| /Documentation/userspace-api/media/v4l/ |
| D | func-read.rst | 4 .. _func-read:
7 V4L2 read()
13 v4l2-read - Read from a V4L2 device
22 .. c:function:: ssize_t read( int fd, void *buf, size_t count )
34 Max number of bytes to read
39 :c:func:`read()` attempts to read up to ``count`` bytes from file
42 section, see ##. If ``count`` is zero, :c:func:`read()` returns zero
45 :c:func:`read()` call will provide at most one frame (two fields)
48 By default :c:func:`read()` blocks until data becomes available. When
54 :c:func:`read()` function must also support :c:func:`select()` and
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| /Documentation/ABI/testing/ |
| D | sysfs-bus-coresight-devices-tmc | 14 Description: (Read) Defines the size, in 32-bit words, of the local RAM buffer.
15 The value is read directly from HW register RSZ, 0x004.
21 Description: (Read) Shows the value held by the TMC status register. The value
22 is read directly from HW register STS, 0x00C.
28 Description: (Read) Shows the value held by the TMC RAM Read Pointer register
29 that is used to read entries from the Trace RAM over the APB
30 interface. The value is read directly from HW register RRP,
37 Description: (Read) Shows the value held by the TMC RAM Write Pointer register
39 the CoreSight bus into the Trace RAM. The value is read directly
46 Description: (Read) Similar to "trigger_cntr" above except that this value is
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| D | sysfs-bus-coresight-devices-etb10 | 26 Description: (Read) Defines the depth, in words, of the trace RAM in powers of
27 2. The value is read directly from HW register RDP, 0x004.
33 Description: (Read) Shows the value held by the ETB status register. The value
34 is read directly from HW register STS, 0x00C.
40 Description: (Read) Shows the value held by the ETB RAM Read Pointer register
41 that is used to read entries from the Trace RAM over the APB
42 interface. The value is read directly from HW register RRP,
49 Description: (Read) Shows the value held by the ETB RAM Write Pointer register
51 the CoreSight bus into the Trace RAM. The value is read directly
58 Description: (Read) Similar to "trigger_cntr" above except that this value is
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| D | sysfs-platform-dfl-fme | 5 Description: Read-only. One DFL FPGA device may have more than 1
7 number of ports on the FPGA device when read it.
13 Description: Read-only. It returns Bitstream (static FPGA region)
21 Description: Read-only. It returns Bitstream (static FPGA region) meta
29 Description: Read-only. It returns cache size of this FPGA device.
35 Description: Read-only. It returns fabric version of this FPGA device.
43 Description: Read-only. It returns socket_id to indicate which socket
52 Description: Read-Write. Read this file for errors detected on pcie0 link.
61 Description: Read-Write. Read this file for errors detected on pcie1 link.
70 Description: Read-only. It returns non-fatal errors detected.
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| D | sysfs-platform-dfl-port | 5 Description: Read-only. It returns id of this port. One DFL FPGA device
13 Description: Read-only. User can program different PR bitstreams to FPGA
22 Description: Read-only. It reports the APx (AFU Power) state, different APx
30 Description: Read-write. Read this file for AP1 (AFU Power State 1) event.
38 Description: Read-write. Read this file for AP2 (AFU Power State 2) event.
46 Description: Read-write. Read or set AFU latency tolerance reporting value.
61 Description: Read-only. Read this file to get the status of issued command
75 Description: Read-only. Read this file to get the status of issued command
82 Description: Read-Write. Read this file to get errors detected on port and
93 Description: Read-only. Read this file to get the first error detected by
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| D | configfs-spear-pcie-gadget | 20 link used to enable ltssm and read its status.
21 int_type used to configure and read type of supported interrupt
23 to read no of MSI granted.
26 vendor_id used to write and read vendor id (hex)
27 device_id used to write and read device id (hex)
28 bar0_size used to write and read bar0_size
29 bar0_address used to write and read bar0 mapped area in hex.
30 bar0_rw_offset used to write and read offset of bar0 where bar0_data
31 will be written or read.
32 bar0_data used to write and read data at bar0_rw_offset.
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| D | sysfs-bus-coresight-devices-cti | 11 Description: (Read) Indicate if the CTI hardware is powered.
