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>