#include <linux/module.h>
 #include <linux/dma-mapping.h>
 #include "dma.h"

 #define BUFLEN (PAGE_SIZE)

 static void *source_log, *dest_log, *cb_log;
 static dma_addr_t source_io, dest_io, cb_io;
 static struct bcm2708_dma_cb *cb;
 static int channel;
 static dma_addr_t dma_reg;

 static int __init mod_init( void )
 {
     unsigned int irqs;

     /************************/
     /* Speicher reservieren */
     /************************/
     source_log=dma_alloc_coherent(NULL,BUFLEN,&source_io,
         GFP_KERNEL);
     if (!source_log) {
         printk(KERN_ERR "dma_alloc_coherent error source\n");
         return -EIO;
     }
     dest_log=dma_alloc_coherent(NULL,BUFLEN,&dest_io,GFP_KERNEL);
     if (!dest_log) {
         printk(KERN_ERR "dma_alloc_coherent error dest\n");
         goto free_source;
     }
     cb_log=dma_alloc_coherent(NULL,sizeof(struct bcm2708_dma_cb),
         &cb_io, GFP_KERNEL);
     if (!cb_log) {
         printk(KERN_ERR "dma_alloc_coherent error cb\n");
         goto free_dest;
     }
     printk("SOURCE: log-addr: %p bus-addr: %p phys_addr: %p\n",
         source_log, (char *)source_io,
         (char *)virt_to_phys(source_log));
     printk("DEST:   log-addr: %p bus-addr: %p phys_addr: %p\n",
         dest_log,(char *)dest_io,(char *)virt_to_phys(dest_log));
     printk("CB:     log-addr: %p bus-addr: %p phys_addr: %p\n",
         cb_log, (char *)cb_io, (char *)virt_to_phys(cb_log));
     memcpy( source_log, "Hello World", strlen("Hello World")+1);
     memcpy( dest_log,"not yet copied",strlen("not yet copied")+1);

     /***********************/
     /* DMA-Kanal aufsetzen */
     /***********************/
     channel = bcm_dma_chan_alloc( BCM_DMA_FEATURE_NORMAL,
         (void *)&dma_reg, &irqs );
     printk("channel: %d dma_reg: %p irqs: %x\n",channel,
         (void*)dma_reg,irqs);

     cb = (struct bcm2708_dma_cb *) cb_log;

     cb->info= BCM2708_DMA_S_INC | BCM2708_DMA_D_INC;
     cb->src = (unsigned long) source_io;
     cb->dst = (unsigned long) dest_io;
     cb->length = BUFLEN;
     cb->stride = 0;
     cb->next = 0;

     /****************/
     /* DMA-Transfer */
     /****************/
     printk("ZIEL VORHER  %p: %s\n", dest_log, (char *)dest_log);
     bcm_dma_start( (void*)dma_reg, cb_io );
     bcm_dma_wait_idle( (void*)dma_reg );
     printk("ZIEL NACHHER %p: %s\n", dest_log, (char *)dest_log);
     return 0;
 free_dest:
     dma_free_coherent(NULL, BUFLEN, dest_log, dest_io );
 free_source:
     dma_free_coherent(NULL, BUFLEN, source_log, source_io);
     if (channel) bcm_dma_chan_free(channel);
     return -EIO;
 }

 static void __exit mod_exit( void )
 {
     printk("freeing dma-ressources\n");
     dma_free_coherent(NULL, BUFLEN, dest_log, dest_io );
     dma_free_coherent(NULL, BUFLEN, source_log, source_io);
     dma_free_coherent(NULL, sizeof(struct bcm2708_dma_cb),
         cb_log, cb_io);
     if (channel) bcm_dma_chan_free(channel);
     return;
 }

 module_init( mod_init );
 module_exit( mod_exit );
 MODULE_LICENSE("GPL");