On ARM64, the MMU supports special memory attributes for device
memory/registers. Due to this we have pgprot_device() provided
by asm/pgtable.h of arch/arm64.
On architectures that do not have special MMU attribute for device
memory/registers, the asm-generic/pgtable.h maps pgprot_device()
to pgprot_noncached().
This patch introduces a new UIO mem region type UIO_MEM_DEVICE to
represent device registers/memory. The UIO device drivers should
prefer this new UIO mem region type for memory mapped device registers.
Signed-off-by: Anup Patel <anup.patel@xxxxxxxxxxxx>
---
drivers/uio/uio.c | 4 ++++
include/linux/uio_driver.h | 1 +
2 files changed, 5 insertions(+)
diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 0e53076..a00990c 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -663,6 +663,9 @@ static int uio_mmap_physical(struct vm_area_struct *vma, int memtype)
case UIO_MEM_PHYS_CACHE:
/* Do nothing. */
break;
+ case UIO_MEM_DEVICE:
+ vma->vm_page_prot = pgprot_device(vma->vm_page_prot);
+ break;
default:
return -EINVAL;
}
@@ -714,6 +717,7 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
switch (idev->info->mem[mi].memtype) {
case UIO_MEM_PHYS:
case UIO_MEM_PHYS_CACHE:
+ case UIO_MEM_DEVICE:
return uio_mmap_physical(vma, idev->info->mem[mi].memtype);
case UIO_MEM_LOGICAL:
case UIO_MEM_VIRTUAL:
diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
index 31359aee..7349f95 100644
--- a/include/linux/uio_driver.h
+++ b/include/linux/uio_driver.h
@@ -129,6 +129,7 @@ extern void uio_event_notify(struct uio_info *info);
#define UIO_MEM_LOGICAL 2
#define UIO_MEM_VIRTUAL 3
#define UIO_MEM_PHYS_CACHE 4
+#define UIO_MEM_DEVICE 5
/* defines for uio_port->porttype */
#define UIO_PORT_NONE 0
--
1.9.1
--
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