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;;                                                              ;;

;; Copyright (C) KolibriOS team 2013. All rights reserved.      ;;

;; Distributed under terms of the GNU General Public License    ;;

;;                                                              ;;

;; RAMDISK functions                                            ;;

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$Revision: 4287 $

iglobal

align 4

ramdisk_functions:

        dd      .size

        dd      0       ; no close() function

        dd      0       ; no closemedia() function

        dd      ramdisk_querymedia

        dd      ramdisk_read

        dd      ramdisk_write

        dd      0       ; no flush() function

        dd      ramdisk_adjust_cache_size

.size = $ - ramdisk_functions

endg

; See memmap.inc.

; Currently size of memory allocated for the ramdisk is fixed.

; This should be revisited when/if memory map would become more dynamic.

RAMDISK_CAPACITY = 2880 ; in sectors

iglobal

align 4

ramdisk_actual_size     dd      RAMDISK_CAPACITY

endg

; This function is called early in boot process.

; It creates filesystem /rd/1 based on raw image data loaded by somebody before

; to memory named as RAMDISK with max size RAMDISK_CAPACITY, may be less.

proc ramdisk_init

iglobal

ramdisk_name    db      'rd',0

endg

        push    ebx esi ; save used registers to be stdcall

; 1. Register the device and the (always inserted) media in the disk subsystem.

        stdcall disk_add, ramdisk_functions, ramdisk_name, 0, 0

        test    eax, eax

        jz      .fail

        mov     ebx, eax

        stdcall disk_media_changed, eax, 1

; 2. We don't know actual size of loaded image,

; so try to calculate it using partition structure,

; assuming that file systems fill the real size based on contents of the partition.

; 2a. Prepare for loop over partitions.

        xor     ecx, ecx

        xor     edx, edx

; 2b. Check that at least one partition was recognized.

        cmp     [ebx+DISK.NumPartitions], ecx

        jz      .fail

; 2c. Loop over partitions.

.partitions:

; For every partition, set edx to maximum between edx and end of partition.

        mov     esi, [ebx+DISK.Partitions]

        mov     esi, [esi+ecx*4]

        mov     eax, dword [esi+PARTITION.FirstSector]

        add     eax, dword [esi+PARTITION.Length]

        cmp     eax, edx

        jb      @f

        mov     edx, eax

@@:

        inc     ecx

        cmp     ecx, [ebx+DISK.NumPartitions]

        jb      .partitions

; 3. Reclaim unused memory, if any.

        mov     [ramdisk_actual_size], edx

        add     edx, 7  ; aligning up

        shr     edx, 3  ; 512-byte sectors -> 4096-byte pages

        mov     esi, RAMDISK_CAPACITY / 8       ; aligning down

        sub     esi, edx

        jbe     .no_reclaim

        shl     edx, 12

        add     edx, RAMDISK - OS_BASE

@@:

        mov     eax, edx

        call    free_page

        add     edx, 0x1000

        dec     esi

        jnz     @b

.no_reclaim:

        pop     esi ebx ; restore used registers to be stdcall

        ret

.fail:

        dbgstr 'Failed to initialize ramdisk'

        pop     esi ebx ; restore used registers to be stdcall

        ret

endp

; Returns information about disk media.

proc ramdisk_querymedia

  virtual at esp+4

    .userdata dd ?

    .info dd ?

  end virtual

; Media is always present, sector size is always 512 bytes.

        mov     edx, [.userdata]

        mov     ecx, [.info]

        mov     [ecx+DISKMEDIAINFO.Flags], 0

        mov     [ecx+DISKMEDIAINFO.SectorSize], 512

        mov     eax, [ramdisk_actual_size]

        mov     dword [ecx+DISKMEDIAINFO.Capacity], eax

        mov     dword [ecx+DISKMEDIAINFO.Capacity+4], 0

; Return zero as an indicator of success.

        xor     eax, eax

        retn    8

endp

; Common procedure for reading and writing.

; operation = 0 for reading, operation = 1 for writing.

; Arguments of ramdisk_read and ramdisk_write are the same.

macro ramdisk_read_write operation

{

        push    esi edi         ; save used registers to be stdcall

        mov     esi, [userdata]

        mov     edi, [numsectors_ptr]

; 1. Determine number of sectors to be transferred.

; This is either the requested number of sectors or number of sectors

; up to the disk boundary, depending of what is less.

        xor     ecx, ecx

; 1a. Test whether [start_sector] is less than RAMDISK_CAPACITY.

; If so, calculate number of sectors between [start_sector] and RAMDISK_CAPACITY.

; Otherwise, the actual number of sectors is zero.

        cmp     dword [start_sector+4], ecx

        jnz     .got_number

        mov     eax, [ramdisk_actual_size]

        sub     eax, dword [start_sector]

        jbe     .got_number

; 1b. Get the requested number of sectors.

        mov     ecx, [edi]

; 1c. If it is greater than number of sectors calculated in 1a, use the value

; from 1a.

        cmp     ecx, eax

        jb      .got_number

        mov     ecx, eax

.got_number:

; 2. Compare the actual number of sectors with requested. If they are

; equal, set eax (it will be the returned value) to zero. Otherwise,

; use DISK_STATUS_END_OF_MEDIA.

        xor     eax, eax

        cmp     ecx, [edi]

        jz      @f

        mov     al, DISK_STATUS_END_OF_MEDIA

@@:

; 3. Store the actual number of sectors.

        mov     [edi], ecx

; 4. Calculate source and destination addresses.

if operation = 0 ; reading?

        mov     esi, dword [start_sector]

        shl     esi, 9

        add     esi, RAMDISK

        mov     edi, [buffer]

else ; writing?

        mov     edi, dword [start_sector]

        shl     edi, 9

        add     edi, RAMDISK

        mov     esi, [buffer]

end if

; 5. Calculate number of dwords to be transferred.

        shl     ecx, 9-2

; 6. Copy data.

        rep movsd

; 7. Return. The value in eax was calculated in step 2.

        pop     edi esi         ; restore used registers to be stdcall

}

; Reads one or more sectors from the device.

proc ramdisk_read userdata:dword, buffer:dword, start_sector:qword, numsectors_ptr:dword

        ramdisk_read_write 0

        ret

endp

; Writes one or more sectors to the device.

proc ramdisk_write userdata:dword, buffer:dword, start_sector:qword, numsectors_ptr:dword

        ramdisk_read_write 1

        ret

endp

; The kernel calls this function when initializing cache subsystem for

; the media. This call allows the driver to adjust the cache size.

proc ramdisk_adjust_cache_size

  virtual at esp+4

    .userdata dd ?

    .suggested_size dd ?

  end virtual

; Since ramdisk does not need cache, just return 0.

        xor     eax, eax

        retn    8

endp