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Kernel: Implement a simple Scatter/Gather List
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.
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Kernel/VM/ScatterGatherList.h
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Kernel/VM/ScatterGatherList.h
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/*
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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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#pragma once
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#include <AK/Vector.h>
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#include <Kernel/PhysicalAddress.h>
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#include <Kernel/VM/MemoryManager.h>
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namespace Kernel {
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class ScatterGatherList {
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struct ScatterGatherEntry {
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FlatPtr page_base;
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size_t offset;
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size_t length;
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};
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public:
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static ScatterGatherList create_from_buffer(const u8* buffer, size_t);
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static ScatterGatherList create_from_physical(PhysicalAddress, size_t);
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void add_entry(FlatPtr, size_t offset, size_t size);
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[[nodiscard]] size_t length() const { return m_entries.size(); }
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void for_each_entry(Function<void(const FlatPtr, const size_t)> callback) const;
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private:
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Vector<ScatterGatherEntry> m_entries;
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};
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}
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