[Qemu-block] [PATCH 01/16] ahci: Rename NCQFIS structure fields

[John Snow]

Several fields of the NCQFIS structure are ambiguously named. This patch
clarifies the intended (if unsupported) usage of the NCQ fields to aid
in creating more meaningful debug messages through the NCQ codepaths.

Signed-off-by: John Snow <address@hidden>
---
 hw/ide/ahci.h | 35 +++++++++++++++++++++++++----------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/hw/ide/ahci.h b/hw/ide/ahci.h
index 501c002..6d167f2 100644
--- a/hw/ide/ahci.h
+++ b/hw/ide/ahci.h
@@ -195,6 +195,9 @@
 #define RECEIVE_FPDMA_QUEUED               0x65
 #define SEND_FPDMA_QUEUED                  0x64
 
+#define NCQ_FIS_FUA_MASK                   0x80
+#define NCQ_FIS_RARC_MASK                  0x01
+
 #define RES_FIS_DSFIS                      0x00
 #define RES_FIS_PSFIS                      0x20
 #define RES_FIS_RFIS                       0x40
@@ -312,27 +315,39 @@ extern const VMStateDescription vmstate_ahci;
     .offset     = vmstate_offset_value(_state, _field, AHCIState),   \
 }
 
+/**
+ * NCQFrame is the same as a Register H2D FIS (described in SATA 3.2),
+ * but some fields have been re-mapped and re-purposed, as seen in
+ * SATA 3.2 section 13.6.4.1 ("READ FPDMA QUEUED")
+ *
+ * cmd_fis[3], feature 7:0, becomes sector count 7:0.
+ * cmd_fis[7], device 7:0, uses bit 7 as the Force Unit Access bit.
+ * cmd_fis[11], feature 15:8, becomes sector count 15:8.
+ * cmd_fis[12], count 7:0, becomes the NCQ TAG (7:3) and RARC bit (0)
+ * cmd_fis[13], count 15:8, becomes the priority value (7:6)
+ * bytes 16-19 become an le32 "auxiliary" field.
+ */
 typedef struct NCQFrame {
     uint8_t fis_type;
     uint8_t c;
     uint8_t command;
-    uint8_t sector_count_low;
+    uint8_t sector_count_low;  /* (feature 7:0) */
     uint8_t lba0;
     uint8_t lba1;
     uint8_t lba2;
-    uint8_t fua;
+    uint8_t fua;               /* (device 7:0) */
     uint8_t lba3;
     uint8_t lba4;
     uint8_t lba5;
-    uint8_t sector_count_high;
-    uint8_t tag;
-    uint8_t reserved5;
-    uint8_t reserved6;
+    uint8_t sector_count_high; /* (feature 15:8) */
+    uint8_t tag;               /* (count 0:7) */
+    uint8_t prio;              /* (count 15:8) */
+    uint8_t icc;
     uint8_t control;
-    uint8_t reserved7;
-    uint8_t reserved8;
-    uint8_t reserved9;
-    uint8_t reserved10;
+    uint8_t aux0;
+    uint8_t aux1;
+    uint8_t aux2;
+    uint8_t aux3;
 } QEMU_PACKED NCQFrame;
 
 typedef struct SDBFIS {
-- 
2.1.0