89 lines
3.2 KiB
C
89 lines
3.2 KiB
C
/*
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* Generic bounce buffer implementation
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*
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* Copyright (C) 2012 Marek Vasut <marex@denx.de>
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*
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* See file CREDITS for list of people who contributed to this
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* project.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*/
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#ifndef __INCLUDE_BOUNCEBUF_H__
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#define __INCLUDE_BOUNCEBUF_H__
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#include <linux/types.h>
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/*
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* GEN_BB_READ -- Data are read from the buffer eg. by DMA hardware.
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* The source buffer is copied into the bounce buffer (if unaligned, otherwise
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* the source buffer is used directly) upon start() call, then the operation
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* requiring the aligned transfer happens, then the bounce buffer is lost upon
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* stop() call.
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*/
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#define GEN_BB_READ (1 << 0)
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/*
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* GEN_BB_WRITE -- Data are written into the buffer eg. by DMA hardware.
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* The source buffer starts in an undefined state upon start() call, then the
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* operation requiring the aligned transfer happens, then the bounce buffer is
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* copied into the destination buffer (if unaligned, otherwise destination
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* buffer is used directly) upon stop() call.
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*/
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#define GEN_BB_WRITE (1 << 1)
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/*
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* GEN_BB_RW -- Data are read and written into the buffer eg. by DMA hardware.
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* The source buffer is copied into the bounce buffer (if unaligned, otherwise
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* the source buffer is used directly) upon start() call, then the operation
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* requiring the aligned transfer happens, then the bounce buffer is copied
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* into the destination buffer (if unaligned, otherwise destination buffer is
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* used directly) upon stop() call.
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*/
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#define GEN_BB_RW (GEN_BB_READ | GEN_BB_WRITE)
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struct bounce_buffer {
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/* Copy of data parameter passed to start() */
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void *user_buffer;
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/*
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* DMA-aligned buffer. This field is always set to the value that
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* should be used for DMA; either equal to .user_buffer, or to a
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* freshly allocated aligned buffer.
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*/
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void *bounce_buffer;
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/* Copy of len parameter passed to start() */
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size_t len;
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/* DMA-aligned buffer length */
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size_t len_aligned;
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/* Copy of flags parameter passed to start() */
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unsigned int flags;
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};
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/**
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* bounce_buffer_start() -- Start the bounce buffer session
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* state: stores state passed between bounce_buffer_{start,stop}
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* data: pointer to buffer to be aligned
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* len: length of the buffer
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* flags: flags describing the transaction, see above.
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*/
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int bounce_buffer_start(struct bounce_buffer *state, void *data,
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size_t len, unsigned int flags);
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/**
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* bounce_buffer_stop() -- Finish the bounce buffer session
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* state: stores state passed between bounce_buffer_{start,stop}
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*/
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int bounce_buffer_stop(struct bounce_buffer *state);
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#endif
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