libata: add command name parsing for error output

This patch improve libata's output for error/notification messages
to allow easier comprehension and debugging:

When ATAPI commands issued through the SCSI layer fail, use SCSI
functions to print the CDB in human-readable form instead of just
dumping out the CDB in hex.

Print out the name of the failed command (as defined by the ATA
specification) in error handling output along with the raw register
contents.

When reporting status of ACPI taskfile commands executed on resume,
also output the names of the commands being executed (or not) in
readable form.

Since the extra data for printing command names increases kernel
size slightly, a config option has been added to allow disabling
command name output (as well as some of the error register parsing)
for those highly sensitive to kernel text size.

Signed-off-by: Robert Hancock <hancockrwd@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/ata/libata.h b/drivers/ata/libata.h
index 89a1e00..be8e262 100644
--- a/drivers/ata/libata.h
+++ b/drivers/ata/libata.h
@@ -164,6 +164,7 @@
 extern void ata_eh_done(struct ata_link *link, struct ata_device *dev,
 			unsigned int action);
 extern void ata_eh_autopsy(struct ata_port *ap);
+const char *ata_get_cmd_descript(u8 command);
 extern void ata_eh_report(struct ata_port *ap);
 extern int ata_eh_reset(struct ata_link *link, int classify,
 			ata_prereset_fn_t prereset, ata_reset_fn_t softreset,