17 Description: (Read) Display the associated CTM ID
23 Description: (Read) Number of devices connected to triggers on this CTI
29 Description: (Read) Name of connected device <N>
35 Description: (Read) Input trigger signals from connected device <N>
41 Description: (Read) Functional types for the input trigger signals
48 Description: (Read) Output trigger signals to connected device <N>
54 Description: (Read) Functional types for the output trigger signals
67 Description: (RW) Read or write the CTIINEN register selected by inout_sel.
73 Description: (RW) Read or write the CTIOUTEN register selected by inout_sel.
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| D | sysfs-class-watchdog | 5 It is a read only file. It contains status of the watchdog
13 It is a read only file. It contains options of watchdog device.
19 It is a read only file. It contains firmware version of
26 It is a read only file. It contains identity string of
33 It is a read/write file. While reading, it gives '1'
45 It is a read only file. It gives active/inactive status of
52 It is a read only file. It contains watchdog device's
60 It is a read only file. It contains value of time left for
68 It is a read only file. It is read to know about current
75 It is a read only file. It specifies the time in seconds before
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| D | sysfs-driver-xdata | 17 The user can read the current PCIe link throughput generated
24 The file is read and write.
26 What: /sys/class/misc/dw-xdata-pcie.<device>/read
31 will create read TLPs frames - from the Endpoint to the Root
38 echo 1 > /sys/class/misc/dw-xdata-pcie.<device>/read
40 echo 0 > /sys/class/misc/dw-xdata-pcie.<device>/read
42 The user can read the current PCIe link throughput generated
46 cat /sys/class/misc/dw-xdata-pcie.<device>/read
49 The file is read and write.
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| D | sysfs-driver-w1_therm | 5 (RW) read or write TH and TL (Temperature High an Low) alarms.
55 values after power-on. Read or write are :
63 actual resolution is read back from the chip and verified. Error
75 * If a bulk read has been triggered, it will directly
76 return the temperature computed when the bulk read
80 * If no bulk read has been triggered, it will trigger
95 *read*: return 2 lines with the hexa output data sent on the
115 (RW) trigger a bulk read conversion. read the status
117 *read*:
122 value has not been read yet
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| D | debugfs-scmi-raw | 9 Any subsequently received response can be read from this same
12 and sent while the replies are read back one message at time
24 Any subsequently received response can be read from this same
26 Any additional delayed response received afterwards can be read
30 and sent while the replies are read back one message at time
40 can be read from this entry.
41 Each read gives back one message at time (receiving an EOF at
51 read from this entry.
52 Each read gives back one message at time (receiving an EOF at
62 still pending to be read out for instance <n>, to be immediately
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| D | sysfs-driver-ufs | 23 The file is read only.
33 The file is read only.
43 The file is read only.
54 The file is read only.
64 The file is read only.
75 The file is read only.
86 The file is read only.
93 descriptor could be read after partial initialization phase
98 The file is read only.
109 The file is read only.
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| /Documentation/filesystems/spufs/ |
| D | spufs.rst | 44 tem calls like read(2) or write(2), but often support only a subset of
49 All files that support the read(2) operation also support readv(2) and
57 possible operations, e.g. read access on the wbox file.
68 read(2), pread(2), write(2), pwrite(2), lseek(2)
81 The first SPU to CPU communication mailbox. This file is read-only and
82 can be read in units of 32 bits. The file can only be used in non-
86 read(2)
87 If a count smaller than four is requested, read returns -1 and
90 When data has been read successfully, four bytes are placed in
96 the first mailbox file, but can be read in blocking I/O mode, and the
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| /Documentation/ABI/stable/ |
| D | sysfs-bus-nvmem | 6 This read/write attribute allows users to set read-write
7 devices as read-only and back to read-write from userspace.
11 Read returns '0' or '1' for read-write or read-only modes
23 This file allows user to read/write the raw NVMEM contents.
46 This read-only attribute allows user to read the NVMEM
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| /Documentation/admin-guide/ |
| D | ufs.rst | 20 default value, supported as read-only
24 supported as read-write
28 supported as read-write
35 supported as read-write
39 supported as read-write
43 supported as read-only
47 supported as read-only
51 supported as read-only
55 supported as read-only
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| /Documentation/userspace-api/media/rc/ |
| D | lirc-read.rst | 4 .. _lirc-read:
7 LIRC read()
13 lirc-read - Read from a LIRC device
22 .. c:function:: ssize_t read( int fd, void *buf, size_t count )
34 Max number of bytes to read
39 :c:func:`read()` attempts to read up to ``count`` bytes from file
41 :c:func:`read()` returns zero and has no other results. If ``count``
50 read from the chardev.
62 On success, the number of bytes read is returned. It is not an error if
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| /Documentation/filesystems/ |
| D | netfs_library.rst | 12 - Buffered read helpers.
13 - Read helper functions.
14 - Read helper structures.
15 - Read helper operations.
16 - Read helper procedure.
17 - Read helper cache API.
25 just includes turning various VM buffered read operations into requests to read
95 Buffered Read Helpers
98 The library provides a set of read helpers that handle the ->read_folio(),
114 * Allow the netfs to partially fulfil a read, which will then be resubmitted.
