^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) .. SPDX-License-Identifier: GPL-2.0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) ===============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) NETIF Msg Level
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) ===============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) The design of the network interface message level setting.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) History
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) -------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) The design of the debugging message interface was guided and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) constrained by backwards compatibility previous practice. It is useful
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) to understand the history and evolution in order to understand current
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) practice and relate it to older driver source code.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) From the beginning of Linux, each network device driver has had a local
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) integer variable that controls the debug message level. The message
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) level ranged from 0 to 7, and monotonically increased in verbosity.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) The message level was not precisely defined past level 3, but were
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) always implemented within +-1 of the specified level. Drivers tended
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) to shed the more verbose level messages as they matured.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) - 0 Minimal messages, only essential information on fatal errors.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) - 1 Standard messages, initialization status. No run-time messages
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) - 2 Special media selection messages, generally timer-driver.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) - 3 Interface starts and stops, including normal status messages
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) - 4 Tx and Rx frame error messages, and abnormal driver operation
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) - 5 Tx packet queue information, interrupt events.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) - 6 Status on each completed Tx packet and received Rx packets
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) - 7 Initial contents of Tx and Rx packets
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) Initially this message level variable was uniquely named in each driver
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) e.g. "lance_debug", so that a kernel symbolic debugger could locate and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) modify the setting. When kernel modules became common, the variables
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) were consistently renamed to "debug" and allowed to be set as a module
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) parameter.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) This approach worked well. However there is always a demand for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) additional features. Over the years the following emerged as
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) reasonable and easily implemented enhancements
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) - Using an ioctl() call to modify the level.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) - Per-interface rather than per-driver message level setting.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) - More selective control over the type of messages emitted.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) The netif_msg recommendation adds these features with only a minor
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) complexity and code size increase.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) The recommendation is the following points
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) - Retaining the per-driver integer variable "debug" as a module
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) parameter with a default level of '1'.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) - Adding a per-interface private variable named "msg_enable". The
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) variable is a bit map rather than a level, and is initialized as::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) 1 << debug
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) Or more precisely::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) debug < 0 ? 0 : 1 << min(sizeof(int)-1, debug)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) Messages should changes from::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) if (debug > 1)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) printk(MSG_DEBUG "%s: ...
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) to::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) if (np->msg_enable & NETIF_MSG_LINK)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) printk(MSG_DEBUG "%s: ...
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76) The set of message levels is named
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) ========= =================== ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80) Old level Name Bit position
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81) ========= =================== ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) 0 NETIF_MSG_DRV 0x0001
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) 1 NETIF_MSG_PROBE 0x0002
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) 2 NETIF_MSG_LINK 0x0004
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) 2 NETIF_MSG_TIMER 0x0004
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) 3 NETIF_MSG_IFDOWN 0x0008
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) 3 NETIF_MSG_IFUP 0x0008
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) 4 NETIF_MSG_RX_ERR 0x0010
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) 4 NETIF_MSG_TX_ERR 0x0010
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) 5 NETIF_MSG_TX_QUEUED 0x0020
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) 5 NETIF_MSG_INTR 0x0020
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92) 6 NETIF_MSG_TX_DONE 0x0040
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) 6 NETIF_MSG_RX_STATUS 0x0040
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94) 7 NETIF_MSG_PKTDATA 0x0080
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) ========= =================== ============
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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