x68000:writing_drivers
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The following information was kindly contributed by our forum member **Lydux**. | The following information was kindly contributed by our forum member **Lydux**. | ||
+ | |||
+ | Original thread can be found here: | ||
+ | http:// | ||
So I've decided to share with you some of my study and work. | So I've decided to share with you some of my study and work. | ||
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**Note :** the following contains very hard stuff ! I might be confusing sometimes, sorry in advance. Don't hesitate to ask for help if you do not understand something. Thank you. | **Note :** the following contains very hard stuff ! I might be confusing sometimes, sorry in advance. Don't hesitate to ask for help if you do not understand something. Thank you. | ||
- | |||
**Terminology :** | **Terminology :** | ||
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* Char : 1 character = 1 byte | * Char : 1 character = 1 byte | ||
* All data types are CPU specific : M68K family. So, byte ordering is always "Big Endian" | * All data types are CPU specific : M68K family. So, byte ordering is always "Big Endian" | ||
- | |||
====== Compilation flags, libraries and startup code ====== | ====== Compilation flags, libraries and startup code ====== | ||
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The small allocated kernel memory area will change on every kernel request. Only the first 13 bytes is a fixed structure describing the request itself, and the remaining are the request parameters. Note that the some Request Packet structure members are filled by the kernel (input), others are by the drivers as the result of the request (output). | The small allocated kernel memory area will change on every kernel request. Only the first 13 bytes is a fixed structure describing the request itself, and the remaining are the request parameters. Note that the some Request Packet structure members are filled by the kernel (input), others are by the drivers as the result of the request (output). | ||
+ | |||
Request packet structure header (fixed first 13 bytes) : | Request packet structure header (fixed first 13 bytes) : | ||
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**Command execution result flags :** | **Command execution result flags :** | ||
- | This list contains all acceptable values to fill the result status flags in the request packet header. S_**** flags will display (or hide) the " | + | This list contains all acceptable values to fill the result status flags in the request packet header. S_**** flags will display (or hide) the " |
+ | |||
+ | " | ||
* 0x1000 - S_ABORT : " | * 0x1000 - S_ABORT : " | ||
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* 0x000D - E_WRPRT : Write Protect | * 0x000D - E_WRPRT : Write Protect | ||
* 0x000E - E_DISK : Disk Change | * 0x000E - E_DISK : Disk Change | ||
+ | |||
+ | ====== Generic command codes and parameters ====== | ||
+ | |||
+ | Each possible request command code in the request packet header have their own set of parameters. Again some are filled by the kernel, and others by the driver. | ||
+ | |||
+ | Note that some request command code are available only for character device drivers, some only for block device drivers and some on both. Remote device drivers have their own set of command code. | ||
+ | Command parameters structure always start at position 14 within the request packet. | ||
+ | |||
+ | ===== 0x00 - Initialize ===== | ||
+ | |||
+ | **Command ID :** 0x00 (C_INIT) | ||
+ | |||
+ | **Availability :** Block/ | ||
+ | |||
+ | **Description :** | ||
+ | |||
+ | This is the initialize command and is called only once after driver loading. On initialize, the driver must perform eventual device detection and initialization, | ||
+ | |||
+ | **Input parameters :** | ||
+ | |||
+ | ^ Position | ||
