nuttx/mm/iob/Kconfig

#
# For a description of the syntax of this configuration file,
# see the file kconfig-language.txt in the NuttX tools repository.
#

menu "Common I/O Buffer Support"

config MM_IOB
	bool "Enable generic I/O buffer support"
	default n
	---help---
		This setting will build the common I/O buffer (IOB) support
		library.

if MM_IOB

config IOB_NBUFFERS
	int "Number of pre-allocated I/O buffers"
	default 36 if NET_WRITE_BUFFERS
	default 24 if !NET_WRITE_BUFFERS && NET_READAHEAD
	default 8 if !NET_WRITE_BUFFERS && !NET_READAHEAD
	---help---
		Each packet is represented by a series of small I/O buffers in a
		chain.  This setting determines the number of preallocated I/O
		buffers available for packet data.

config IOB_BUFSIZE
	int "Payload size of one I/O buffer"
	default 196
	---help---
		Each packet is represented by a series of small I/O buffers in a
		chain.  This setting determines the data payload each preallocated
		I/O buffer.

config IOB_ALIGNMENT
	int "Alignment size of each I/O buffer"
	default 4
	---help---
		The member io_data of all I/O buffers is aligned to the value
		specified by this configuration.

config IOB_SECTION
	string "The section where iob buffer is located"
	---help---
		The section where iob buffer is located.
		The section must be zero-initialized on system boot.

config IOB_NCHAINS
	int "Number of pre-allocated I/O buffer chain heads"
	default 0 if !NET_READAHEAD
	default IOB_NBUFFERS if NET_READAHEAD
	---help---
		These tiny nodes are used as "containers" to support queueing of
		I/O buffer chains.  This will limit the number of I/O transactions
		that can be "in-flight" at any give time.  The default value of
		zero disables this features.

		These generic I/O buffer chain containers are not currently used
		by any logic in NuttX.  That is because their other specialized
		I/O buffer chain containers that also carry a payload of usage
		specific information.

		Note: TCP doesn't use this.
		Note: UDP and CAN use this.

config IOB_THROTTLE
	int "I/O buffer throttle value"
	default 0 if !NET_WRITE_BUFFERS || !NET_READAHEAD
	default 8 if NET_WRITE_BUFFERS && NET_READAHEAD
	---help---
		TCP write buffering and read-ahead buffer use the same pool of free
		I/O buffers.  In order to prevent uncontrolled incoming TCP packets
		from hogging all of the available, pre-allocated I/O buffers, a
		throttling value is required.  This throttle value assures that
		I/O buffers will be denied to the read-ahead logic before TCP writes
		are halted.

config IOB_NOTIFIER
	bool "Support IOB notifications"
	default n
	depends on SCHED_WORKQUEUE
	select WQUEUE_NOTIFIER
	---help---
		Enable building of IOB notifier logic that will execute a worker
		function on the high priority work queue when an IOB is available.
		This is is a general purpose notifier, but was developed specifically to
		support poll() logic where the poll must wait for an IOB to become
		available.

config IOB_NOTIFIER_DIV
	int "Notification divider"
	default 4
	range 1 64
	depends on IOB_NOTIFIER
	---help---
		IOBs may become available at very high rates and the resulting
		notification processing can be substantial even if there is nothing
		waiting for a free IOB.  This divider will reduce that rate of
		notification.  This must be an even power of two.  Supported values
		include:  1, 2, 4, 8, 16, 32, 64.  The default value of 4 means that
		a notification will be sent only when there are a multiple of 4 IOBs
		available.

config IOB_DEBUG
	bool "Force I/O buffer debug"
	default n
	depends on DEBUG_FEATURES && !SYSLOG_BUFFER
	---help---
		This option will force debug output from I/O buffer logic.  This
		is not normally something that would want to do but is convenient
		if you are debugging the I/O buffer logic and do not want to get
		overloaded with other un-related debug output.

		NOTE that this selection is not available if IOBs are being used
		to syslog buffering logic (CONFIG_SYSLOG_BUFFER=y)!

endif # MM_IOB
endmenu # Common I/O buffer support