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authorLinus Torvalds <torvalds@linux-foundation.org>2026-08-19 10:09:22 -0700
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Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-mediagrafted
Pull media updates from Mauro Carvalho Chehab: - v4l2-core: added ISP statistics support and per-block validation - v4l2-core: Allow unknown HDR10 white point and luminance - New camera sensors: Sony IMX678 and IMX471m, Himax HM1092 IR sensor - New codec: Milos: VPU v2.0 codec support - isp driver: gained support for Dreamchip RPPX1 ISP framework - vsp1 driver: gained support for RZ/T2H and RZ/N2H - Novalake driver: gained CVS support for new NVL hardware - dvb-core: fix feed leak on failed DMX_ADD_PID - several driver fixes, cleanups and minor improvements * tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (308 commits) media: ipu-bridge: check all DMI entries when overriding sensor rotation media: v4l2-async: avoid deleting unlinked ASC entry on link error media: rzg2l-cru: Align bytesperline to hardware DMA stride requirement media: intel/ipu6: fix async notifier cleanup leak on parse error media: staging/ipu7: fix async notifier UAF on probe error path media: amd: isp4: fix self-deadlock in isp4sd_pwron_and_init() error path media: amd: isp4: release partial allocations in isp4if_alloc_fw_gpumem() media: rcar-isp: Fix VSPX reference leaks media: rcar-isp: Release ISPCORE resources media: i2c: imx415: Release runtime PM reference on VBLANK error media: i2c: imx415: Return test pattern write errors media: renesas: vsp1: Declare index variables in for loop statement media: renesas: vsp1: Make reset control optional to support platforms without a reset line media: dt-bindings: media: renesas,vsp1: Document RZ/T2H and RZ/N2H SoCs media: dt-bindings: media: renesas,fcp: Document RZ/T2H and RZ/N2H SoCs media: nxp: imx8-isi: Add additional 32-bit RGB format support media: nxp: imx8-isi: Add 16-bit raw Bayer format support media: nxp: imx8-isi: Implement per-stream reference counting for multiplexed streams media: nxp: imx8-isi: Use BIT_ULL() for 64-bit stream masks media: nxp: imx8-isi: Correct color map between V4L2 and ISI ...
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+=====================
+SCSI Interfaces Guide
+=====================
+
+:Author: James Bottomley
+:Author: Rob Landley
+
+Introduction
+============
+
+Protocol vs bus
+---------------
+
+Once upon a time, the Small Computer Systems Interface defined both a
+parallel I/O bus and a data protocol to connect a wide variety of
+peripherals (disk drives, tape drives, modems, printers, scanners,
+optical drives, test equipment, and medical devices) to a host computer.
+
+Although the old parallel (fast/wide/ultra) SCSI bus has largely fallen
+out of use, the SCSI command set is more widely used than ever to
+communicate with devices over a number of different buses.
+
+The `SCSI protocol <https://www.t10.org/scsi-3.htm>`__ is a big-endian
+peer-to-peer packet based protocol. SCSI commands are 6, 10, 12, or 16
+bytes long, often followed by an associated data payload.
+
+SCSI commands can be transported over just about any kind of bus, and
+are the default protocol for storage devices attached to USB, SATA, SAS,
+Fibre Channel, FireWire, and ATAPI devices. SCSI packets are also
+commonly exchanged over Infiniband,
+TCP/IP (`iSCSI <https://en.wikipedia.org/wiki/ISCSI>`__), even `Parallel
+ports <http://cyberelk.net/tim/parport/parscsi.html>`__.
+
+Design of the Linux SCSI subsystem
+----------------------------------
+
+The SCSI subsystem uses a three layer design, with upper, mid, and low
+layers. Every operation involving the SCSI subsystem (such as reading a
+sector from a disk) uses one driver at each of the 3 levels: one upper
+layer driver, one lower layer driver, and the SCSI midlayer.
+
+The SCSI upper layer provides the interface between userspace and the
+kernel, in the form of block and char device nodes for I/O and ioctl().
+The SCSI lower layer contains drivers for specific hardware devices.
+
+In between is the SCSI mid-layer, analogous to a network routing layer
+such as the IPv4 stack. The SCSI mid-layer routes a packet based data
+protocol between the upper layer's /dev nodes and the corresponding
+devices in the lower layer. It manages command queues, provides error
+handling and power management functions, and responds to ioctl()
+requests.
