Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 4180f24a authored by Brian Norris's avatar Brian Norris Committed by Artem Bityutskiy
Browse files

mtd: document ABI 



We're missing a lot of important documentation in include/mtd/mtd-abi.h:

* add a simple description of each ioctl (feel free to expand!)
* give full explanations of recently added and modified operations
* explain the usage of "RAW" that appear in different modes and types of
  operations
* fix some comment style along the way

Signed-off-by: default avatarBrian Norris <computersforpeace@gmail.com>
Signed-off-by: default avatarArtem Bityutskiy <artem.bityutskiy@intel.com>
parent e99d8b08

include/linux/mtd/mtd.h

+1 −1
Original line number Diff line number Diff line
@@ -79,7 +79,7 @@ struct mtd_erase_region_info { 
 * @ooblen:	number of oob bytes to write/read

 * @oobretlen:	number of oob bytes written/read

 * @ooboffs:	offset of oob data in the oob area (only relevant when

 *		mode = MTD_OPS_PLACE_OOB)

 *		mode = MTD_OPS_PLACE_OOB or MTD_OPS_RAW)

 * @datbuf:	data buffer - if NULL only oob data are read/written

 * @oobbuf:	oob data buffer

 *

include/mtd/mtd-abi.h

+73 −13
Original line number Diff line number Diff line
@@ -45,14 +45,18 @@ struct mtd_oob_buf64 { 
	__u64 usr_ptr;

};



/*

/**

 * MTD operation modes

 *

 * MTD_OPS_PLACE_OOB:	oob data are placed at the given offset (default)

 * MTD_OPS_AUTO_OOB:	oob data are automatically placed at the free areas

 * @MTD_OPS_PLACE_OOB:	OOB data are placed at the given offset (default)

 * @MTD_OPS_AUTO_OOB:	OOB data are automatically placed at the free areas

 *			which are defined by the internal ecclayout

 * MTD_OPS_RAW:		mode to read or write oob and data without doing ECC

 *			checking

 * @MTD_OPS_RAW:	data are transferred as-is, with no error correction;

 *			this mode implies %MTD_OPS_PLACE_OOB

 *

 * These modes can be passed to ioctl(MEMWRITE) and are also used internally.

 * See notes on "MTD file modes" for discussion on %MTD_OPS_RAW vs.

 * %MTD_FILE_MODE_RAW.

 */

enum {

	MTD_OPS_PLACE_OOB = 0,
@@ -60,6 +64,22 @@ enum { 
	MTD_OPS_RAW = 2,

};



/**

 * struct mtd_write_req - data structure for requesting a write operation

 *

 * @start:	start address

 * @len:	length of data buffer

 * @ooblen:	length of OOB buffer

 * @usr_data:	user-provided data buffer

 * @usr_oob:	user-provided OOB buffer

 * @mode:	MTD mode (see "MTD operation modes")

 * @padding:	reserved, must be set to 0

 *

 * This structure supports ioctl(MEMWRITE) operations, allowing data and/or OOB

 * writes in various modes. To write to OOB-only, set @usr_data == NULL, and to

 * write data-only, set @usr_oob == NULL. However, setting both @usr_data and

 * @usr_oob to NULL is not allowed.

 */

struct mtd_write_req {

	__u64 start;

	__u64 len;
@@ -84,13 +104,13 @@ struct mtd_write_req { 
#define MTD_NO_ERASE		0x1000	/* No erase necessary */

#define MTD_POWERUP_LOCK	0x2000	/* Always locked after reset */



// Some common devices / combinations of capabilities

/* Some common devices / combinations of capabilities */

#define MTD_CAP_ROM		0

#define MTD_CAP_RAM		(MTD_WRITEABLE | MTD_BIT_WRITEABLE | MTD_NO_ERASE)

#define MTD_CAP_NORFLASH	(MTD_WRITEABLE | MTD_BIT_WRITEABLE)

#define MTD_CAP_NANDFLASH	(MTD_WRITEABLE)



/* ECC byte placement */

/* Obsolete ECC byte placement modes (used with obsolete MEMGETOOBSEL) */

#define MTD_NANDECC_OFF		0	// Switch off ECC (Not recommended)

#define MTD_NANDECC_PLACE	1	// Use the given placement in the structure (YAFFS1 legacy mode)

#define MTD_NANDECC_AUTOPLACE	2	// Use the default placement scheme
@@ -105,10 +125,10 @@ struct mtd_write_req { 
struct mtd_info_user {

