| /Documentation/devicetree/bindings/i2c/ |
| D | renesas,i2c.txt | 5 "renesas,i2c-r8a7743" if the device is a part of a R8A7743 SoC.
6 "renesas,i2c-r8a7744" if the device is a part of a R8A7744 SoC.
7 "renesas,i2c-r8a7745" if the device is a part of a R8A7745 SoC.
8 "renesas,i2c-r8a77470" if the device is a part of a R8A77470 SoC.
9 "renesas,i2c-r8a774a1" if the device is a part of a R8A774A1 SoC.
10 "renesas,i2c-r8a774c0" if the device is a part of a R8A774C0 SoC.
11 "renesas,i2c-r8a7778" if the device is a part of a R8A7778 SoC.
12 "renesas,i2c-r8a7779" if the device is a part of a R8A7779 SoC.
13 "renesas,i2c-r8a7790" if the device is a part of a R8A7790 SoC.
14 "renesas,i2c-r8a7791" if the device is a part of a R8A7791 SoC.
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| /Documentation/i2c/ |
| D | smbus-protocol.rst | 5 The following is a summary of the SMBus protocol. It applies to
11 which is a subset from the I2C protocol. Fortunately, many devices use
14 If you write a driver for some I2C device, please try to use the SMBus
21 Below is a list of SMBus protocol operations, and the functions executing
23 don't match these function names. For some of the operations which pass a
25 a different protocol operation entirely.
27 Each transaction type corresponds to a functionality flag. Before calling a
28 transaction function, a device driver should always check (just once) for
41 A, NA (1 bit) : Accept and reverse accept bit.
43 get a 10 bit I2C address.
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| D | i2c-protocol.rst | 14 A, NA (1 bit) : Accept and reverse accept bit.
16 get a 10 bit I2C address.
17 Comm (8 bits): Command byte, a data byte which often selects a register on
19 Data (8 bits): A plain data byte. Sometimes, I write DataLow, DataHigh
21 Count (8 bits): A data byte containing the length of a block operation.
33 S Addr Wr [A] Data [A] Data [A] ... [A] Data [A] P
41 S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P
49 They are just like the above transactions, but instead of a stop bit P
50 a start bit S is sent and the transaction continues. An example of
51 a byte read, followed by a byte write::
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| /Documentation/filesystems/nfs/ |
| D | exporting.rst | 9 All filesystem operations require a dentry (or two) as a starting
10 point. Local applications have a reference-counted hold on suitable
12 applications that access a filesystem via a remote filesystem protocol
13 such as NFS may not be able to hold such a reference, and so need a
14 different way to refer to a particular dentry. As the alternative
23 This byte string will be called a "filehandle fragment" as it
26 A filesystem which supports the mapping between filehandle fragments
34 The dcache normally contains a proper prefix of any given filesystem
38 maintained easily (by each object maintaining a reference count on
41 However when objects are included into the dcache by interpreting a
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| D | rpc-cache.txt | 1 This document gives a brief introduction to the caching
8 a wide variety of values to be caches.
10 There are a number of caches that are similar in structure though
11 quite possibly very different in content and use. There is a corpus
35 Creating a Cache
38 1/ A cache needs a datum to store. This is in the form of a
39 structure definition that must contain a
42 It will also contain a key and some content.
45 2/ A cache needs a "cache_detail" structure that
52 a pointer to the cache_detail embedded within the
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| /Documentation/filesystems/ |
| D | sharedsubtree.txt | 20 A process wants to clone its own namespace, but still wants to access the CD
33 a. shared mount
39 2a) A shared mount can be replicated to as many mountpoints and all the
44 Let's say /mnt has a mount that is shared.
56 a b c
59 a b c
61 Now let's say we mount a device at /tmp/a
62 # mount /dev/sd0 /tmp/a
64 #ls /tmp/a
67 #ls /mnt/a
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| D | mandatory-locking.txt | 11 The Linux implementation is prey to a number of difficult-to-fix race
14 - The write system call checks for a mandatory lock only once
15 at its start. It is therefore possible for a lock request to
17 A process may then see file data change even while a mandatory
19 - Similarly, an exclusive lock may be granted on a file after
20 the kernel has decided to proceed with a read, but before the
22 the file data in a state which should not have been visible
33 (and the lockf() library routine which is a wrapper around fcntl().) It is
34 normally a process' responsibility to check for locks on a file it wishes to
37 troublesome) is access to a user's mailbox. The mail user agent and the mail
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| /Documentation/maintainer/ |
| D | rebasing-and-merging.rst | 7 Maintaining a subsystem, as a general rule, requires a familiarity with the
8 Git source-code management system. Git is a powerful tool with a lot of
19 maintainers result from a desire to avoid merges, while others come from
20 merging a little too often.
