drivers/scsi/scsi_lib_dma.c

   1 /*
   2  * SCSI library functions depending on DMA
   3  */
   4
   5 #include <linux/blkdev.h>
   6 #include <linux/device.h>
   7 #include <linux/kernel.h>
   8
   9 #include <scsi/scsi.h>
  10 #include <scsi/scsi_cmnd.h>
  11 #include <scsi/scsi_device.h>
  12 #include <scsi/scsi_host.h>
  13
  14 /**
  15  * scsi_dma_map - perform DMA mapping against command's sg lists
  16  * @cmd:        scsi command
  17  *
  18  * Returns the number of sg lists actually used, zero if the sg lists
  19  * is NULL, or -ENOMEM if the mapping failed.
  20  */
  21 int scsi_dma_map(struct scsi_cmnd *cmd)
  22 {
  23         int nseg = 0;
  24
  25         if (scsi_sg_count(cmd)) {
  26                 struct device *dev = cmd->device->host->dma_dev;
  27
  28                 nseg = dma_map_sg(dev, scsi_sglist(cmd), scsi_sg_count(cmd),
  29                                   cmd->sc_data_direction);
  30                 if (unlikely(!nseg))
  31                         return -ENOMEM;
  32         }
  33         return nseg;
  34 }
  35 EXPORT_SYMBOL(scsi_dma_map);
  36
  37 /**
  38  * scsi_dma_unmap - unmap command's sg lists mapped by scsi_dma_map
  39  * @cmd:        scsi command
  40  */
  41 void scsi_dma_unmap(struct scsi_cmnd *cmd)
  42 {
  43         if (scsi_sg_count(cmd)) {
  44                 struct device *dev = cmd->device->host->dma_dev;
  45
  46                 dma_unmap_sg(dev, scsi_sglist(cmd), scsi_sg_count(cmd),
  47                              cmd->sc_data_direction);
  48         }
  49 }
  50 EXPORT_SYMBOL(scsi_dma_unmap);