Config service "cfg:u"

Command Header	Available since system version	Description
0x00010082		GetConfigInfoBlk2
0x00020000		SecureInfoGetRegion
0x00030040		GenHashConsoleUnique/GetTransferableId
0x00040000	3.0.0-5	GetRegionCanadaUSA/IsCoppacsSupported
0x00050000	5.0.0-11	GetSystemModel
0x00060000	6.0.0-11	GetModelNintendo2DS
0x00070040	7.0.0-13	(u8 val) This writes the input u8 to the first byte in the config-block for blkID 0x00160000.
0x00080080	7.0.0-13	TranslateCountryInfo
0x00090040	7.0.0-13	GetCountryCodeString
0x000A0040	7.0.0-13	GetCountryCodeID
0x000B0000	9.3.0-X	IsFangateSupported

Config service "cfg:s"

cfg:s contains all the commands in cfg:u, in addition to the following:

Command Header	Available since system version	Description
0x00050000		Same as cfg:u 0x00050000 cmd?
0x04010082		GetConfigInfoBlk8
0x04020082		SetConfigInfoBlk4
0x04030000		UpdateConfigNANDSavegame
0x04040042		GetLocalFriendCodeSeedData
0x04050000		GetLocalFriendCodeSeed
0x04060000		SecureInfoGetRegion
0x04070000		SecureInfoGetByte101
0x04080042		SecureInfoGetSerialNo
0x04090000		UpdateConfigBlk00040003
0x040A0000	?	?
0x040B0000	?	?
0x040C0000	?	?
0x040D0040	?	?
0x040E0000	?	?
0x040F0000		ClearParentalControls

CfgS command 0x04060000(SecureInfoGetRegion) is used by NIM module to determine the SOAP RegionId, when sending SOAP requests. See here.

cfg:i contains all the commands in cfg:u and cfg:s, in addition to the following:

Command Header	Available since system version	Description
0x08010082		GetConfigInfoBlk8
0x08020082		SetConfigInfoBlk4
0x08030000		UpdateConfigNANDSavegame
0x080400C2		CreateConfigInfoBlk
0x08050000		DeleteConfigNANDSavefile
0x08060000		FormatConfig
0x08070000		This basically just returns result-code value 0x0, due to code this eventually executes being NOPed out.
0x08080000		This updates the config blocks for blkIDs 0x0 and 0x20000. In certain cases this may call the code for FormatConfig.
0x08090000		This updates the config block for blkID 0x60000.
0x080A0000		ResetAnalogStickCalibrationParam? This updates the config block for blkID 0x00040001.
0x080B0082		SetGetLocalFriendCodeSeedData
0x080C0042		SetLocalFriendCodeSeedSignature
0x080D0000		DeleteCreateNANDLocalFriendCodeSeed
0x080E0000		VerifySigLocalFriendCodeSeed
0x080F0042		GetLocalFriendCodeSeedData
0x08100000		GetLocalFriendCodeSeed
0x08110084		SetSecureInfo
0x08120000		DeleteCreateNANDSecureInfo
0x08130000		VerifySigSecureInfo
0x08140042		SecureInfoGetData
0x08150042		SecureInfoGetSignature
0x08160000		SecureInfoGetRegion
0x08170000		SecureInfoGetByte101
0x08180042		SecureInfoGetSerialNo
0x0819....	?	?
0x081A....	?	?
0x081B....	?	?
0x081C....	?	?
0x081D....	?	?
0x081E....	?	?
0x081F....	?	?
0x0820....	?	?

Command Header	Description
0x00010040	Initialize
0x00020000	Shutdown
0x00030040	(u8 flag) Writes the input flag to state. Uses SPI service command EnableSpiBus.
0x00040000	Writes the u8 from the state written by 0x00030040 to cmdreply[2].
0x00050082	ReadData
0x00060082	WriteData
0x00070000	This just uses the WREN command.
0x00080000	This just uses the WRDI command.
0x00090000	ReadIdentification
0x000A0000	This waits for the WIP bit in the status register to clear(wait for writing to finish).
0x000B0000	This waits for the WEL bit in the status register to become set(write enabled).
0x000C0000	This writes the value of the WIP bit in the status register to u8 cmdreply[2].
0x000D0000	This writes the value of the WIP bit in the status register to u8 cmdreply[2].
0x000E0000	ReadStatusRegister
0x000F0082	ReadDataOther
0x00100082	WriteDataOther
0x00110040	(u32 offset) Uses command WREN then waits for WEL to become enabled. Sends command 0xDB to SPI followed by the specified flash offset.
0x00120040	(u32 offset) Identical to 0x00110040 except this uses SPI-command 0xD8 instead("block erase").
0x00130000	This uses SPI command 0xB9 for "Deep power down".
0x00140000	This uses SPI command 0xAB for "Release from deep power down".

This is an interface for the "SPI::NOR" service, for accessing the Wifi NVRAM/SPI Flash.