[PATCH RFC v1 3/6] swiotlb: introduce swiotlb_get_type() to calculate swiotlb buffer type

[Dongli Zhang]

This patch introduces swiotlb_get_type() in order to calculate which
swiotlb buffer the given DMA address is belong to.

This is to prepare to enable 64-bit swiotlb.

Cc: Joe Jin <joe.jin at oracle.com>
Signed-off-by: Dongli Zhang <dongli.zhang at oracle.com>
---
 include/linux/swiotlb.h | 14 ++++++++++++++
 kernel/dma/swiotlb.c    |  2 ++
 2 files changed, 16 insertions(+)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 777046cd4d1b..3d5980d77810 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -3,6 +3,7 @@
 #define __LINUX_SWIOTLB_H
 
 #include <linux/dma-direction.h>
+#include <linux/errno.h>
 #include <linux/init.h>
 #include <linux/types.h>
 #include <linux/limits.h>
@@ -23,6 +24,8 @@ enum swiotlb_t {
 	SWIOTLB_MAX,
 };
 
+extern int swiotlb_nr;
+
 /*
  * Maximum allowable number of contiguous slabs to map,
  * must be a power of 2.  What is the appropriate value ?
@@ -84,6 +87,17 @@ static inline bool is_swiotlb_buffer(phys_addr_t paddr)
 	       paddr < io_tlb_end[SWIOTLB_LO];
 }
 
+static inline int swiotlb_get_type(phys_addr_t paddr)
+{
+	int i;
+
+	for (i = 0; i < swiotlb_nr; i++)
+		if (paddr >= io_tlb_start[i] && paddr < io_tlb_end[i])
+			return i;
+
+	return -ENOENT;
+}
+
 void __init swiotlb_exit(void);
 unsigned int swiotlb_max_segment(void);
 size_t swiotlb_max_mapping_size(struct device *dev);
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 1fbb65daa2dd..c91d3d2c3936 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -109,6 +109,8 @@ static DEFINE_SPINLOCK(io_tlb_lock);
 
 static int late_alloc;
 
+int swiotlb_nr = 1;
+
 static int __init
 setup_io_tlb_npages(char *str)
 {
-- 
2.17.1