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| /Documentation/wmi/devices/ |
| D | msi-wmi-platform.rst | 26 [WmiDataId(1), read, write, Description("16 bytes of data")] uint8 Bytes[16];
33 [WmiDataId(1), read, write, Description("32 bytes of data")] uint8 Bytes[32];
40 [key, read] string InstanceName;
41 [read] boolean Active;
43 [WmiMethodId(1), Implemented, read, write, Description("Return the contents of a package")]
46 [WmiMethodId(2), Implemented, read, write, Description("Set the contents of a package")]
49 [WmiMethodId(3), Implemented, read, write, Description("Return the contents of a package")]
52 [WmiMethodId(4), Implemented, read, write, Description("Set the contents of a package")]
55 [WmiMethodId(5), Implemented, read, write, Description("Return the contents of a package")]
58 [WmiMethodId(6), Implemented, read, write, Description("Set the contents of a package")]
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| /Documentation/userspace-api/gpio/ |
| D | gpio-lineinfo-changed-read.rst | 11 gpio-v2-lineinfo-changed-read.rst.
16 GPIO_LINEINFO_CHANGED_READ - Read line info change events for watched lines
22 ``int read(int chip_fd, void *buf, size_t count)``
40 Read line info change events for watched lines from the chip.
47 not its value. Use gpio-lineevent-data-read.rst to receive events when a
55 from where they can be read by userspace at its convenience using `read()`.
59 The buffer may overflow if bursts of events occur quicker than they are read
63 Events read from the buffer are always in the same order that they were
68 userspace, `read()` supports copying multiple events. The number of events
72 A `read()` will block if no event is available and the ``chip_fd`` has not
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| D | gpio-v2-lineinfo-changed-read.rst | 12 GPIO_V2_LINEINFO_CHANGED_READ - Read line info changed events for watched
18 ``int read(int chip_fd, void *buf, size_t count)``
36 Read line info changed events for watched lines from the chip.
43 not its value. Use gpio-v2-line-event-read.rst to receive events when a
51 from where they can be read by userspace at its convenience using `read()`.
55 The buffer may overflow if bursts of events occur quicker than they are read
59 Events read from the buffer are always in the same order that they were
64 userspace, `read()` supports copying multiple events. The number of events
68 A `read()` will block if no event is available and the ``chip_fd`` has not
77 On success the number of bytes read, which will be a multiple of the size
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| D | gpio-lineevent-data-read.rst | 11 gpio-v2-line-event-read.rst.
16 GPIO_LINEEVENT_DATA_READ - Read edge detection events from a line event.
21 ``int read(int event_fd, void *buf, size_t count)``
40 Read edge detection events for a line from a line event.
53 occurrence and stores them in a buffer from where they can be read by
54 userspace at its convenience using `read()`.
62 Events read from the buffer are always in the same order that they were
67 The buffer may overflow if bursts of events occur quicker than they are read
72 userspace, `read()` supports copying multiple events. The number of events
76 The `read()` will block if no event is available and the ``event_fd`` has not
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| D | gpio-v2-line-event-read.rst | 12 GPIO_V2_LINE_EVENT_READ - Read edge detection events for lines from a request.
17 ``int read(int req_fd, void *buf, size_t count)``
36 Read edge detection events for lines from a request.
49 occurrence and stores them in a buffer from where they can be read by
50 userspace at its convenience using `read()`.
52 Events read from the buffer are always in the same order that they were
61 The buffer may overflow if bursts of events occur quicker than they are read
67 userspace, `read()` supports copying multiple events. The number of events
75 The `read()` will block if no event is available and the ``req_fd`` has not
84 On success the number of bytes read, which will be a multiple of the size of a
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| /Documentation/hwmon/ |
| D | ltc2992.rst | 29 The following attributes are supported. Limits are read-write,
30 all other attributes are read-only.
39 inX_min_alarm An undervoltage occurred. Cleared on read.
40 inX_max_alarm An overvoltage occurred. Cleared on read.
47 currX_min_alarm An undercurrent occurred. Cleared on read.
48 currX_max_alarm An overcurrent occurred. Cleared on read.
55 powerX_min_alarm An underpower occurred. Cleared on read.
56 powerX_max_alarm An overpower occurred. Cleared on read.
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| /Documentation/locking/ |
| D | seqlock.rst | 9 lockless readers (read-only retry loops), and no writer starvation. They
15 read side critical section is even and the same sequence count value is
16 read again at the end of the critical section. The data in the set must
17 be copied out inside the read side critical section. If the sequence
28 or interrupted by read side sections. Otherwise the reader will spin for
48 write side section. If the read section can be invoked from hardirq or
80 Read path::
85 /* ... [[read-side critical section]] ... */
118 The sequence counter read and write APIs can take either a plain
139 Read path: same as in :ref:`seqcount_t`.
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| /Documentation/arch/s390/ |
| D | monreader.rst | 2 Linux API for read access to z/VM Monitor Records
15 usable from user space and allows read access to the z/VM Monitor Records
129 The following file operations are supported: open, release, read, poll.
130 There are two alternative methods for reading: either non-blocking read in
131 conjunction with polling, or blocking read without polling. IOCTLs are not
134 Read:
154 <0 byte read>
160 <0 byte read>
165 read with a return value of 0 (0 byte read).
167 read successfully, including the closing 0 byte read. Therefore you should
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