/* * Example showing how to pin down a range of virtual pages from user-space * to be able to do for example DMA directly into them. * * It is necessary because the pages the virtual pointers reference, might * not exist in memory (could be mapped to the zero-page, filemapped etc) * and DMA cannot trigger the MMU to force them in (and would have time  * contraints making it impossible to wait for it anyway). * * Author:  Bjorn Wesen * * $Log: kiobuftest.c,v $ * Revision 1.2  2001/02/27 13:52:50  bjornw * malloc.h -> slab.h * * Revision 1.1  2001/01/19 15:57:49  bjornw * Example of how to do direct HW -> user-mode DMA * * */#include <linux/module.h>#include <linux/sched.h>#include <linux/slab.h>#include <linux/errno.h>#include <linux/kernel.h>#include <linux/fs.h>#include <linux/string.h>#include <linux/init.h>#include <linux/mm.h>#include <linux/iobuf.h>#define KIOBUFTEST_MAJOR 124  /* in the local range, experimental */static ssize_tkiobuf_read(struct file *filp, char *buf, size_t len, loff_t *ppos){     struct kiobuf *iobuf;     int res, i;      /* Make a kiobuf that maps the entire length the reader has given      * us      */     res = alloc_kiovec(1, &iobuf);     if (res)	     return res;          if((res = map_user_kiobuf(READ, iobuf, (unsigned long)buf, len))) {	     printk("map_user_kiobuf failed, return %d\n", res);	     return res;     }     /* At this point, the virtual area buf[0] -> buf[len-1] will      * have corresponding pages mapped in physical memory and locked      * until we unmap the kiobuf. They cannot be swapped out or moved      * around.      */     printk("nr_pages == %d\noffset == %d\nlength == %d\n",	    iobuf->nr_pages, iobuf->offset, iobuf->length);     for(i = 0; i < iobuf->nr_pages; i++) {	     printk("page_add(maplist[%d]) == 0x%x\n", i,		    page_address(iobuf->maplist[i]));     }     /* This is the place to create the necessary scatter-gather vector      * for the DMA using the iobuf->maplist array and page_address      * (don't forget __pa if the DMA needs the actual physical DRAM address)      * and run it.      */     /* Release the mapping and exit */     unmap_kiobuf(iobuf); /* The unlock_kiobuf is implicit here */     return len;}static struct file_operations kiobuf_fops = {	owner:    THIS_MODULE,	read:     kiobuf_read};static int __initkiobuftest_init(void){	int res;	/* register char device */	res = register_chrdev(KIOBUFTEST_MAJOR, "kiobuftest", &kiobuf_fops);	if(res < 0) {		printk(KERN_ERR "kiobuftest: couldn't get a major number.\n");		return res;	}	printk("Initializing kiobuf-test device\n");}module_init(kiobuftest_init);