linux/drivers/media/common/videobuf2/frame_vector.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <linux/sched.h>

#include <media/frame_vector.h>

/**
 * get_vaddr_frames() - map virtual addresses to pfns
 * @start:	starting user address
 * @nr_frames:	number of pages / pfns from start to map
 * @write:	the mapped address has write permission
 * @vec:	structure which receives pages / pfns of the addresses mapped.
 *		It should have space for at least nr_frames entries.
 *
 * This function maps virtual addresses from @start and fills @vec structure
 * with page frame numbers or page pointers to corresponding pages (choice
 * depends on the type of the vma underlying the virtual address). If @start
 * belongs to a normal vma, the function grabs reference to each of the pages
 * to pin them in memory. If @start belongs to VM_IO | VM_PFNMAP vma, we don't
 * touch page structures and the caller must make sure pfns aren't reused for
 * anything else while he is using them.
 *
 * The function returns number of pages mapped which may be less than
 * @nr_frames. In particular we stop mapping if there are more vmas of
 * different type underlying the specified range of virtual addresses.
 * When the function isn't able to map a single page, it returns error.
 *
 * Note that get_vaddr_frames() cannot follow VM_IO mappings. It used
 * to be able to do that, but that could (racily) return non-refcounted
 * pfns.
 *
 * This function takes care of grabbing mmap_lock as necessary.
 */
int get_vaddr_frames(unsigned long start, unsigned int nr_frames, bool write,
		     struct frame_vector *vec)
{ … }
EXPORT_SYMBOL(…);

/**
 * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
 *			them
 * @vec:	frame vector to put
 *
 * Drop references to pages if get_vaddr_frames() acquired them. We also
 * invalidate the frame vector so that it is prepared for the next call into
 * get_vaddr_frames().
 */
void put_vaddr_frames(struct frame_vector *vec)
{ … }
EXPORT_SYMBOL(…);

/**
 * frame_vector_to_pages - convert frame vector to contain page pointers
 * @vec:	frame vector to convert
 *
 * Convert @vec to contain array of page pointers.  If the conversion is
 * successful, return 0. Otherwise return an error. Note that we do not grab
 * page references for the page structures.
 */
int frame_vector_to_pages(struct frame_vector *vec)
{ … }
EXPORT_SYMBOL(…);

/**
 * frame_vector_to_pfns - convert frame vector to contain pfns
 * @vec:	frame vector to convert
 *
 * Convert @vec to contain array of pfns.
 */
void frame_vector_to_pfns(struct frame_vector *vec)
{ … }
EXPORT_SYMBOL(…);

/**
 * frame_vector_create() - allocate & initialize structure for pinned pfns
 * @nr_frames:	number of pfns slots we should reserve
 *
 * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
 * pfns.
 */
struct frame_vector *frame_vector_create(unsigned int nr_frames)
{ … }
EXPORT_SYMBOL(…);

/**
 * frame_vector_destroy() - free memory allocated to carry frame vector
 * @vec:	Frame vector to free
 *
 * Free structure allocated by frame_vector_create() to carry frames.
 */
void frame_vector_destroy(struct frame_vector *vec)
{ … }
EXPORT_SYMBOL(…);