[PATCH 09/12] mtd: document ABI
Brian Norris
computersforpeace at gmail.com
Tue Aug 30 21:45:44 EDT 2011
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: Brian Norris <computersforpeace at gmail.com>
---
include/linux/mtd/mtd.h | 2 +-
include/mtd/mtd-abi.h | 86 +++++++++++++++++++++++++++++++++++++++-------
2 files changed, 74 insertions(+), 14 deletions(-)
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index e02e65b..ead70ed 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -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
*
diff --git a/include/mtd/mtd-abi.h b/include/mtd/mtd-abi.h
index 0a21ef5..d54ccf3 100644
--- a/include/mtd/mtd-abi.h
+++ b/include/mtd/mtd-abi.h
@@ -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;
__u32 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;
@@ -117,9 +137,9 @@ struct mtd_info_user {
struct region_info_user {
__u32 offset; /* At which this region starts,
- * from the beginning of the MTD */
- __u32 erasesize; /* For this region */
- __u32 numblocks; /* Number of blocks in this region */
+ * from the beginning of the MTD */
+ __u32 erasesize; /* For this region */
+ __u32 numblocks; /* Number of blocks in this region */
__u32 regionindex;
};
@@ -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,
--
1.7.5.4
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