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+What: /sys/class/ata_*
+Description:
+ Provide a place in sysfs for storing the ATA topology of the
+ system. This allows retrieving various information about ATA
+ objects.
+
+Files under /sys/class/ata_port
+-------------------------------
+
+For each port, a directory ataX is created where X is the ata_port_id of the
+port. The device parent is the ata host device.
+
+
+What: /sys/class/ata_port/ataX/nr_pmp_links
+What: /sys/class/ata_port/ataX/idle_irq
+Date: May, 2010
+KernelVersion: v2.6.37
+Contact: Gwendal Grignou <gwendal@chromium.org>
+Description:
+ nr_pmp_links: (RO) If a SATA Port Multiplier (PM) is
+ connected, the number of links behind it.
+
+ idle_irq: (RO) Number of IRQ received by the port while
+ idle [some ata HBA only].
+
+
+What: /sys/class/ata_port/ataX/port_no
+Date: May, 2013
+KernelVersion: v3.11
+Contact: Gwendal Grignou <gwendal@chromium.org>
+Description:
+ (RO) Host local port number. While registering host controller,
+ port numbers are tracked based upon number of ports available on
+ the controller. This attribute is needed by udev for composing
+ persistent links in /dev/disk/by-path.
+
+Files under /sys/class/ata_link
+-------------------------------
+
+Behind each port, there is a ata_link. If there is a SATA PM in the topology, 15
+ata_link objects are created.
+
+If a link is behind a port, the directory name is linkX, where X is ata_port_id
+of the port. If a link is behind a PM, its name is linkX.Y where X is
+ata_port_id of the parent port and Y the PM port.
+
+
+What: /sys/class/ata_link/linkX[.Y]/hw_sata_spd_limit
+What: /sys/class/ata_link/linkX[.Y]/sata_spd_limit
+What: /sys/class/ata_link/linkX[.Y]/sata_spd
+Date: May, 2010
+KernelVersion: v2.6.37
+Contact: Gwendal Grignou <gwendal@chromium.org>
+Description:
+ hw_sata_spd_limit: (RO) Maximum speed supported by the
+ connected SATA device.
+
+ sata_spd_limit: (RO) Maximum speed imposed by libata.
+
+ sata_spd: (RO) Current speed of the link
+ eg. 1.5, 3 Gbps etc.
+
+
+Files under /sys/class/ata_device
+---------------------------------
+
+Behind each link, up to two ata devices are created.
+The name of the directory is devX[.Y].Z where:
+- X is ata_port_id of the port where the device is connected,
+- Y the port of the PM if any, and
+- Z the device id: for PATA, there is usually 2 devices [0,1], only 1 for SATA.
+
+
+What: /sys/class/ata_device/devX[.Y].Z/spdn_cnt
+What: /sys/class/ata_device/devX[.Y].Z/gscr
+What: /sys/class/ata_device/devX[.Y].Z/ering
+What: /sys/class/ata_device/devX[.Y].Z/id
+What: /sys/class/ata_device/devX[.Y].Z/pio_mode
+What: /sys/class/ata_device/devX[.Y].Z/xfer_mode
+What: /sys/class/ata_device/devX[.Y].Z/dma_mode
+What: /sys/class/ata_device/devX[.Y].Z/class
+Date: May, 2010
+KernelVersion: v2.6.37
+Contact: Gwendal Grignou <gwendal@chromium.org>
+Description:
+ spdn_cnt: (RO) Number of times libata decided to lower the
+ speed of link due to errors.
+
+ gscr: (RO) Cached result of the dump of PM GSCR
+ register. Valid registers are:
+
+ 0: SATA_PMP_GSCR_PROD_ID,
+ 1: SATA_PMP_GSCR_REV,
+ 2: SATA_PMP_GSCR_PORT_INFO,
+ 32: SATA_PMP_GSCR_ERROR,
+ 33: SATA_PMP_GSCR_ERROR_EN,
+ 64: SATA_PMP_GSCR_FEAT,
+ 96: SATA_PMP_GSCR_FEAT_EN,
+ 130: SATA_PMP_GSCR_SII_GPIO
+
+ Only valid if the device is a PM.
+
+ ering: (RO) Formatted output of the error ring of the
+ device.
+
+ id: (RO) Cached result of IDENTIFY command, as
+ described in ATA8 7.16 and 7.17. Only valid if
+ the device is not a PM.
+
+ pio_mode: (RO) PIO transfer mode used by the device.
+ Mostly used by PATA devices.
+
+ xfer_mode: (RO) Current transfer mode. Mostly used by
+ PATA devices.
+
+ dma_mode: (RO) DMA transfer mode used by the device.
+ Mostly used by PATA devices.
+
+ class: (RO) Device class. Can be "ata" for disk,
+ "atapi" for packet device, "pmp" for PM, or
+ "none" if no device was found behind the link.
+
+
+What: /sys/class/ata_device/devX[.Y].Z/trim
+Date: May, 2015
+KernelVersion: v4.10
+Contact: Gwendal Grignou <gwendal@chromium.org>
+Description:
+ (RO) Shows the DSM TRIM mode currently used by the device. Valid
+ values are:
+
+ unsupported: Drive does not support DSM TRIM
+
+ unqueued: Drive supports unqueued DSM TRIM only
+
+ queued: Drive supports queued DSM TRIM
+
+ forced_unqueued: Drive's queued DSM support is known to
+ be buggy and only unqueued TRIM commands
+ are sent