修改led为gpio

hc

2024-10-12 a5969cabbb4660eab42b6ef0412cbbd1200cf14d

 kernel/Documentation/ABI/testing/dev-kmsg
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@@ -6,13 +6,14 @@
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 		to the kernel's printk buffer.
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 		Injecting messages:
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+
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 		Every write() to the opened device node places a log entry in
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 		the kernel's printk buffer.
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 		The logged line can be prefixed with a <N> syslog prefix, which
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 		carries the syslog priority and facility. The single decimal
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 		prefix number is composed of the 3 lowest bits being the syslog
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-		priority and the higher bits the syslog facility number.
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+		priority and the next 8 bits the syslog facility number.
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 		If no prefix is given, the priority number is the default kernel
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 		log priority and the facility number is set to LOG_USER (1). It
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@@ -21,6 +22,7 @@
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 		the messages can always be reliably determined.
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 		Accessing the buffer:
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+
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 		Every read() from the opened device node receives one record
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 		of the kernel's printk buffer.
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@@ -48,6 +50,7 @@
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 		if needed, without limiting the interface to a single reader.
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 		The device supports seek with the following parameters:
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+
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 		SEEK_SET, 0
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 		  seek to the first entry in the buffer
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 		SEEK_END, 0
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@@ -55,6 +58,17 @@
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 		SEEK_DATA, 0
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 		  seek after the last record available at the time
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 		  the last SYSLOG_ACTION_CLEAR was issued.
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+
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+		Other seek operations or offsets are not supported because of
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+		the special behavior this device has. The device allows to read
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+		or write only whole variable length messages (records) that are
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+		stored in a ring buffer.
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+
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+		Because of the non-standard behavior also the error values are
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+		non-standard. -ESPIPE is returned for non-zero offset. -EINVAL
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+		is returned for other operations, e.g. SEEK_CUR. This behavior
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+		and values are historical and could not be modified without the
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+		risk of breaking userspace.
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 		The output format consists of a prefix carrying the syslog
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 		prefix including priority and facility, the 64 bit message
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@@ -76,27 +90,30 @@
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 		readable context of the message, for reliable processing in
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 		userspace.
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-		Example:
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-		7,160,424069,-;pci_root PNP0A03:00: host bridge window [io  0x0000-0x0cf7] (ignored)
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-		 SUBSYSTEM=acpi
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-		 DEVICE=+acpi:PNP0A03:00
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-		6,339,5140900,-;NET: Registered protocol family 10
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-		30,340,5690716,-;udevd[80]: starting version 181
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+		Example::
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+
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+		  7,160,424069,-;pci_root PNP0A03:00: host bridge window [io  0x0000-0x0cf7] (ignored)
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+		   SUBSYSTEM=acpi
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+		   DEVICE=+acpi:PNP0A03:00
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+		  6,339,5140900,-;NET: Registered protocol family 10
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+		  30,340,5690716,-;udevd[80]: starting version 181
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 		The DEVICE= key uniquely identifies devices the following way:
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-		  b12:8        - block dev_t
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-		  c127:3       - char dev_t
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-		  n8           - netdev ifindex
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-		  +sound:card0 - subsystem:devname
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+
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+		  ============  =================
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+		  b12:8         block dev_t
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+		  c127:3        char dev_t
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+		  n8            netdev ifindex
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+		  +sound:card0  subsystem:devname
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+		  ============  =================
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 		The flags field carries '-' by default. A 'c' indicates a
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-		fragment of a line. All following fragments are flagged with
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-		'+'. Note, that these hints about continuation lines are not
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-		necessarily correct, and the stream could be interleaved with
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-		unrelated messages, but merging the lines in the output
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-		usually produces better human readable results. A similar
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-		logic is used internally when messages are printed to the
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-		console, /proc/kmsg or the syslog() syscall.
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+		fragment of a line. Note, that these hints about continuation
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+		lines are not necessarily correct, and the stream could be
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+		interleaved with unrelated messages, but merging the lines in
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+		the output usually produces better human readable results. A
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+		similar logic is used internally when messages are printed to
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+		the console, /proc/kmsg or the syslog() syscall.
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 		By default, kernel tries to avoid fragments by concatenating
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 		when it can and fragments are rare; however, when extended