[PATCH 1/4] 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 |   17 +++++++++++++++++
 1 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/include/linux/ata.h b/include/linux/ata.h
index 80364b6..d9a94bd 100644
--- a/include/linux/ata.h
+++ b/include/linux/ata.h
@@ -707,6 +707,23 @@ static inline int ata_id_has_dword_io(const u16 *id)
 	return 0;
 }
 
+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 (ata_id_major_version(id) >= 7
+	    && (((id[ATA_ID_CFSSE] & 0xC000) == 0x4000
+		 && id[ATA_ID_CFSSE] & (1 << 13))
+		|| ((id[ATA_ID_CSF_DEFAULT] & 0xC000) == 0x4000
+		    && (id[ATA_ID_CSF_DEFAULT] & (1 << 13)))))
+		return 1;
+	return 0;
+}
+
 static inline int ata_id_current_chs_valid(const u16 *id)
 {
 	/* For ATA-1 devices, if the INITIALIZE DEVICE PARAMETERS command