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acdd1424bc
This allows converting a single virtual buffer into its non-physically contiguous parts, this is especially useful for DMA-based devices that support scatter/gather-like functionality, as it eliminates the need to clone outgoing buffers into one physically contiguous buffer.
68 lines
2.7 KiB
C++
68 lines
2.7 KiB
C++
/*
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* Copyright (c) 2021, the SerenityOS developers.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <Kernel/VM/ScatterGatherList.h>
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namespace Kernel {
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ScatterGatherList ScatterGatherList::create_from_buffer(const u8* buffer, size_t size)
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{
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VERIFY(buffer && size);
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ScatterGatherList new_list;
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auto* region = MM.find_region_from_vaddr(VirtualAddress(buffer));
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VERIFY(region);
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while (size > 0) {
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size_t offset_in_page = (VirtualAddress(buffer) - region->vaddr()).get() % PAGE_SIZE;
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size_t size_in_page = min(PAGE_SIZE - offset_in_page, size);
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VERIFY(offset_in_page + size_in_page - 1 <= PAGE_SIZE);
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new_list.add_entry(region->physical_page(region->page_index_from_address(VirtualAddress(buffer)))->paddr().get(), offset_in_page, size_in_page);
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size -= size_in_page;
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buffer += size_in_page;
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}
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return new_list;
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}
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ScatterGatherList ScatterGatherList::create_from_physical(PhysicalAddress paddr, size_t size)
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{
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VERIFY(!paddr.is_null() && size);
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ScatterGatherList new_list;
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new_list.add_entry(paddr.page_base().get(), paddr.offset_in_page(), size);
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return new_list;
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}
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void ScatterGatherList::add_entry(FlatPtr addr, size_t offset, size_t size)
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{
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m_entries.append({ addr, offset, size });
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}
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void ScatterGatherList::for_each_entry(Function<void(const FlatPtr, const size_t)> callback) const
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{
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for (auto& entry : m_entries)
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callback(entry.page_base + entry.offset, entry.length);
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}
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}
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