+
+SCSI upper layer
+================
+
+The upper layer supports the user-kernel interface by providing device
+nodes.
+
+sd (SCSI Disk)
+--------------
+
+sd (sd_mod.o)
+
+sr (SCSI CD-ROM)
+----------------
+
+sr (sr_mod.o)
+
+st (SCSI Tape)
+--------------
+
+st (st.o)
+
+sg (SCSI Generic)
+-----------------
+
+sg (sg.o)
+
+ch (SCSI Media Changer)
+-----------------------
+
+ch (ch.c)
+
+SCSI mid layer
+==============
+
+SCSI midlayer implementation
+----------------------------
+
+include/scsi/scsi_device.h
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. kernel-doc:: include/scsi/scsi_device.h
+ :internal:
+
+drivers/scsi/scsi.c
+~~~~~~~~~~~~~~~~~~~
+
+Main file for the SCSI midlayer.
+
+.. kernel-doc:: drivers/scsi/scsi.c
+ :export:
+
+drivers/scsi/scsicam.c
+~~~~~~~~~~~~~~~~~~~~~~
+
+`SCSI Common Access
+Method <http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf>`__ support
+functions, for use with HDIO_GETGEO, etc.
+
+.. kernel-doc:: drivers/scsi/scsicam.c
+ :export:
+
+drivers/scsi/scsi_error.c
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Common SCSI error/timeout handling routines.
+
+.. kernel-doc:: drivers/scsi/scsi_error.c
+ :export:
+
+drivers/scsi/scsi_devinfo.c
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Manage scsi_dev_info_list, which tracks blacklisted and whitelisted
+devices.
+
+.. kernel-doc:: drivers/scsi/scsi_devinfo.c
+ :export:
+
+drivers/scsi/scsi_ioctl.c
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Handle ioctl() calls for SCSI devices.
+
+.. kernel-doc:: drivers/scsi/scsi_ioctl.c
+ :export:
+
+drivers/scsi/scsi_lib.c
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+SCSI queuing library.
+
+.. kernel-doc:: drivers/scsi/scsi_lib.c
+ :export:
+
+drivers/scsi/scsi_lib_dma.c
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+SCSI library functions depending on DMA (map and unmap scatter-gather
+lists).
+
+.. kernel-doc:: drivers/scsi/scsi_lib_dma.c
+ :export:
+
+drivers/scsi/scsi_proc.c
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The functions in this file provide an interface between the PROC file
+system and the SCSI device drivers It is mainly used for debugging,
+statistics and to pass information directly to the lowlevel driver. I.E.
+plumbing to manage /proc/scsi/\*
+
+.. kernel-doc:: drivers/scsi/scsi_proc.c
+
+drivers/scsi/scsi_netlink.c
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Infrastructure to provide async events from transports to userspace via
+netlink, using a single NETLINK_SCSITRANSPORT protocol for all
+transports. See `the original patch submission
+<https://lore.kernel.org/linux-scsi/1155070439.6275.5.camel@localhost.localdomain/>`__
+for more details.
+
+.. kernel-doc:: drivers/scsi/scsi_netlink.c
+ :internal:
+
+drivers/scsi/scsi_scan.c
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Scan a host to determine which (if any) devices are attached. The
+general scanning/probing algorithm is as follows, exceptions are made to
+it depending on device specific flags, compilation options, and global
+variable (boot or module load time) settings. A specific LUN is scanned
+via an INQUIRY command; if the LUN has a device attached, a scsi_device
+is allocated and setup for it. For every id of every channel on the
+given host, start by scanning LUN 0. Skip hosts that don't respond at
+all to a scan of LUN 0. Otherwise, if LUN 0 has a device attached,
+allocate and setup a scsi_device for it. If target is SCSI-3 or up,
+issue a REPORT LUN, and scan all of the LUNs returned by the REPORT LUN;
+else, sequentially scan LUNs up until some maximum is reached, or a LUN
+is seen that cannot have a device attached to it.
+
+.. kernel-doc:: drivers/scsi/scsi_scan.c
+ :export:
+
+drivers/scsi/scsi_sysctl.c
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Set up the sysctl entry: "/dev/scsi/logging_level"
+(DEV_SCSI_LOGGING_LEVEL) which sets/returns scsi_logging_level.