+ | | 18 | Long |Pointer to a null terminated string containing arguments passed via CONFIG.SYS | ||
+ | | 22 | Byte |Block device driver only. Not sure of the meaning, but this probably contains the drive number the kernel want to initialize. | ||
+ | |||
+ | |||
+ | **Output parameters :** | ||
+ | |||
+ | ^ Position | ||
+ | | 13 | Byte |Block device driver only. The amount of " | ||
+ | | 14 | Long |Pointer to the end of the used memory space. This memory space include every segment sizes used by the driver : TEXT, DATA, BSS, as well as eventual HEAP. A very important parameter ! Any wrong value written here will crash the kernel. Normally, my toolchain provides a symbol usable for this parameter : " | ||
+ | | 18 | Long |Block device driver only. Pointer to an array of BPB (Bios Parameter Block). Basically, a BPB describes the FAT volume on the physical disk, so determine the size of a partition or media. For more information about BPB, see wikipedia : http:// | ||
+ | |||
+ | ===== 0x01 - Media Check ===== | ||
+ | |||
+ | **Command ID :** 0x01 (C_MEDIACHK) | ||
+ | |||
+ | **Availability :** Block | ||
+ | |||
+ | **Description :** Before performing IO operations on a block device, the kernel will process this command code to ensure the target media is still available and ready. | ||
+ | |||
+ | **Input parameters :** | ||
+ | |||
+ | ^ Position | ||
+ | | 13 | Byte |Last known media type ID. See standard media type list bellow. | ||
+ | |||
+ | |||
+ | **Output parameters :** | ||
+ | |||
+ | ^ Position | ||
+ | | 14 | Byte |Media status. Possible values are : | | ||
+ | | | -1 |M_CHANGED : Media was changed | ||
+ | | | 0 |M_DONT_KNOW : Media state unknown | ||
+ | | | 1 |M_NOT_CHANGED : Media still in and ready | | ||
+ | |||
+ | **Human68K standard media type list :** | ||
+ | |||
+ | Note : this list isn't exhaustive ! A driver can provide its own set. So, a program or driver should never rely on these values to determine the media type. | ||
+ | |||
+ | I will not explain them, names pretty much speak for themselves. | ||
+ | |||
+ | * 0xE0 - MD_2DD_10 | ||
+ | * 0xE5 - MD_1D_9 | ||
+ | * 0xE6 - MD_2D_9 | ||
+ | * 0xE7 - MD_1D_8 | ||
+ | * 0xE8 - MD_2D_8 | ||
+ | * 0xEA - MD_2HT | ||
+ | * 0xEB - MD_2HS | ||
+ | * 0xEC - MD_2HDE | ||
+ | * 0xEE - MD_1DD_9 | ||
+ | * 0xEF - MD_1DD_8 | ||
+ | * 0xF4 - MD_DAT | ||
+ | * 0xF5 - MD_CDROM | ||
+ | * 0xF6 - MD_MO | ||
+ | * 0xF7 - MD_SCSIHD | ||
+ | * 0xF8 - MD_SASIHD | ||
+ | * 0xF9 - MD_RAMDISK | ||
+ | * 0xFA - MD_2HQ | ||
+ | * 0xFB - MD_2DD_8 | ||
+ | * 0xFC - MD_2DD_9 | ||
+ | * 0xFD - MD_2HC | ||
+ | * 0xFE - MD_2HD | ||
+ | |||
+ | |||
+ | ===== 0x02 - Build BPB ===== | ||
+ | |||
+ | |||
+ | **Command ID :** 0x02 (C_BLDBPB) | ||
+ | |||
+ | **Availability :** Block | ||
+ | |||
+ | **Description :** This command is proceed when a media have previously been reported as " | ||
+ | |||
+ | **Input parameters :** none | ||
+ | |||
+ | **Output parameters :** | ||
+ | |||
+ | ^ Position | ||
+ | | 18 | Long | Pointer to the requested unit BPB | | ||
+ | |||
+ | |||
+ | ===== 0x03 - IOCTL input ===== | ||
+ | |||
+ | **Command ID :** 0x03 (C_IOCTLIN) | ||
+ | |||
+ | **Availability :** Block/ | ||
+ | |||
+ | **Description :** Request the driver to read raw arbitrary datas from the specified unit. This request is initiated by an userspace application (IOCTL). | ||
+ | |||
+ | **Input parameters :** | ||
+ | |||
+ | ^ Position | ||
+ | | 14 | Long |Pointer to a buffer that' | ||
+ | | 18 | Long |Buffer size | | ||
+ | |||
+ | **Output parameters :** none | ||
+ | |||
+ | ===== 0x04 - Input (read) ===== | ||
+ | |||
+ | **Command ID :** 0x04 (C_INPUT) | ||
+ | |||
+ | **Availability :** Block/ | ||
+ | |||
+ | **Description :** Request the driver to read data from the specified unit. This request is initiated by the kernel. | ||
+ | |||
+ | **Input parameters :** | ||
+ | |||
+ | ^ Position | ||
