[PATCH 1/3] uio: introduce UIO_DMA_COHERENT type

Chris Leech
2023-09-29T17:01:45Z

Add a UIO memtype specificially for sharing dma_alloc_coherent
memory with userspace, backed by dma_mmap_coherent.

Signed-off-by: Chris Leech <cleech@redhat.com>
---
drivers/uio/uio.c | 34 ++++++++++++++++++++++++++++++++++
include/linux/uio_driver.h | 12 ++++++++++--
2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 62082d64ece0..f8f1f7ba6378 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -24,6 +24,7 @@
#include <linux/kobject.h>
#include <linux/cdev.h>
#include <linux/uio_driver.h>
+#include <linux/dma-mapping.h>

#define UIO_MAX_DEVICES (1U << MINORBITS)

@@ -759,6 +760,36 @@ static int uio_mmap_physical(struct vm_area_struct *vma)
vma->vm_page_prot);
}

+static int uio_mmap_dma_coherent(struct vm_area_struct *vma)
+{
+ struct uio_device *idev = vma->vm_private_data;
+ int mi = uio_find_mem_index(vma);
+ struct uio_mem *mem;
+ int rc;
+
+ if (mi < 0)
+ return -EINVAL;
+ mem = idev->info->mem + mi;
+
+ if (mem->dma_addr & ~PAGE_MASK)
+ return -ENODEV;
+ if (vma->vm_end - vma->vm_start > mem->size)
+ return -EINVAL;
+
+ /*
+ * UIO uses offset to index into the maps for a device.
+ * We need to clear vm_pgoff for dma_mmap_coherent.
+ */
+ vma->vm_pgoff = 0;
+ rc = dma_mmap_coherent(mem->dma_device,
+ vma,
+ mem->virtual_addr,
+ mem->dma_addr,
+ vma->vm_end - vma->vm_start);
+ vma->vm_pgoff = mi;
+ return rc;
+}
+
static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
{
struct uio_listener *listener = filep->private_data;
@@ -806,6 +837,9 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
case UIO_MEM_VIRTUAL:
ret = uio_mmap_logical(vma);
break;
+ case UIO_MEM_DMA_COHERENT:
+ ret = uio_mmap_dma_coherent(vma);
+ break;
default:
ret = -EINVAL;
}
diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
index 47c5962b876b..ede58e984658 100644
--- a/include/linux/uio_driver.h
+++ b/include/linux/uio_driver.h
@@ -36,11 +36,18 @@ struct uio_map;
*/
struct uio_mem {
const char *name;
- phys_addr_t addr;
+ union {
+ phys_addr_t addr;
+ dma_addr_t dma_addr;
+ };
unsigned long offs;
resource_size_t size;
int memtype;
- void __iomem *internal_addr;
+ union {
+ void __iomem *internal_addr;
+ void *virtual_addr;
+ };
+ struct device *dma_device;
struct uio_map *map;
};

@@ -158,6 +165,7 @@ extern int __must_check
#define UIO_MEM_LOGICAL 2
#define UIO_MEM_VIRTUAL 3
#define UIO_MEM_IOVA 4
+#define UIO_MEM_DMA_COHERENT 5

/* defines for uio_port->porttype */
#define UIO_PORT_NONE 0
--
2.41.0