spi_bitbang.h

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#ifndef __SPI_BITBANG_H
#define __SPI_BITBANG_H

#include <linux/workqueue.h>

struct spi_bitbang {
    struct workqueue_struct *workqueue;
    struct work_struct  work;

    spinlock_t      lock;
    struct list_head    queue;
    u8          busy;
    u8          use_dma;
    u8          flags;      /* extra spi->mode support */

    struct spi_master   *master;

    /* setup_transfer() changes clock and/or wordsize to match settings
     * for this transfer; zeroes restore defaults from spi_device.
     */
    int (*setup_transfer)(struct spi_device *spi,
            struct spi_transfer *t);

    void    (*chipselect)(struct spi_device *spi, int is_on);
#define BITBANG_CS_ACTIVE   1   /* normally nCS, active low */
#define BITBANG_CS_INACTIVE 0

    /* txrx_bufs() may handle dma mapping for transfers that don't
     * already have one (transfer.{tx,rx}_dma is zero), or use PIO
     */
    int (*txrx_bufs)(struct spi_device *spi, struct spi_transfer *t);

    /* txrx_word[SPI_MODE_*]() just looks like a shift register */
    u32 (*txrx_word[4])(struct spi_device *spi,
            unsigned nsecs,
            u32 word, u8 bits);
};

/* you can call these default bitbang->master methods from your custom
 * methods, if you like.
 */
extern int spi_bitbang_setup(struct spi_device *spi);
extern void spi_bitbang_cleanup(struct spi_device *spi);
extern int spi_bitbang_transfer(struct spi_device *spi, struct spi_message *m);
extern int spi_bitbang_setup_transfer(struct spi_device *spi,
                      struct spi_transfer *t);

/* start or stop queue processing */
extern int spi_bitbang_start(struct spi_bitbang *spi);
extern int spi_bitbang_stop(struct spi_bitbang *spi);

#endif  /* __SPI_BITBANG_H */