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;; Copyright (C) KolibriOS team 2013-2024. All rights reserved. ;;

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

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; Memory management for USB structures.

; Protocol layer uses the common kernel heap malloc/free.

; Hardware layer has special requirements:

; * memory blocks should be properly aligned

; * memory blocks should not cross page boundary

; Hardware layer allocates fixed-size blocks.

; Thus, hardware layer uses the system slab allocator.

; Helper procedure: translate physical address in ecx

; of some transfer descriptor to linear address.

; in: eax = address of first page

proc usb_td_to_virt

; Traverse all pages used for transfer descriptors, looking for the one

; with physical address as in ecx.

@@:

        test    eax, eax

        jz      .zero

        push    eax

        call    get_pg_addr

        sub     eax, ecx

        jz      .found

        cmp     eax, -0x1000

        ja      .found

        pop     eax

        mov     eax, [eax+0x1000-4]

        jmp     @b

.found:

; When found, combine page address from eax with page offset from ecx.

        pop     eax

        and     ecx, 0xFFF

        add     eax, ecx

.zero:

        ret

endp