+
+drivers/scsi/scsi_sysfs.c
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+SCSI sysfs interface routines.
+
+.. kernel-doc:: drivers/scsi/scsi_sysfs.c
+ :export:
+
+drivers/scsi/hosts.c
+~~~~~~~~~~~~~~~~~~~~
+
+mid to lowlevel SCSI driver interface
+
+.. kernel-doc:: drivers/scsi/hosts.c
+ :export:
+
+drivers/scsi/scsi_common.c
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+general support functions
+
+.. kernel-doc:: drivers/scsi/scsi_common.c
+ :export:
+
+Transport classes
+-----------------
+
+Transport classes are service libraries for drivers in the SCSI lower
+layer, which expose transport attributes in sysfs.
+
+Fibre Channel transport
+~~~~~~~~~~~~~~~~~~~~~~~
+
+The file drivers/scsi/scsi_transport_fc.c defines transport attributes
+for Fibre Channel.
+
+.. kernel-doc:: drivers/scsi/scsi_transport_fc.c
+ :export:
+
+iSCSI transport class
+~~~~~~~~~~~~~~~~~~~~~
+
+The file drivers/scsi/scsi_transport_iscsi.c defines transport
+attributes for the iSCSI class, which sends SCSI packets over TCP/IP
+connections.
+
+.. kernel-doc:: drivers/scsi/scsi_transport_iscsi.c
+ :export:
+
+Serial Attached SCSI (SAS) transport class
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The file drivers/scsi/scsi_transport_sas.c defines transport
+attributes for Serial Attached SCSI, a variant of SATA aimed at large
+high-end systems.
+
+The SAS transport class contains common code to deal with SAS HBAs, an
+approximated representation of SAS topologies in the driver model, and
+various sysfs attributes to expose these topologies and management
+interfaces to userspace.
+
+In addition to the basic SCSI core objects this transport class
+introduces two additional intermediate objects: The SAS PHY as
+represented by struct sas_phy defines an "outgoing" PHY on a SAS HBA or
+Expander, and the SAS remote PHY represented by struct sas_rphy defines
+an "incoming" PHY on a SAS Expander or end device. Note that this is
+purely a software concept, the underlying hardware for a PHY and a
+remote PHY is the exactly the same.
+
+There is no concept of a SAS port in this code, users can see what PHYs
+form a wide port based on the port_identifier attribute, which is the
+same for all PHYs in a port.
+
+.. kernel-doc:: drivers/scsi/scsi_transport_sas.c
+ :export:
+
+SATA transport class
+~~~~~~~~~~~~~~~~~~~~
+
+The SATA transport is handled by libata, which has its own book of
+documentation in this directory.
+
+Parallel SCSI (SPI) transport class
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The file drivers/scsi/scsi_transport_spi.c defines transport
+attributes for traditional (fast/wide/ultra) SCSI buses.
+
+.. kernel-doc:: drivers/scsi/scsi_transport_spi.c
+ :export:
+
+SCSI RDMA (SRP) transport class
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The file drivers/scsi/scsi_transport_srp.c defines transport
+attributes for SCSI over Remote Direct Memory Access.
+
+.. kernel-doc:: drivers/scsi/scsi_transport_srp.c
+ :export:
+
+SCSI lower layer
+================
+
+Host Bus Adapter transport types
+--------------------------------
+
+Many modern device controllers use the SCSI command set as a protocol to
+communicate with their devices through many different types of physical
+connections.
+
+In SCSI language a bus capable of carrying SCSI commands is called a
+"transport", and a controller connecting to such a bus is called a "host
+bus adapter" (HBA).
+
+Debug transport
+~~~~~~~~~~~~~~~
+
+The file drivers/scsi/scsi_debug.c simulates a host adapter with a
+variable number of disks (or disk like devices) attached, sharing a
+common amount of RAM. Does a lot of checking to make sure that we are
+not getting blocks mixed up, and panics the kernel if anything out of
+the ordinary is seen.
+
+To be more realistic, the simulated devices have the transport
+attributes of SAS disks.
+
+For documentation see http://sg.danny.cz/sg/scsi_debug.html
+
+todo
+~~~~
+
+Parallel (fast/wide/ultra) SCSI, USB, SATA, SAS, Fibre Channel,
+FireWire, ATAPI devices, Infiniband, Parallel ports,
+netlink...