incubator-nuttx/libc/misc/Kconfig

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

config LIBC_IOCTL_VARIADIC
	bool "Enable variadic ioctl()"
	default n
	---help---
		By default, NuttX implements the "old style," three-parameter,
		ioctl() interface with this function prototype:

			int ioctl(int fd, int req, unsigned long arg);

		That function is implemented as part of the VFS.  If
		LIBC_IOCTL_VARIADIC is selected, then an additional compatibility
		layer will be provided in the C library.  The enabled, then function
		prototype will become:

			int ioctl(int fd, int req, ...);

		The ioctl() is not controlled by any standard so it is really
		arbitrary which format you used.  You may select the variadic
		function prototype with this option.  That will slightly increase
		code size and ioctl() processing time.  It will not support a
		variable number of arguments and it still always expects to see a
		third argument of type 'unsigned long'.  The only benefit of this
		alternative function signature is that it may provide greater
		compatibility if you are porting code from other platforms that use
		the variadic ioctl() function.

		WARNING:  Use of this option could cause subtle system errors is
		the third argument is omitted or if the sizeof the thread argument
		is anything other than sizeof (unsigned long).  Most small integers
		will be promoted to 'int'.  The following assertion appears in ioctl():

			DEBUGASSERT(sizeof(int)        == sizeof(unsigned long) &&
			            sizeof(FAR void *) == sizeof(unsigned long));

		Do not enable this option if the above is not true.  32-bit ARM
		should pass this test with all three types having sizeof(type) == 4
		bytes.  'float' should also be tested.  But 'long long' and 'double'
		are out of the question!  Don't event try to pass them.

		And what will happen if no third argument is passed?  In most cases,
		this should just result in a garbage value for arg.  But you may
		discover cases where something worse happens!

config LIB_SENDFILE_BUFSIZE
	int "sendfile() buffer size"
	default 512
	---help---
		Size of the I/O buffer to allocate in sendfile().  Default: 512b

comment "Non-standard Library Support"

config LIB_CRC64_FAST
	bool "Fast CRC64"
	default n
	---help---
		Enable the CRC64 lookup table to compute the CRC64 faster.

config LIB_KBDCODEC
	bool "Keyboard CODEC"
	default n
	---help---
		In NuttX, a keyboard/keypad driver is simply a character driver that
		may have an (optional) encoding/decoding layer on the data returned
		by the character driver. A keyboard may return simple text data
		(alphabetic, numeric, and punctuaction) or control characters
		(enter, control-C, etc.).  However, in addition, most keyboards
		support actions that cannot be represented as text data. Such
		actions include things like cursor controls (home, up arrow,
		page down, etc.), editing functions (insert, delete, etc.), volume
		controls, (mute, volume up, etc.) and other special functions.
		Some special encoding may be required to multiplex these two classes
		of data.

		This option enables the functions that implement the encoding and
		decoding of keyboard data.  These are the interfaces prototyped in
		include/nuttx/input/kbd_codec.h.  While not correctly a part of
		the C library, it is included here because the decoding side of this
		interface must be accessible by end user programs.

config LIB_SLCDCODEC
	bool "Segment LCD CODEC"
	default n
	---help---
		In NuttX, a character-oriented, segment LCD (SLCD) driver is simply
		a character device that may have an (optional) encoding/decoding
		layer on the data provided to the SLCD driver.  The application may
		provide simple text data (alphabetic, numeric, and punctuaction) or
		control characters (enter, control-C, etc.).  However, in addition,
		most SLCDs support actions that cannot be represented as text data.
		Such actions include things like cursor controls (home, up arrow,
		page down, etc.) and other special functions (e.g., blinking).  Some
		special encoding may be required to multiplex these two classes of
		data.

		This option enables the functions that implement the encoding and
		decoding of SLCD data.  These are the interfaces prototyped in
		include/nuttx/lcd/slcd_codec.h.  While not correctly a part of the C
		library, it is included here because the encoding side of this
		interface must be accessible by end user programs.