[PATCH 2/5] Introduce ata_id_has_unload()

[Elias Oltmanns <eo@nebensachen.de>]

Add a function to check an ATA device's id for head unload support as
specified in ATA-7.

Signed-off-by: Elias Oltmanns <eo@nebensachen.de>
---

 include/linux/ata.h |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/include/linux/ata.h b/include/linux/ata.h
index cf4ef6d..c92ac10 100644
--- a/include/linux/ata.h
+++ b/include/linux/ata.h
@@ -530,6 +530,21 @@ static inline bool ata_id_has_dipm(const u16 *id)
 }
 
 
+static inline int ata_id_has_unload(const u16 *id)
+{
+	/*
+	 * ATA-7 specifies two places to indicate unload feature support.
+	 * Since I don't really understand the difference, I'll just check
+	 * both and only return zero if none of them indicates otherwise.
+	 */
+	if ((id[ATA_ID_CFSSE] & 0xC000) == 0x4000
+	    && id[ATA_ID_CFSSE] & (1 << 13))
+		return id[ATA_ID_CFSSE] & (1 << 13);
+	if ((id[ATA_ID_CSF_DEFAULT] & 0xC000) == 0x4000)
+		return id[ATA_ID_CSF_DEFAULT] & (1 << 13);
+	return 0;
+}
+
 static inline int ata_id_has_fua(const u16 *id)
 {
 	if ((id[ATA_ID_CFSSE] & 0xC000) != 0x4000)