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>

1 files changed, 46 insertions, 0 deletions

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");