[PATCH v2] ata: libata-transport: fix {dma|pio|xfer}_mode sysfs files

[Sergey Shtylyov <s.shtylyov@omp.ru>]

The {dma|pio}_mode sysfs files are incorrectly documented as having a list
of the supported DMA/PIO transfer modes, while the corresponding fields of
the *struct* ata_device hold the transfer mode IDs, not masks.

To match these docs, the {dma|pio}_mode (and even xfer_mode!) sysfs files
are handled by the ata_bitfield_name_match() macro which leads to reading
such kind of nonsense from them:

$ cat /sys/class/ata_device/dev3.0/pio_mode
XFER_UDMA_7, XFER_UDMA_6, XFER_UDMA_5, XFER_UDMA_4, XFER_MW_DMA_4,
XFER_PIO_6, XFER_PIO_5, XFER_PIO_4, XFER_PIO_3, XFER_PIO_2, XFER_PIO_1,
XFER_PIO_0

Using the correct ata_bitfield_name_search() macro fixes that:

$ cat /sys/class/ata_device/dev3.0/pio_mode
XFER_PIO_4

While fixing the file misdocumentation, somewhat reword the {dma|pio}_mode
file doc and add a note about being mostly useful for the PATA devices to
the xfer_mode file doc...

Fixes: d9027470b886 ("[libata] Add ATA transport class")
Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Cc: stable@vger.kernel.org

---
This patch is against the 'master' branch of Damien's 'libata.git' repo.

Changes in version 2:
- added the Documentation/ABI/testing/sysfs-ata file, updating the patch
  description accordingly.

 Documentation/ABI/testing/sysfs-ata |   11 ++++++-----
 drivers/ata/libata-transport.c      |    2 +-
 2 files changed, 7 insertions(+), 6 deletions(-)

Index: libata/Documentation/ABI/testing/sysfs-ata
===================================================================
--- libata.orig/Documentation/ABI/testing/sysfs-ata
+++ libata/Documentation/ABI/testing/sysfs-ata
@@ -107,13 +107,14 @@ Description:
 				described in ATA8 7.16 and 7.17. Only valid if
 				the device is not a PM.
 
-		pio_mode:	(RO) Transfer modes supported by the device when
-				in PIO mode. Mostly used by PATA device.
+		pio_mode:	(RO) PIO transfer mode used by the device.
+				Mostly used by the PATA devices.
 
-		xfer_mode:	(RO) Current transfer mode
+		xfer_mode:	(RO) Current transfer mode. Mostly used by
+				the PATA devices.
 
-		dma_mode:	(RO) Transfer modes supported by the device when
-				in DMA mode. Mostly used by PATA device.
+		dma_mode:	(RO) DMA transfer mode used by the device.
+				Mostly used by the PATA devices.
 
 		class:		(RO) Device class. Can be "ata" for disk,
 				"atapi" for packet device, "pmp" for PM, or
Index: libata/drivers/ata/libata-transport.c
===================================================================
--- libata.orig/drivers/ata/libata-transport.c
+++ libata/drivers/ata/libata-transport.c
@@ -196,7 +196,7 @@ static struct {
 	{ XFER_PIO_0,			"XFER_PIO_0" },
 	{ XFER_PIO_SLOW,		"XFER_PIO_SLOW" }
 };
-ata_bitfield_name_match(xfer,ata_xfer_names)
+ata_bitfield_name_search(xfer, ata_xfer_names)
 
 /*
  * ATA Port attributes