25 "Rebasing" is the process of changing the history of a series of commits
26 within a repository. There are two different types of operations that are
30 - Changing the parent (starting) commit upon which a series of patches is
31 built. For example, a rebase operation could take a patch set built on
36 - Changing the history of a set of patches by fixing (or deleting) broken
42 Used properly, rebasing can yield a cleaner and clearer development
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| /Documentation/ABI/testing/ |
| D | sysfs-bus-rpmsg | 6 Every rpmsg device is a communication channel with a remote
7 processor. Channels are identified with a (textual) name,
18 Every rpmsg device is a communication channel with a remote
19 processor. Channels have a local ("source") rpmsg address,
21 starts listening on one end of a channel, it assigns it with
22 a unique rpmsg address (a 32 bits integer). This way when
24 dispatches them to the listening entity (a kernel driver).
36 Every rpmsg device is a communication channel with a remote
37 processor. Channels have a local ("source") rpmsg address,
39 starts listening on one end of a channel, it assigns it with
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| /Documentation/vm/ |
| D | frontswap.rst | 7 Frontswap provides a "transcendent memory" interface for swap pages.
9 swapped pages are saved in RAM (or a RAM-like device) instead of a swap disk.
14 See the LWN.net article `Transcendent memory in a nutshell`_
15 for a detailed overview of frontswap and related kernel parts)
17 .. _Transcendent memory in a nutshell: https://lwn.net/Articles/454795/
20 a "backing" store for a swap device. The storage is assumed to be
21 a synchronous concurrency-safe page-oriented "pseudo-RAM device" conforming
31 with the specified swap device number (aka "type"). A "store" will
33 offset associated with the page. A "load" will copy the page, if found,
40 Once a page is successfully stored, a matching load on the page will normally
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| /Documentation/driver-api/soundwire/ |
| D | error_handling.rst | 17 restarting from a known position. In the case of such errors outside of a
21 and after a number of such errors are detected the bus might be reset. Note
24 be distinguished, although a recurring bus clash when audio is enabled is a
25 indication of a bus allocation issue. The interrupt mechanism can also help
26 identify Slaves which detected a Bus Clash or a Parity Error, but they may
27 not be responsible for the errors so resetting them individually is not a
30 2. Command status: Each command is associated with a status, which only
33 current frame. A NAK indicates that the command was in error and will not
34 be applied. In case of a bad programming (command sent to non-existent
35 Slave or to a non-implemented register) or electrical issue, no response
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| /Documentation/process/ |
| D | 5.Posting.rst | 8 kernel. Unsurprisingly, the kernel development community has evolved a set
21 There is a constant temptation to avoid posting patches before they are
22 completely "ready." For simple patches, that is not a problem. If the
23 work being done is complex, though, there is a lot to be gained by getting
25 consider posting in-progress work, or even making a git tree available so
28 When posting code which is not yet considered ready for inclusion, it is a
38 There are a number of things which should be done before you consider
50 benchmarks showing what the impact (or benefit) of your change is; a
54 for an employer, the employer likely has a right to the work and must be
57 As a general rule, putting in some extra thought before posting code almost
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| /Documentation/ |
| D | kobject.txt | 13 place. Dealing with kobjects requires understanding a few different types,
15 easier, we'll take a multi-pass approach, starting with vague terms and
19 - A kobject is an object of type struct kobject. Kobjects have a name
20 and a reference count. A kobject also has a parent pointer (allowing
21 objects to be arranged into hierarchies), a specific type, and,
22 usually, a representation in the sysfs virtual filesystem.