+ | | 13 | Byte |Block device driver only. Media type. | | ||
+ | | 14 | Long |Pointer to a buffer that' | ||
+ | | 18 | Long |Block device driver : number of sector to read. A sector length is normally specified by the BPB. | | ||
+ | | | |Character device driver : Buffer size. | | ||
+ | | 22 | Long |Block device driver only : logical start sector to read from. | | ||
+ | |||
+ | **Output parameters :** none | ||
+ | |||
+ | Note for block device driver : as the kernel is responsible for handling the FAT, you just have to seek to the specified start sector location and read the wanted amount of data from there according to the requested amount of sectors and the BPB. However, the driver is still responsible of the logical to physical partition translation ! So, seek correctly. | ||
+ | |||
+ | ===== 0x05 - Read no wait ===== | ||
+ | |||
+ | **Command ID :** 0x05 (C_NDREAD) | ||
+ | |||
+ | **Availability :** Character | ||
+ | |||
+ | **Description :** To check furthermore. A strange command code that allow a driver to send back a device prereaded byte. Maybe dedicated command to some simple interrupt driven device. | ||
+ | |||
+ | **Input parameters :** none | ||
+ | |||
+ | **Output parameters :** | ||
+ | |||
+ | ^ Position | ||
+ | | 13 | Byte |Prereaded byte | | ||
+ | |||
+ | ===== 0x05 - Drive control/ | ||
+ | |||
+ | **Command ID :** 0x05 (C_DRVCTL) | ||
+ | |||
+ | **Availability :** Block | ||
+ | |||
+ | **Description :** //To check furthermore.// | ||
+ | |||
+ | ===== 0x06 - Input status ===== | ||
+ | |||
+ | **Command ID :** 0x06 (C_ISTAT) | ||
+ | |||
+ | **Availability :** Character | ||
+ | |||
+ | **Description :** Kernel perform this command before the INPUT one to check if reading on the specified unit is actually possible or not. There is no parameter. Just fill the result flags in the request packet header accordingly. | ||
+ | |||
+ | **Input parameters :** none | ||
+ | |||
+ | **Output parameters :** none | ||
+ | |||
+ | ===== 0x07 - Input flush ===== | ||
+ | |||
+ | **Command ID :** 0x07 (C_IFLUSH) | ||
+ | |||
+ | **Availability :** Character | ||
+ | |||
+ | **Description :** Request the driver to flush the specified unit input buffer. There is no parameter. Just fill the result flags in the request packet header accordingly. | ||
+ | |||
+ | **Input parameters :** none | ||
+ | |||
+ | **Output parameters :** none | ||
+ | |||
+ | ===== 0x08 - Output (write) ===== | ||
+ | |||
+ | **Command ID :** 0x08 (C_OUTPUT) | ||
+ | |||
+ | **Availability :** Block/ | ||
+ | |||
+ | **Description :** Request the driver to write data to a specified unit. This request is initiated by the kernel. | ||
+ | |||
+ | **Input parameters :** | ||
+ | |||
+ | ^ Position | ||
+ | | 14 | Long |Pointer to a buffer that contains data to write to the unit.| | ||
+ | | 18 | Long |Block device driver : number of sector to write. A sector length is normally specified by the BPB. | | ||
+ | | | |Character device driver : Buffer size. | | ||
+ | | 22 | Long |Block device driver only : logical start sector to write to. | | ||
+ | |||
+ | **Output parameters :** none | ||
+ | |||
+ | Note for block device driver : as the kernel is responsible for handling the FAT, you just have to seek to the specified start sector location and read the wanted amount of data from there according to the requested amount of sectors and the BPB. However, the driver is still responsible of the logical to physical partition translation ! So, seek correctly. | ||
+ | |||
+ | ===== 0x09 - Output with verify ===== | ||
+ | |||
+ | **Command ID :** 0x09 (C_OUTVFY) | ||
+ | |||
+ | **Availability :** Block/ | ||
+ | |||
+ | **Description :** Same as "0x08 - Output (write)", | ||
+ | |||
+ | **Input parameters :** same as the "0x08 - Output (write)" | ||
+ | |||
+ | ===== 0x0A - Output status ===== | ||
+ | |||
+ | **Command ID :** 0x0A (C_OSTAT) | ||
+ | |||
