- 
2.35.3