32 - A ktype is the type of object that embeds a kobject. Every structure
33 that embeds a kobject needs a corresponding ktype. The ktype controls
36 - A kset is a group of kobjects. These kobjects can be of the same ktype
42 When you see a sysfs directory full of other directories, generally each
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| /Documentation/driver-api/dmaengine/ |
| D | provider.rst | 11 They have a given number of channels to use for the DMA transfers, and
12 a given number of requests lines.
21 will want to start a transfer, it will assert a DMA request (DRQ) by
24 A very simple DMA controller would only take into account a single
25 parameter: the transfer size. At each clock cycle, it would transfer a
30 require a specific number of bits to be transferred in a single
32 physical bus allows to maximize performances when doing a simple
33 memory copy operation, but our audio device could have a narrower FIFO
34 that requires data to be written exactly 16 or 24 bits at a time. This
35 is why most if not all of the DMA controllers can adjust this, using a
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| /Documentation/driver-api/ |
| D | generic-counter.rst | 10 Counter devices are prevalent within a diverse spectrum of industries.
11 The ubiquitous presence of these devices necessitates a common interface
14 drivers by introducing a generic counter interface for consumption. The
15 Generic Counter interface enables drivers to support and expose a common
23 counter devices consist of a core set of components. This core set of
27 There are three core components to a counter:
30 Count data for a set of Signals.
37 The association of a Signal with a respective Count.
41 A Count represents the count data for a set of Signals. The Generic
47 A Count has a count function mode which represents the update behavior
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| D | xillybus.rst | 37 An FPGA (Field Programmable Gate Array) is a piece of logic hardware, which
38 can be programmed to become virtually anything that is usually found as a
39 dedicated chipset: For instance, a display adapter, network interface card,
40 or even a processor with its peripherals. FPGAs are the LEGO of hardware:
43 available on the market as a chipset, so FPGAs are mostly used when some
47 The challenge with FPGAs is that everything is implemented at a very low
52 mathematical functions, a functional unit (e.g. a USB interface), an entire
53 processor (e.g. ARM) or anything that might come handy. Think of them as a
57 One of the daunting tasks in FPGA design is communicating with a fullblown
60 (registers, interrupts, DMA etc.) is a project in itself. When the FPGA's
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| /Documentation/locking/ |
| D | rt-mutex-design.rst | 24 Priority inversion is when a lower priority process executes while a higher
26 most of the time it can't be helped. Anytime a high priority process wants
27 to use a resource that a lower priority process has (a mutex for example),
29 with the resource. This is a priority inversion. What we want to prevent
31 priority process is prevented from running by a lower priority process for
35 processes, let's call them processes A, B, and C, where A is the highest
36 priority process, C is the lowest, and B is in between. A tries to grab a lock
38 meantime, B executes, and since B is of a higher priority than C, it preempts C,
39 but by doing so, it is in fact preempting A which is a higher priority process.
40 Now there's no way of knowing how long A will be sleeping waiting for C
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| /Documentation/networking/ |
| D | rxrpc.txt | 5 The RxRPC protocol driver provides a reliable two-phase transport on top of UDP
37 RxRPC is a two-layer protocol. There is a session layer which provides
39 layer, but implements a real network protocol; and there's the presentation
57 making the session part of it a Linux network protocol (AF_RXRPC).
59 (2) A two-phase protocol. The client transmits a blob (the request) and then
60 receives a blob (the reply), and the server receives the request and then
66 (4) A secure protocol, using the Linux kernel's key retention facility to
80 (2) provided with a protocol of the type of underlying transport they're going
102 (*) Each connection goes to a particular "service". A connection may not go
103 to multiple services. A service may be considered the RxRPC equivalent of
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| D | scaling.rst | 11 This document describes a set of complementary techniques in the Linux
28 (multi-queue). On reception, a NIC can send different packets to different
30 applying a filter to each packet that assigns it to one of a small number
31 of logical flows. Packets for each flow are steered to a separate receive
38 The filter used in RSS is typically a hash function over the network
39 and/or transport layer headers-- for example, a 4-tuple hash over
40 IP addresses and TCP ports of a packet. The most common hardware
41 implementation of RSS uses a 128-entry indirection table where each entry
42 stores a queue number. The receive queue for a packet is determined
44 packet (usually a Toeplitz hash), taking this number as a key into the
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| /Documentation/filesystems/configfs/ |
| D | configfs.txt | 14 configfs is a ram-based filesystem that provides the converse of
15 sysfs's functionality. Where sysfs is a filesystem-based view of
16 kernel objects, configfs is a filesystem-based manager of kernel
19 With sysfs, an object is created in kernel (for example, when a device
25 representation, and sysfs is merely a window on all this.
