[SCSI] don't build scsi_dma_{map,unmap} for !HAS_DMA

With

dma-mapping-prevent-dma-dependent-code-from-linking-on.patch

scsi fails to build on !HAS_DMA architectures:

drivers/built-in.o(.text+0x20af6): In function `scsi_dma_map':
: undefined reference to `dma_map_sg'
drivers/built-in.o(.text+0x20b5c): In function `scsi_dma_unmap':
: undefined reference to `dma_unmap_sg'

I split those functions out into a new file. Builds on s390 and i386.

Move scsi_dma_{map,unmap} into scsi_lib_dma.c which is only build if
HAS_DMA is set.

Signed-off-by: Cornelia Huck <[e-mail]>
Cc: Martin Schwidefsky <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: James Bottomley <[e-mail]>
Cc: Jeff Garzik <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: Dan Williams <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/Kconfig

···
 config SCSI
 	tristate "SCSI device support"
 	depends on BLOCK
+	select SCSI_DMA if HAS_DMA
 	---help---
 	  If you want to use a SCSI hard disk, SCSI tape drive, SCSI CD-ROM or
 	  any other SCSI device under Linux, say Y and make sure that you know
···
 
 	  However, do not compile this as a module if your root file system
 	  (the one containing the directory /) is located on a SCSI device.
+
+config SCSI_DMA
+	bool
+	default n
 
 config SCSI_TGT
 	tristate "SCSI target support"

drivers/scsi/Makefile

···
 obj-$(CONFIG_SCSI_WAIT_SCAN)	+= scsi_wait_scan.o
 
 scsi_mod-y			+= scsi.o hosts.o scsi_ioctl.o constants.o \
-				   scsicam.o scsi_error.o scsi_lib.o \
-				   scsi_scan.o scsi_sysfs.o \
-				   scsi_devinfo.o
+				   scsicam.o scsi_error.o scsi_lib.o
+scsi_mod-$(CONFIG_SCSI_DMA)	+= scsi_lib_dma.o
+scsi_mod-y			+= scsi_scan.o scsi_sysfs.o scsi_devinfo.o
 scsi_mod-$(CONFIG_SCSI_NETLINK)	+= scsi_netlink.o
 scsi_mod-$(CONFIG_SYSCTL)	+= scsi_sysctl.o
 scsi_mod-$(CONFIG_SCSI_PROC_FS)	+= scsi_proc.o

drivers/scsi/scsi_lib.c

···
 	kunmap_atomic(virt, KM_BIO_SRC_IRQ);
 }
 EXPORT_SYMBOL(scsi_kunmap_atomic_sg);
-
-/**
- * scsi_dma_map - perform DMA mapping against command's sg lists
- * @cmd:	scsi command
- *
- * Returns the number of sg lists actually used, zero if the sg lists
- * is NULL, or -ENOMEM if the mapping failed.
- */
-int scsi_dma_map(struct scsi_cmnd *cmd)
-{
-	int nseg = 0;
-
-	if (scsi_sg_count(cmd)) {
-		struct device *dev = cmd->device->host->shost_gendev.parent;
-
-		nseg = dma_map_sg(dev, scsi_sglist(cmd), scsi_sg_count(cmd),
-				  cmd->sc_data_direction);
-		if (unlikely(!nseg))
-			return -ENOMEM;
-	}
-	return nseg;
-}
-EXPORT_SYMBOL(scsi_dma_map);
-
-/**
- * scsi_dma_unmap - unmap command's sg lists mapped by scsi_dma_map
- * @cmd:	scsi command
- */
-void scsi_dma_unmap(struct scsi_cmnd *cmd)
-{
-	if (scsi_sg_count(cmd)) {
-		struct device *dev = cmd->device->host->shost_gendev.parent;
-
-		dma_unmap_sg(dev, scsi_sglist(cmd), scsi_sg_count(cmd),
-			     cmd->sc_data_direction);
-	}
-}
-EXPORT_SYMBOL(scsi_dma_unmap);

drivers/scsi/scsi_lib_dma.c

···
+/*
+ * SCSI library functions depending on DMA
+ */
+
+#include <linux/blkdev.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_host.h>
+
+/**
+ * scsi_dma_map - perform DMA mapping against command's sg lists
+ * @cmd:	scsi command
+ *
+ * Returns the number of sg lists actually used, zero if the sg lists
+ * is NULL, or -ENOMEM if the mapping failed.
+ */
+int scsi_dma_map(struct scsi_cmnd *cmd)
+{
+	int nseg = 0;
+
+	if (scsi_sg_count(cmd)) {
+		struct device *dev = cmd->device->host->shost_gendev.parent;
+
+		nseg = dma_map_sg(dev, scsi_sglist(cmd), scsi_sg_count(cmd),
+				  cmd->sc_data_direction);
+		if (unlikely(!nseg))
+			return -ENOMEM;
+	}
+	return nseg;
+}
+EXPORT_SYMBOL(scsi_dma_map);
+
+/**
+ * scsi_dma_unmap - unmap command's sg lists mapped by scsi_dma_map
+ * @cmd:	scsi command
+ */
+void scsi_dma_unmap(struct scsi_cmnd *cmd)
+{
+	if (scsi_sg_count(cmd)) {
+		struct device *dev = cmd->device->host->shost_gendev.parent;
+
+		dma_unmap_sg(dev, scsi_sglist(cmd), scsi_sg_count(cmd),
+			     cmd->sc_data_direction);
+	}
+}
+EXPORT_SYMBOL(scsi_dma_unmap);