1 /* 2 * Generic bounce buffer implementation 3 * 4 * Copyright (C) 2012 Marek Vasut <marex@denx.de> 5 * 6 * SPDX-License-Identifier: GPL-2.0+ 7 */ 8 9 #ifndef __INCLUDE_BOUNCEBUF_H__ 10 #define __INCLUDE_BOUNCEBUF_H__ 11 12 #include <linux/types.h> 13 14 /* 15 * GEN_BB_READ -- Data are read from the buffer eg. by DMA hardware. 16 * The source buffer is copied into the bounce buffer (if unaligned, otherwise 17 * the source buffer is used directly) upon start() call, then the operation 18 * requiring the aligned transfer happens, then the bounce buffer is lost upon 19 * stop() call. 20 */ 21 #define GEN_BB_READ (1 << 0) 22 /* 23 * GEN_BB_WRITE -- Data are written into the buffer eg. by DMA hardware. 24 * The source buffer starts in an undefined state upon start() call, then the 25 * operation requiring the aligned transfer happens, then the bounce buffer is 26 * copied into the destination buffer (if unaligned, otherwise destination 27 * buffer is used directly) upon stop() call. 28 */ 29 #define GEN_BB_WRITE (1 << 1) 30 /* 31 * GEN_BB_RW -- Data are read and written into the buffer eg. by DMA hardware. 32 * The source buffer is copied into the bounce buffer (if unaligned, otherwise 33 * the source buffer is used directly) upon start() call, then the operation 34 * requiring the aligned transfer happens, then the bounce buffer is copied 35 * into the destination buffer (if unaligned, otherwise destination buffer is 36 * used directly) upon stop() call. 37 */ 38 #define GEN_BB_RW (GEN_BB_READ | GEN_BB_WRITE) 39 40 struct bounce_buffer { 41 /* Copy of data parameter passed to start() */ 42 void *user_buffer; 43 /* 44 * DMA-aligned buffer. This field is always set to the value that 45 * should be used for DMA; either equal to .user_buffer, or to a 46 * freshly allocated aligned buffer. 47 */ 48 void *bounce_buffer; 49 /* Copy of len parameter passed to start() */ 50 size_t len; 51 /* DMA-aligned buffer length */ 52 size_t len_aligned; 53 /* Copy of flags parameter passed to start() */ 54 unsigned int flags; 55 }; 56 57 /** 58 * bounce_buffer_start() -- Start the bounce buffer session 59 * state: stores state passed between bounce_buffer_{start,stop} 60 * data: pointer to buffer to be aligned 61 * len: length of the buffer 62 * flags: flags describing the transaction, see above. 63 */ 64 int bounce_buffer_start(struct bounce_buffer *state, void *data, 65 size_t len, unsigned int flags); 66 /** 67 * bounce_buffer_stop() -- Finish the bounce buffer session 68 * state: stores state passed between bounce_buffer_{start,stop} 69 */ 70 int bounce_buffer_stop(struct bounce_buffer *state); 71 72 #endif 73