linux/drivers/media/video/videobuf2-dma-sg.c
Jonathan Corbet 297875b6a1 [media] videobuf2: Do not unconditionally map S/G buffers into kernel space
The one in-tree videobuf2-dma-sg driver (mmp-camera) has no need for a
kernel-space mapping of the buffers; one suspects that most other drivers
would not either.  The videobuf2-dma-sg module does the right thing if
buf->vaddr == NULL - it maps the buffer on demand if somebody needs it.  So
let's not map the buffer at allocation time; that will save a little CPU
time and a lot of address space in the vmalloc range.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
2011-09-03 10:57:33 -03:00

285 lines
6.8 KiB
C

/*
* videobuf2-dma-sg.c - dma scatter/gather memory allocator for videobuf2
*
* Copyright (C) 2010 Samsung Electronics
*
* Author: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/scatterlist.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <media/videobuf2-core.h>
#include <media/videobuf2-memops.h>
#include <media/videobuf2-dma-sg.h>
struct vb2_dma_sg_buf {
void *vaddr;
struct page **pages;
int write;
int offset;
struct vb2_dma_sg_desc sg_desc;
atomic_t refcount;
struct vb2_vmarea_handler handler;
};
static void vb2_dma_sg_put(void *buf_priv);
static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned long size)
{
struct vb2_dma_sg_buf *buf;
int i;
buf = kzalloc(sizeof *buf, GFP_KERNEL);
if (!buf)
return NULL;
buf->vaddr = NULL;
buf->write = 0;
buf->offset = 0;
buf->sg_desc.size = size;
buf->sg_desc.num_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
buf->sg_desc.sglist = vzalloc(buf->sg_desc.num_pages *
sizeof(*buf->sg_desc.sglist));
if (!buf->sg_desc.sglist)
goto fail_sglist_alloc;
sg_init_table(buf->sg_desc.sglist, buf->sg_desc.num_pages);
buf->pages = kzalloc(buf->sg_desc.num_pages * sizeof(struct page *),
GFP_KERNEL);
if (!buf->pages)
goto fail_pages_array_alloc;
for (i = 0; i < buf->sg_desc.num_pages; ++i) {
buf->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN);
if (NULL == buf->pages[i])
goto fail_pages_alloc;
sg_set_page(&buf->sg_desc.sglist[i],
buf->pages[i], PAGE_SIZE, 0);
}
buf->handler.refcount = &buf->refcount;
buf->handler.put = vb2_dma_sg_put;
buf->handler.arg = buf;
atomic_inc(&buf->refcount);
printk(KERN_DEBUG "%s: Allocated buffer of %d pages\n",
__func__, buf->sg_desc.num_pages);
return buf;
fail_pages_alloc:
while (--i >= 0)
__free_page(buf->pages[i]);
kfree(buf->pages);
fail_pages_array_alloc:
vfree(buf->sg_desc.sglist);
fail_sglist_alloc:
kfree(buf);
return NULL;
}
static void vb2_dma_sg_put(void *buf_priv)
{
struct vb2_dma_sg_buf *buf = buf_priv;
int i = buf->sg_desc.num_pages;
if (atomic_dec_and_test(&buf->refcount)) {
printk(KERN_DEBUG "%s: Freeing buffer of %d pages\n", __func__,
buf->sg_desc.num_pages);
if (buf->vaddr)
vm_unmap_ram(buf->vaddr, buf->sg_desc.num_pages);
vfree(buf->sg_desc.sglist);
while (--i >= 0)
__free_page(buf->pages[i]);
kfree(buf->pages);
kfree(buf);
}
}
static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
unsigned long size, int write)
{
struct vb2_dma_sg_buf *buf;
unsigned long first, last;
int num_pages_from_user, i;
buf = kzalloc(sizeof *buf, GFP_KERNEL);
if (!buf)
return NULL;
buf->vaddr = NULL;
buf->write = write;
buf->offset = vaddr & ~PAGE_MASK;
buf->sg_desc.size = size;
first = (vaddr & PAGE_MASK) >> PAGE_SHIFT;
last = ((vaddr + size - 1) & PAGE_MASK) >> PAGE_SHIFT;
buf->sg_desc.num_pages = last - first + 1;
buf->sg_desc.sglist = vzalloc(
