libata: allow LLDs w/o any reset method

Some old SFF controllers don't have any way to reset the channel.
Currently, this isn't supported and libata EH causes an oops.  Allow
LLDs w/o any reset method and just assume ATA class in such cases.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index 698ce2cea52c..681252fd8143 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -2150,6 +2150,15 @@ int ata_eh_reset(struct ata_link *link, int classify,
                         ap->ops->set_piomode(ap, dev);
         }
 
+        if (!softreset && !hardreset) {
+                if (verbose)
+                        ata_link_printk(link, KERN_INFO, "no reset method "
+                                        "available, skipping reset\n");
+                if (!(lflags & ATA_LFLAG_ASSUME_CLASS))
+                        lflags |= ATA_LFLAG_ASSUME_ATA;
+                goto done;
+        }
+
         /* Determine which reset to use and record in ehc->i.action.
          * prereset() may examine and modify it.
          */
@@ -2254,6 +2263,7 @@ int ata_eh_reset(struct ata_link *link, int classify,
                 lflags |= ATA_LFLAG_ASSUME_ATA;
         }
 
+ done:
         ata_link_for_each_dev(dev, link) {
                 /* After the reset, the device state is PIO 0 and the
                  * controller state is undefined.  Reset also wakes up