ide: add ide-4drives host driver (take 3)

CONFIG_BLK_DEV_4DRIVES deserves its own host driver:

* Add drivers/ide/legacy/ide-4drives.c and move "4drives" support there.

* Add ide-4drives.o in the link order after all other legacy host
  drivers enabled by "ide0=" options (they all are mutually exclusive).

* Make ide-4drives host driver probe itself for IDE devices instead of
  indirectly depending on ide_generic host driver.

* Add "probe" module parameter to ide-4drives and update documentation.

v2:
* s/paramater/parameter/ in ide.txt. (Noticed by Randy Dunlap)

v3:
* s/ide_4drives.probe/ide-4drives.probe/ in help entry.
  (Noticed by Sergei Shtylyov)

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

4 files changed, 52 insertions, 14 deletions

diff --git a/drivers/ide/Kconfig b/drivers/ide/Kconfig
index 29dd99caaf50..ec6b4a80e333 100644
--- a/drivers/ide/Kconfig
+++ b/drivers/ide/Kconfig
@@ -1035,8 +1035,8 @@ config BLK_DEV_4DRIVES
           Certain older chipsets, including the Tekram 690CD, use a single set
           of I/O ports at 0x1f0 to control up to four drives, instead of the
           customary two drives per port. Support for this can be enabled at
-          runtime using the "ide0=four" kernel boot parameter if you say Y
-          here.
+          runtime using the "ide-4drives.probe" kernel boot parameter if you
+          say Y here.
 
 config BLK_DEV_ALI14XX
         tristate "ALI M14xx support"
diff --git a/drivers/ide/ide.c b/drivers/ide/ide.c
index adecf45a0849..690b5ff4d88f 100644
--- a/drivers/ide/ide.c
+++ b/drivers/ide/ide.c
@@ -976,6 +976,7 @@ extern int probe_dtc2278;
 extern int probe_ht6560b;
 extern int probe_qd65xx;
 extern int cmd640_vlb;
+extern int probe_4drives;
 
 static int __initdata is_chipset_set;
 
@@ -1187,19 +1188,9 @@ static int __init ide_setup(char *s)
 #endif
 #ifdef CONFIG_BLK_DEV_4DRIVES
                         case -11: /* "four" drives on one set of ports */
-                        {
-                                ide_hwif_t *mate = &ide_hwifs[hw^1];
-                                mate->drives[0].select.all ^= 0x20;
-                                mate->drives[1].select.all ^= 0x20;
-                                hwif->chipset = mate->chipset = ide_4drives;
-                                mate->irq = hwif->irq;
-                                memcpy(mate->io_ports, hwif->io_ports, sizeof(hwif->io_ports));
-                                hwif->mate = mate;
-                                mate->mate = hwif;
-                                hwif->serialized = mate->serialized = 1;
+                                probe_4drives = 1;
                                 goto obsolete_option;
-                        }
-#endif /* CONFIG_BLK_DEV_4DRIVES */
+#endif
                         case -10: /* minus10 */
                         case -9: /* minus9 */
                         case -8: /* minus8 */
diff --git a/drivers/ide/legacy/Makefile b/drivers/ide/legacy/Makefile
index 7043ec7d1e05..6939329f89e8 100644
--- a/drivers/ide/legacy/Makefile
+++ b/drivers/ide/legacy/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_BLK_DEV_UMC8672)		+= umc8672.o
 obj-$(CONFIG_BLK_DEV_DTC2278)           += dtc2278.o
 obj-$(CONFIG_BLK_DEV_HT6560B)           += ht6560b.o
 obj-$(CONFIG_BLK_DEV_QD65XX)            += qd65xx.o
+obj-$(CONFIG_BLK_DEV_4DRIVES)           += ide-4drives.o
 
 obj-$(CONFIG_BLK_DEV_GAYLE)             += gayle.o
 obj-$(CONFIG_BLK_DEV_FALCON_IDE)        += falconide.o
diff --git a/drivers/ide/legacy/ide-4drives.c b/drivers/ide/legacy/ide-4drives.c
new file mode 100644
index 000000000000..5aa7e93cfd31
--- /dev/null
+++ b/drivers/ide/legacy/ide-4drives.c
@@ -0,0 +1,46 @@
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/ide.h>
+
+int probe_4drives = 0;
+
+module_param_named(probe, probe_4drives, bool, 0);
+MODULE_PARM_DESC(probe, "probe for generic IDE chipset with 4 drives/port");
+
+static int __init ide_4drives_init(void)
+{
+        ide_hwif_t *hwif, *mate;
+        u8 idx[4] = { 0, 1, 0xff, 0xff };
+
+        if (probe_4drives == 0)
+                return -ENODEV;
+
+        hwif = &ide_hwifs[0];
+        mate = &ide_hwifs[1];
+
+        memcpy(mate->io_ports, hwif->io_ports, sizeof(hwif->io_ports));
+
+        mate->irq = hwif->irq;
+
+        mate->chipset = hwif->chipset = ide_4drives;
+
+        mate->drives[0].select.all ^= 0x20;
+        mate->drives[1].select.all ^= 0x20;
+
+        hwif->mate = mate;
+        mate->mate = hwif;
+
+        hwif->serialized = mate->serialized = 1;
+
+        ide_device_add(idx, NULL);
+
+        return 0;
+}
+
+module_init(ide_4drives_init);
+
+MODULE_AUTHOR("Bartlomiej Zolnierkiewicz");
+MODULE_DESCRIPTION("generic IDE chipset with 4 drives/port support");
+MODULE_LICENSE("GPL");