	__u8 type;

	__u32 flags;

	__u32 size;	 // Total size of the MTD

	__u32 size;	/* Total size of the MTD */

	__u32 erasesize;

	__u32 writesize;

	__u32 oobsize;   // Amount of OOB data per block (e.g. 16)

	__u32 oobsize;	/* Amount of OOB data per block (e.g. 16) */

	/* The below two fields are obsolete and broken, do not use them

	 * (TODO: remove at some point) */

	__u32 ecctype;
@@ -135,28 +155,54 @@ struct otp_info { 
 * Try to avoid adding a new ioctl with the same ioctl number.

 */



/* Get basic MTD characteristics info (better to use sysfs) */

#define MEMGETINFO		_IOR('M', 1, struct mtd_info_user)

/* Erase segment of MTD */

#define MEMERASE		_IOW('M', 2, struct erase_info_user)

/* Write out-of-band data from MTD */

#define MEMWRITEOOB		_IOWR('M', 3, struct mtd_oob_buf)

/* Read out-of-band data from MTD */

#define MEMREADOOB		_IOWR('M', 4, struct mtd_oob_buf)

/* Lock a chip (for MTD that supports it) */

#define MEMLOCK			_IOW('M', 5, struct erase_info_user)

/* Unlock a chip (for MTD that supports it) */

#define MEMUNLOCK		_IOW('M', 6, struct erase_info_user)

/* Get the number of different erase regions */

#define MEMGETREGIONCOUNT	_IOR('M', 7, int)

/* Get information about the erase region for a specific index */

#define MEMGETREGIONINFO	_IOWR('M', 8, struct region_info_user)

/* Get info about OOB modes (e.g., RAW, PLACE, AUTO) - legacy interface */

#define MEMGETOOBSEL		_IOR('M', 10, struct nand_oobinfo)

/* Check if an eraseblock is bad */

#define MEMGETBADBLOCK		_IOW('M', 11, __kernel_loff_t)

/* Mark an eraseblock as bad */

#define MEMSETBADBLOCK		_IOW('M', 12, __kernel_loff_t)

/* Set OTP (One-Time Programmable) mode (factory vs. user) */

#define OTPSELECT		_IOR('M', 13, int)

/* Get number of OTP (One-Time Programmable) regions */

#define OTPGETREGIONCOUNT	_IOW('M', 14, int)

/* Get all OTP (One-Time Programmable) info about MTD */

#define OTPGETREGIONINFO	_IOW('M', 15, struct otp_info)

/* Lock a given range of user data (must be in mode %MTD_FILE_MODE_OTP_USER) */

#define OTPLOCK			_IOR('M', 16, struct otp_info)

/* Get ECC layout (deprecated) */

#define ECCGETLAYOUT		_IOR('M', 17, struct nand_ecclayout_user)

/* Get statistics about corrected/uncorrected errors */

#define ECCGETSTATS		_IOR('M', 18, struct mtd_ecc_stats)

/* Set MTD mode on a per-file-descriptor basis (see "MTD file modes") */

#define MTDFILEMODE		_IO('M', 19)

/* Erase segment of MTD (supports 64-bit address) */

#define MEMERASE64		_IOW('M', 20, struct erase_info_user64)

/* Write data to OOB (64-bit version) */

#define MEMWRITEOOB64		_IOWR('M', 21, struct mtd_oob_buf64)

/* Read data from OOB (64-bit version) */

#define MEMREADOOB64		_IOWR('M', 22, struct mtd_oob_buf64)

/* Check if chip is locked (for MTD that supports it) */

#define MEMISLOCKED		_IOR('M', 23, struct erase_info_user)

/*

 * Most generic write interface; can write in-band and/or out-of-band in various

 * modes (see "struct mtd_write_req")

 */

#define MEMWRITE		_IOWR('M', 24, struct mtd_write_req)



/*
@@ -208,7 +254,21 @@ struct mtd_ecc_stats { 
};



/*

 * Read/write file modes for access to MTD

 * MTD file modes - for read/write access to MTD

 *

 * @MTD_FILE_MODE_NORMAL:	OTP disabled, ECC enabled

 * @MTD_FILE_MODE_OTP_FACTORY:	OTP enabled in factory mode

 * @MTD_FILE_MODE_OTP_USER:	OTP enabled in user mode

 * @MTD_FILE_MODE_RAW:		OTP disabled, ECC disabled

 *

 * These modes can be set via ioctl(MTDFILEMODE). The mode mode will be retained

 * separately for each open file descriptor.

 *

 * Note: %MTD_FILE_MODE_RAW provides the same functionality as %MTD_OPS_RAW -

 * raw access to the flash, without error correction or autoplacement schemes.

 * Wherever possible, the MTD_OPS_* mode will override the MTD_FILE_MODE_* mode

 * (e.g., when using ioctl(MEMWRITE)), but in some cases, the MTD_FILE_MODE is

 * used out of necessity (e.g., `write()', ioctl(MEMWRITEOOB64)).

 */

enum mtd_file_modes {

	MTD_FILE_MODE_NORMAL = MTD_OTP_OFF,