[media] vb2: Provide helpers for mapping virtual addresses

Provide simple helper functions to map virtual address range into an
array of pfns / pages.
Tested-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/v4l2-core/Kconfig

@@ -84,6 +84,7 @@ config VIDEOBUF2_CORE
 
 config VIDEOBUF2_MEMOPS
 	tristate
+	select FRAME_VECTOR
 
 config VIDEOBUF2_DMA_CONTIG
 	tristate

drivers/media/v4l2-core/videobuf2-memops.c

@@ -136,6 +136,64 @@ int vb2_get_contig_userptr(unsigned long vaddr, unsigned long size,
 }
 EXPORT_SYMBOL_GPL(vb2_get_contig_userptr);
 
+/**
+ * vb2_create_framevec() - map virtual addresses to pfns
+ * @start:	Virtual user address where we start mapping
+ * @length:	Length of a range to map
+ * @write:	Should we map for writing into the area
+ *
+ * This function allocates and fills in a vector with pfns corresponding to
+ * virtual address range passed in arguments. If pfns have corresponding pages,
+ * page references are also grabbed to pin pages in memory. The function
+ * returns pointer to the vector on success and error pointer in case of
+ * failure. Returned vector needs to be freed via vb2_destroy_pfnvec().
+ */
+struct frame_vector *vb2_create_framevec(unsigned long start,
+					 unsigned long length,
+					 bool write)
+{
+	int ret;
+	unsigned long first, last;
+	unsigned long nr;
+	struct frame_vector *vec;
+
+	first = start >> PAGE_SHIFT;
+	last = (start + length - 1) >> PAGE_SHIFT;
+	nr = last - first + 1;
+	vec = frame_vector_create(nr);
+	if (!vec)
+		return ERR_PTR(-ENOMEM);
+	ret = get_vaddr_frames(start, nr, write, 1, vec);
+	if (ret < 0)
+		goto out_destroy;
+	/* We accept only complete set of PFNs */
+	if (ret != nr) {
+		ret = -EFAULT;
+		goto out_release;
+	}
+	return vec;
+out_release:
+	put_vaddr_frames(vec);
+out_destroy:
+	frame_vector_destroy(vec);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(vb2_create_framevec);
+
+/**
+ * vb2_destroy_framevec() - release vector of mapped pfns
+ * @vec:	vector of pfns / pages to release
+ *
+ * This releases references to all pages in the vector @vec (if corresponding
+ * pfns are backed by pages) and frees the passed vector.
+ */
+void vb2_destroy_framevec(struct frame_vector *vec)
+{
+	put_vaddr_frames(vec);
+	frame_vector_destroy(vec);
+}
+EXPORT_SYMBOL(vb2_destroy_framevec);
+
 /**
  * vb2_common_vm_open() - increase refcount of the vma
  * @vma:	virtual memory region for the mapping

include/media/videobuf2-memops.h

@@ -15,6 +15,7 @@
 #define _MEDIA_VIDEOBUF2_MEMOPS_H
 
 #include <media/videobuf2-core.h>
+#include <linux/mm.h>
 
 /**
  * vb2_vmarea_handler - common vma refcount tracking handler
@@ -36,5 +37,9 @@ int vb2_get_contig_userptr(unsigned long vaddr, unsigned long size,
 struct vm_area_struct *vb2_get_vma(struct vm_area_struct *vma);
 void vb2_put_vma(struct vm_area_struct *vma);
 
+struct frame_vector *vb2_create_framevec(unsigned long start,
+					 unsigned long length,
+					 bool write);
+void vb2_destroy_framevec(struct frame_vector *vec);
 
 #endif