27 A configfs config_item is created via an explicit userspace operation:
36 system. One is not a replacement for the other.
40 configfs can be compiled as a module or into the kernel. You can access
47 subsystems. Once a client subsystem is loaded, it will appear as a
59 files, with a maximum size of one page (PAGE_SIZE, 4096 on i386). Preferably
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| /Documentation/admin-guide/cgroup-v1/ |
| D | cgroups.rst | 44 Control Groups provide a mechanism for aggregating/partitioning sets of
50 A *cgroup* associates a set of tasks with a set of parameters for one
53 A *subsystem* is a module that makes use of the task grouping
55 particular ways. A subsystem is typically a "resource controller" that
56 schedules a resource or applies per-cgroup limits, but it may be
57 anything that wants to act on a group of processes, e.g. a
60 A *hierarchy* is a set of cgroups arranged in a tree, such that
62 hierarchy, and a set of subsystems; each subsystem has system-specific
67 cgroups. Each hierarchy is a partition of all tasks in the system.
71 which cgroup a task is assigned, and list the task PIDs assigned to
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| D | devices.rst | 8 Implement a cgroup to track and enforce open and mknod restrictions
9 on device files. A device cgroup associates a device access
10 whitelist with each cgroup. A whitelist entry has 4 fields.
11 'type' is a (all), c (char), or b (block). 'all' means it applies
13 either an integer or * for all. Access is a composition of r
16 The root device cgroup starts with rwm to 'all'. A child device
17 cgroup gets a copy of the parent. Administrators can then remove
18 devices from the whitelist or add new entries. A child cgroup can
19 never receive a device access which is denied by its parent.
32 echo a > /sys/fs/cgroup/1/devices.deny
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| /Documentation/driver-api/driver-model/ |
| D | binding.rst | 5 Driver binding is the process of associating a device with a device
15 The bus type structure contains a list of all devices that are on that bus
16 type in the system. When device_register is called for a device, it is
17 inserted into the end of this list. The bus object also contains a
19 for a driver, it is inserted at the end of this list. These are the
26 When a new device is added, the bus's list of drivers is iterated over
30 Instead of trying to derive a complex state machine and matching
31 algorithm, it is up to the bus driver to provide a callback to compare
32 a device against the IDs of a driver. The bus returns 1 if a match was
37 If a match is found, the device's driver field is set to the driver
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| /Documentation/media/kapi/ |
| D | rc-core.rst | 12 Every time a key is pressed on a remote controller, a scan code is produced.
13 Also, on most hardware, keeping a key pressed for more than a few dozens of
14 milliseconds produce a repeat key event. That's somewhat similar to what
15 a normal keyboard or mouse is handled internally on Linux\ [#f1]_. So, the
22 produces one event for a key press and another one for key release. On
31 The infrared transmission is done by blinking a infrared emitter using a
36 In other words, a typical IR transmission can be viewed as a sequence of
37 *PULSE* and *SPACE* events, each with a given duration.
41 For example, the NEC protocol uses a carrier of 38kHz, and transmissions
42 start with a 9ms *PULSE* and a 4.5ms SPACE. It then transmits 16 bits of
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| /Documentation/powerpc/ |
| D | cxlflash.rst | 10 on Power 8 systems. CAPI can be thought of as a special tunneling
13 memory and generate page faults. As a result, the host interface to
19 devices as a PCI device by implementing a virtual PCI host bridge.
24 CXL provides a mechanism by which user space applications can
25 directly talk to a device (network or storage) bypassing the typical
26 kernel/device driver stack. The CXL Flash Adapter Driver enables a
29 The CXL Flash Adapter Driver is a kernel module that sits in the
30 SCSI stack as a low level device driver (below the SCSI disk and
40 - Any flash device (LUN) can be configured to be accessed as a
44 user space with a special block library. This mode further
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