buf->sg_desc.num_pages * sizeof(*buf->sg_desc.sglist));
if (!buf->sg_desc.sglist)
goto userptr_fail_sglist_alloc;
sg_init_table(buf->sg_desc.sglist, buf->sg_desc.num_pages);
buf->pages = kzalloc(buf->sg_desc.num_pages * sizeof(struct page *),
GFP_KERNEL);
if (!buf->pages)
goto userptr_fail_pages_array_alloc;
down_read(&current->mm->mmap_sem);
num_pages_from_user = get_user_pages(current, current->mm,
vaddr & PAGE_MASK,
buf->sg_desc.num_pages,
write,
1, /* force */
buf->pages,
NULL);
up_read(&current->mm->mmap_sem);
if (num_pages_from_user != buf->sg_desc.num_pages)
goto userptr_fail_get_user_pages;
sg_set_page(&buf->sg_desc.sglist[0], buf->pages[0],
PAGE_SIZE - buf->offset, buf->offset);
size -= PAGE_SIZE - buf->offset;
for (i = 1; i < buf->sg_desc.num_pages; ++i) {
sg_set_page(&buf->sg_desc.sglist[i], buf->pages[i],
min_t(size_t, PAGE_SIZE, size), 0);
size -= min_t(size_t, PAGE_SIZE, size);
}
return buf;
userptr_fail_get_user_pages:
printk(KERN_DEBUG "get_user_pages requested/got: %d/%d]\n",
num_pages_from_user, buf->sg_desc.num_pages);
while (--num_pages_from_user >= 0)
put_page(buf->pages[num_pages_from_user]);
kfree(buf->pages);
userptr_fail_pages_array_alloc:
vfree(buf->sg_desc.sglist);
userptr_fail_sglist_alloc:
kfree(buf);
return NULL;
}
/*
* @put_userptr: inform the allocator that a USERPTR buffer will no longer
* be used
*/
static void vb2_dma_sg_put_userptr(void *buf_priv)
{
struct vb2_dma_sg_buf *buf = buf_priv;
int i = buf->sg_desc.num_pages;
printk(KERN_DEBUG "%s: Releasing userspace buffer of %d pages\n",
__func__, buf->sg_desc.num_pages);
if (buf->vaddr)
vm_unmap_ram(buf->vaddr, buf->sg_desc.num_pages);
while (--i >= 0) {
if (buf->write)
set_page_dirty_lock(buf->pages[i]);
put_page(buf->pages[i]);
}
vfree(buf->sg_desc.sglist);
kfree(buf->pages);
kfree(buf);
}
static void *vb2_dma_sg_vaddr(void *buf_priv)
{
struct vb2_dma_sg_buf *buf = buf_priv;
BUG_ON(!buf);
if (!buf->vaddr)
buf->vaddr = vm_map_ram(buf->pages,
buf->sg_desc.num_pages,
-1,
PAGE_KERNEL);
/* add offset in case userptr is not page-aligned */
return buf->vaddr + buf->offset;
}
static unsigned int vb2_dma_sg_num_users(void *buf_priv)
{
struct vb2_dma_sg_buf *buf = buf_priv;
return atomic_read(&buf->refcount);
}
static int vb2_dma_sg_mmap(void *buf_priv, struct vm_area_struct *vma)
{
struct vb2_dma_sg_buf *buf = buf_priv;
unsigned long uaddr = vma->vm_start;
unsigned long usize = vma->vm_end - vma->vm_start;
int i = 0;
if (!buf) {
printk(KERN_ERR "No memory to map\n");
return -EINVAL;
}
do {
int ret;
ret = vm_insert_page(vma, uaddr, buf->pages[i++]);
if (ret) {
printk(KERN_ERR "Remapping memory, error: %d\n", ret);
return ret;
}
uaddr += PAGE_SIZE;
usize -= PAGE_SIZE;
} while (usize > 0);
/*
* Use common vm_area operations to track buffer refcount.
*/
vma->vm_private_data = &buf->handler;
vma->vm_ops = &vb2_common_vm_ops;
vma->vm_ops->open(vma);
return 0;
}
static void *vb2_dma_sg_cookie(void *buf_priv)
{
struct vb2_dma_sg_buf *buf = buf_priv;
return &buf->sg_desc;
}
const struct vb2_mem_ops vb2_dma_sg_memops = {
.alloc = vb2_dma_sg_alloc,
.put = vb2_dma_sg_put,
.get_userptr = vb2_dma_sg_get_userptr,
.put_userptr = vb2_dma_sg_put_userptr,
.vaddr = vb2_dma_sg_vaddr,
.mmap = vb2_dma_sg_mmap,
.num_users = vb2_dma_sg_num_users,
.cookie = vb2_dma_sg_cookie,
};
EXPORT_SYMBOL_GPL(vb2_dma_sg_memops);
MODULE_DESCRIPTION("dma scatter/gather memory handling routines for videobuf2");
MODULE_AUTHOR("Andrzej Pietrasiewicz");
MODULE_LICENSE("GPL");