SD(3)                                                       SD(3)

     NAME
          sd - storage device interface

     SYNOPSIS
          bind #S /dev

          /dev/sdctl
          /dev/sdCu/ctl
          /dev/sdCu/raw
          /dev/sdCu/data
          ...

     DESCRIPTION
          The storage device interface serves a two-level directory
          giving access to multiple storage units, typically ATA(PI)
          or SCSI discs.  Each unit is accessed via files in the
          directory named by the controller to which it is attached,
          C, and by its unit number u. The controller naming conven-
          tion for ATA(PI) units starts with the first controller
          being named `C', the second `D', etc. up to a maximum of 4
          controllers ([C-F]); legacy controllers are always 'C' and
          'D'.  There can be a maximum of 2 units per ATA(PI) con-
          troller ([01]).  The controller naming convention for SCSI
          units starts with the first controller being named `0', the
          second `1', etc. up to a maximum of 16 controllers
          ([0-9a-f]).  There can be a maximum of 16 units per SCSI
          controller ([0-9a-f]).

          Units are not accessed before the first attach.  Units may
          be individually attached using the attach specifier, for
          example

               bind -a '#SsdD0' /dev

          An attach without a specifier will cause the driver to scan
          for all possible units before processing the rest of the
          name.

          The subdirectory for each unit contains two files, ctl and
          raw. In addition, if the unit is a direct-access disc of
          some type it may be split into partitions and the subdirec-
          tory may contain a file per partition.  By default, the par-
          tition data will exist for such media.

          Partitions are added and deleted by writing to the ctl file

               part name start-sector end-sector
               delpart name

          The default data partition may be deleted.  A partition

     SD(3)                                                       SD(3)

          cannot be deleted if a process has it open.  If a change of
          removable media is detected, the new media cannot be opened
          until all open partitions on the old media are closed.

          Partitions are usually created using fdisk and prep(8); the
          convention is to name non-Plan 9 partitions after their cor-
          responding operating systems (e.g., /dev/sdC0/dos) and Plan
          9 partitions according to their function (e.g.,
          /dev/sdC0/swap).  The example in prep(8) shows how this is
          done.

          Reading the ctl file returns at least one line of textual
          information about the unit.  The first line will always be
          prefixed by inquiry and will give a manufacturer and model
          number if possible.  A line prefixed by config will be
          returned for appropriate media, e.g. for ATA(PI) units the
          remainder of the line contains configuration information
          from the device's identify command (config and capabilities)
          and also the available I/O transfer options; this is a diag-
          nostic aid.  A line prefixed by geometry will be returned
          for appropriate media; at least two numbers will follow, the
          first being the number of sectors contained in the unit and
          the second the sector size in bytes.  Any remaining informa-
          tion on the geometry line is unit-dependent, for instance,
          head, cylinder and sector counts for ATA discs.  If any par-
          titions are defined for the media, their name, start-sector
          and end-sector will be returned, prefixed by part.

               % cat /dev/sdD0/ctl
               inquiry KENWOOD CD-ROM UCR-421  208E10/20/99  7.39  2 M0
               config 85C0 capabilities 0F00 dma 00550004 dmactl 00000000
               geometry 242725 2352
               part data 0 242725
               %

          The use of DMA and multi-sector read/write commands may be
          enabled and disabled on ATA(PI) units by writing to the ctl
          file dma and rwm respectively followed by on or off.  For
          example, to enable DMA on a unit that supports it:

               % echo 'dma on'>/dev/sd00/ctl

          If supported by the unit, the standby timer may be enabled:

               % echo 'standby T'>/dev/sdC0/ctl

          where T is the standby timer period in seconds.  T must be
          between 30 and 1200, or can be 0 to disable the timer.

          The raw file is used to execute an arbitrary command on the
          unit at a low level.  This is used by programs such as
          scuzz(8) to manipulate devices that do not fit the simple

     SD(3)                                                       SD(3)

          storage model or for maintenance purposes.  The following
          steps may be taken to execute a command

          -  Write the command to the raw file;

          -  Read or write data associated with the command, according
             to the direction of the transfer.

          -  Read the raw file to retrieve the status of the command,
             returned as a text integer.

          Reading /dev/sdctl yields information about each controller,
          one line per controller.  Writing `config message' to
          /dev/sdctl passes message to the legacy configuration
          machinery, used to set attributes such as IRQ, port and
          size.  Writing `ctltype message' to /dev/sdctl passes
          message to ctltype's wtopctl function with a nil sdev argu-
          ment, where ctltype is a known controller type such as ata
          or scsi.  Writing `sdctlletter message' to /dev/sdctl passes
          message to sdctlletter's wtopctl function with an sdev argu-
          ment corresponding to the named controller, where ctlletter
          is a known controller letter such as C or 0.

     SOURCE
          /sys/src/9/port/devsd.c
          /sys/src/9/*/sd*.[hc]

     SEE ALSO
          scuzz(8)

     BUGS
          LUNs (logical unit numbers) are not implemented.  For (S)ATA
          drives, LUNs are not merely ignored but are actively pre-
          vented from working except for INQUIRY commands.

          The 4 controller limit for ATA(PI) is not enforced.

          No account is taken of some buggy ATA PCI controllers such
          as the CMD640.

          ATA(PI) units come up with DMA and multi-sector read/write
          capability disabled.