1 /* SPDX-License-Identifier: GPL-2.0+ */ 2 /* 3 * Generic bounce buffer implementation 4 * 5 * Copyright (C) 2012 Marek Vasut <marex@denx.de> 6 */ 7 8 #ifndef __INCLUDE_BOUNCEBUF_H__ 9 #define __INCLUDE_BOUNCEBUF_H__ 10 11 #include <linux/types.h> 12 13 /* 14 * GEN_BB_READ -- Data are read from the buffer eg. by DMA hardware. 15 * The source buffer is copied into the bounce buffer (if unaligned, otherwise 16 * the source buffer is used directly) upon start() call, then the operation 17 * requiring the aligned transfer happens, then the bounce buffer is lost upon 18 * stop() call. 19 */ 20 #define GEN_BB_READ (1 << 0) 21 /* 22 * GEN_BB_WRITE -- Data are written into the buffer eg. by DMA hardware. 23 * The source buffer starts in an undefined state upon start() call, then the 24 * operation requiring the aligned transfer happens, then the bounce buffer is 25 * copied into the destination buffer (if unaligned, otherwise destination 26 * buffer is used directly) upon stop() call. 27 */ 28 #define GEN_BB_WRITE (1 << 1) 29 /* 30 * GEN_BB_RW -- Data are read and written into the buffer eg. by DMA hardware. 31 * The source buffer is copied into the bounce buffer (if unaligned, otherwise 32 * the source buffer is used directly) upon start() call, then the operation 33 * requiring the aligned transfer happens, then the bounce buffer is copied 34 * into the destination buffer (if unaligned, otherwise destination buffer is 35 * used directly) upon stop() call. 36 */ 37 #define GEN_BB_RW (GEN_BB_READ | GEN_BB_WRITE) 38 39 struct bounce_buffer { 40 /* Copy of data parameter passed to start() */ 41 void *user_buffer; 42 /* 43 * DMA-aligned buffer. This field is always set to the value that 44 * should be used for DMA; either equal to .user_buffer, or to a 45 * freshly allocated aligned buffer. 46 */ 47 void *bounce_buffer; 48 /* Copy of len parameter passed to start() */ 49 size_t len; 50 /* DMA-aligned buffer length */ 51 size_t len_aligned; 52 /* Copy of flags parameter passed to start() */ 53 unsigned int flags; 54 }; 55 56 /** 57 * bounce_buffer_start() -- Start the bounce buffer session 58 * state: stores state passed between bounce_buffer_{start,stop} 59 * data: pointer to buffer to be aligned 60 * len: length of the buffer 61 * flags: flags describing the transaction, see above. 62 */ 63 int bounce_buffer_start(struct bounce_buffer *state, void *data, 64 size_t len, unsigned int flags); 65 /** 66 * bounce_buffer_stop() -- Finish the bounce buffer session 67 * state: stores state passed between bounce_buffer_{start,stop} 68 */ 69 int bounce_buffer_stop(struct bounce_buffer *state); 70 71 #endif 72