linux-imx

/*

 * helper functions for SG DMA video4linux capture buffers

 *

 * The functions expect the hardware being able to scatter gather

 * (i.e. the buffers are not linear in physical memory, but fragmented

 * into PAGE_SIZE chunks).  They also assume the driver does not need

 * to touch the video data.

 *

 * (c) 2007 Mauro Carvalho Chehab, <mchehab@kernel.org>

 *

 * Highly based on video-buf written originally by:

 * (c) 2001,02 Gerd Knorr <kraxel@bytesex.org>

 * (c) 2006 Mauro Carvalho Chehab, <mchehab@kernel.org>

 * (c) 2006 Ted Walther and John Sokol

 *

 * 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; either version 2

 */

​

#include <linux/init.h>

#include <linux/module.h>

#include <linux/moduleparam.h>

#include <linux/sched/mm.h>

#include <linux/slab.h>

#include <linux/interrupt.h>

​

#include <linux/dma-mapping.h>

#include <linux/vmalloc.h>

#include <linux/pagemap.h>

#include <linux/scatterlist.h>

#include <asm/page.h>

#include <asm/pgtable.h>

​

#include <media/videobuf-dma-sg.h>

​

#define MAGIC_DMABUF 0x19721112

#define MAGIC_SG_MEM 0x17890714

​

#define MAGIC_CHECK(is, should)                     \

    if (unlikely((is) != (should))) {               \

        printk(KERN_ERR "magic mismatch: %x (expected %x)\n",   \

                is, should);                \

        BUG();                          \

    }

​

static int debug;

module_param(debug, int, 0644);

​

MODULE_DESCRIPTION("helper module to manage video4linux dma sg buffers");

MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@kernel.org>");

MODULE_LICENSE("GPL");

​

#define dprintk(level, fmt, arg...)                 \

    if (debug >= level)                     \

        printk(KERN_DEBUG "vbuf-sg: " fmt , ## arg)

​

/* --------------------------------------------------------------------- */

​

/*

 * Return a scatterlist for some page-aligned vmalloc()'ed memory

 * block (NULL on errors).  Memory for the scatterlist is allocated

 * using kmalloc.  The caller must free the memory.