Revision 5885b9b3f030f9b430f6b1c7fa396c885033f2f8 authored by Linus Torvalds on 16 December 2011, 19:14:42 UTC, committed by Linus Torvalds on 16 December 2011, 19:14:42 UTC
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound: ALSA: HDA: Use LPIB Position fix for Intel SCH Poulsbo ALSA: hda: fix mute led polarity for HP laptops with buggy BIOS ALSA: HDA: Set position fix to LPIB for an Atom/Poulsbo based device ASoC: Fix hx4700 error handling to free gpios if snd_soc_register_card fails ASoC: WM8958: correctly show firmware magic on mismatch ASoC: mxs: Add appropriate MODULE_ALIAS() ASoC: mxs: Add missing MODULE_LICENSE("GPL") ASoC: Fix WM8996 24.576MHz clock operation ASoC: Include linux/module.h for smdk2443_wm9710 ASoC: Fix a typo in jive_wm8750 ASoC: Fix build dependency for SND_SOC_JZ4740_CODEC ASoC: Include linux/io.h for jz4740 codec
netif-msg.txt
________________
NETIF Msg Level
The design of the network interface message level setting.
History
The design of the debugging message interface was guided and
constrained by backwards compatibility previous practice. It is useful
to understand the history and evolution in order to understand current
practice and relate it to older driver source code.
From the beginning of Linux, each network device driver has had a local
integer variable that controls the debug message level. The message
level ranged from 0 to 7, and monotonically increased in verbosity.
The message level was not precisely defined past level 3, but were
always implemented within +-1 of the specified level. Drivers tended
to shed the more verbose level messages as they matured.
0 Minimal messages, only essential information on fatal errors.
1 Standard messages, initialization status. No run-time messages
2 Special media selection messages, generally timer-driver.
3 Interface starts and stops, including normal status messages
4 Tx and Rx frame error messages, and abnormal driver operation
5 Tx packet queue information, interrupt events.
6 Status on each completed Tx packet and received Rx packets
7 Initial contents of Tx and Rx packets
Initially this message level variable was uniquely named in each driver
e.g. "lance_debug", so that a kernel symbolic debugger could locate and
modify the setting. When kernel modules became common, the variables
were consistently renamed to "debug" and allowed to be set as a module
parameter.
This approach worked well. However there is always a demand for
additional features. Over the years the following emerged as
reasonable and easily implemented enhancements
Using an ioctl() call to modify the level.
Per-interface rather than per-driver message level setting.
More selective control over the type of messages emitted.
The netif_msg recommendation adds these features with only a minor
complexity and code size increase.
The recommendation is the following points
Retaining the per-driver integer variable "debug" as a module
parameter with a default level of '1'.
Adding a per-interface private variable named "msg_enable". The
variable is a bit map rather than a level, and is initialized as
1 << debug
Or more precisely
debug < 0 ? 0 : 1 << min(sizeof(int)-1, debug)
Messages should changes from
if (debug > 1)
printk(MSG_DEBUG "%s: ...
to
if (np->msg_enable & NETIF_MSG_LINK)
printk(MSG_DEBUG "%s: ...
The set of message levels is named
Old level Name Bit position
0 NETIF_MSG_DRV 0x0001
1 NETIF_MSG_PROBE 0x0002
2 NETIF_MSG_LINK 0x0004
2 NETIF_MSG_TIMER 0x0004
3 NETIF_MSG_IFDOWN 0x0008
3 NETIF_MSG_IFUP 0x0008
4 NETIF_MSG_RX_ERR 0x0010
4 NETIF_MSG_TX_ERR 0x0010
5 NETIF_MSG_TX_QUEUED 0x0020
5 NETIF_MSG_INTR 0x0020
6 NETIF_MSG_TX_DONE 0x0040
6 NETIF_MSG_RX_STATUS 0x0040
7 NETIF_MSG_PKTDATA 0x0080
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