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Kernel: Implement a simple Scatter/Gather List

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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.
This commit is contained in:
Idan Horowitz 2021-01-20 18:34:16 +02:00 • committed by Andreas Kling
parent ecfa7cb824
commit acdd1424bc
4 changed files with 124 additions and 0 deletions
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Kernel/VM/ScatterGatherList.h Normal file
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/*
* Copyright (c) 2021, the SerenityOS developers.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <AK/Vector.h>
#include <Kernel/PhysicalAddress.h>
#include <Kernel/VM/MemoryManager.h>
namespace Kernel {
class ScatterGatherList {
struct ScatterGatherEntry {
FlatPtr page_base;
size_t offset;
size_t length;
};
public:
static ScatterGatherList create_from_buffer(const u8* buffer, size_t);
static ScatterGatherList create_from_physical(PhysicalAddress, size_t);
void add_entry(FlatPtr, size_t offset, size_t size);
[[nodiscard]] size_t length() const { return m_entries.size(); }
void for_each_entry(Function<void(const FlatPtr, const size_t)> callback) const;
private:
Vector<ScatterGatherEntry> m_entries;
};
}