+ | **Availability :** Character | ||
+ | |||
+ | **Description :** Kernel perform this command before the OUTPUT one to check if writing to the specified unit is actually possible or not. There is no parameter. Just fill the result flags in the request packet header accordingly. | ||
+ | |||
+ | **Input parameters :** none | ||
+ | |||
+ | **Output parameters :** none | ||
+ | |||
+ | ===== 0x0B - Output flush ===== | ||
+ | |||
+ | **Command ID :** 0x0B (C_OFLUSH) | ||
+ | |||
+ | **Availability :** Character | ||
+ | |||
+ | **Description :** Request the driver to flush the specified unit output buffer. There is no parameter. Just fill the result flags in the request packet header accordingly. | ||
+ | |||
+ | **Input parameters :** none | ||
+ | |||
+ | **Output parameters :** none | ||
+ | |||
+ | ===== 0x0C - IOCTL out ===== | ||
+ | |||
+ | **Command ID :** 0x0C (C_IOCTLOUT) | ||
+ | |||
+ | **Availability :** Block/ | ||
+ | |||
+ | **Description :** Request the driver to write raw arbitrary datas to the specified unit. This request is initiated by an userspace application (IOCTL). | ||
+ | |||
+ | **Input parameters :** | ||
+ | |||
+ | ^ Position | ||
+ | | 14 | Long |Pointer to a buffer that' | ||
+ | | 18 | Long |Buffer size | | ||
+ | |||
+ | **Output parameters :** none | ||
+ | |||
+ | ===== 0x13 - Generic IOCTL ===== | ||
+ | |||
+ | **Command ID :** 0x13 (C_GENIOCTL) | ||
+ | |||
+ | **Availability :** Block/ | ||
+ | |||
+ | **Description :** Perform a IOCTL command understood only by the driver and an userspace program. | ||
+ | |||
+ | **Input parameters :** | ||
+ | |||
+ | ^ Position | ||
+ | | 14 | Long |Optional pointer to a buffer. That buffer is totally specific to the IOCTL command ID. | | ||
+ | | 18 | Word |IOCTL command ID. There is no restriction to this value. | ||
+ | |||
+ | **Output parameters :** none | ||
+ | |||
+ | ====== Extend command code ====== | ||
+ | |||
+ | These following request command codes are only performed when the driver header have the " | ||
+ | |||
+ | I actually do not know very much about them but they seems to be really filesystem level. | ||
+ | |||
+ | Here is all known command ID : | ||
+ | |||
+ | * 0x40 - CR_INIT | ||
+ | * 0x41 - CR_SEARCH_DIR | ||
+ | * 0x42 - CR_CREATE_DIR | ||
+ | * 0x43 - CR_DELETE_DIR | ||
+ | * 0x44 - CR_RENAME_FILE | ||
+ | * 0x45 - CR_DELETE_FILE | ||
+ | * 0x46 - CR_CHMOD | ||
+ | * 0x47 - CR_FILES | ||
+ | * 0x48 - CR_NFILES | ||
+ | * 0x49 - CR_CREATE | ||
+ | * 0x4A - CR_OPEN | ||
+ | * 0x4B - CR_CLOS | ||
+ | * 0x4C - CR_READ | ||
+ | * 0x4D - CR_WRITE | ||
+ | * 0x4E - CR_SEEK | ||
+ | * 0x4F - CR_TIMEMOD | ||
+ | * 0x50 - CR_GETCAP | ||
+ | * 0x51 - CR_CONTROL | ||
+ | * 0x52 - CR_BUILD_BPB | ||
+ | * 0x53 - CR_IOCTL_IN | ||
+ | * 0x54 - CR_IOCTL_OUT | ||
+ | * 0x55 - CR_IOCTL_SPECIAL | ||
+ | * 0x56 - CR_ABORT | ||
+ | * 0x57 - CR_MEDIA_CHECK | ||
+ | * 0x58 - CR_LOCK | ||
+ | |||
+ | I do have parameters. I will write them later. | ||
+ | |||
+ | |||
+ | ====== BIOS Parameter Block (BPB) ====== | ||
+ | |||
+ | I will not explain this structure as there is plenty of informations about it on the internet. | ||
+ | |||
+ | Starting from wikipedia : http:// | ||
+ | |||
+ | Just read everything you can about FAT12 and FAT16. 95% of these also apply to Human68k. | ||
+ | |||
+ | Most of difference is the byte ordering, which is big endian instead of little endian. The structure is also a bit different. | ||
+ | |||
+ | From my ddk.h file : | ||
+ | |||
+ | < | ||
+ | struct bpb { | ||
+ | UWORD bpb_nbyte; | ||
+ | UBYTE bpb_nsector; | ||
+ | UBYTE bpb_nfat; | ||
+ | UWORD bpb_nreserved; | ||
+ | UWORD bpb_ndirent; | ||
+ | UWORD bpb_nsize; | ||
+ | UBYTE bpb_mdesc; | ||
+ | UBYTE bpb_nfsect; | ||
+ | ULONG bpb_huge; | ||
+ | }; | ||
+ | </ | ||
+ | |||
+ | See ? Only the " | ||
+ |
x68000/writing_drivers.1404989361.txt.gz · Last modified: 2019/08/27 20:44 (external edit)