epd.c

int spi_write_then_write(struct spi_device *spi,
                        const void *tx_buf_0, unsigned tx_len_0,
                        const void *tx_buf_1, unsigned tx_len_1)
{
        struct spi_message message;
        struct spi_transfer x[2];

        spi_message_init(&message);
        memset(x, 0, sizeof(x));
        if (tx_len_0) {
                x[0].tx_buf = tx_buf_0;
                x[0].len = tx_len_0;
                /* x[0].cs_change = 1; */
                spi_message_add_tail(&x[0], &message);
        }
        if (tx_len_1) {
                x[1].tx_buf = tx_buf_1;
                x[1].len = tx_len_1;
                /* x[1].cs_change = 1; */
                spi_message_add_tail(&x[1], &message);
        }

        return spi_sync(spi, &message);
}

/* int spi_w8w8(struct spi_device *spi, u8 header, u8 data) */
/* { */
/*      return spi_write_then_write(spi, &header, 1, &data, 1); */
/* } */

static inline void SPI(u8 cmd, const u8 *buf, size_t len)
{
        const u8 headers = {0x70, 0x72};

        spi_write_then_write(spi, &headers[0], 1, &cmd, 1);
        spi_write_then_write(spi, &headers[1], 1, buf, len);
}

static inline void SPI_R(u8 cmd, u8 *buf, size_t len)
{
        const u8 headers = {0x70, 0x73};

        spi_write_then_write(spi, &headers[0], 1, &cmd, 1);
        spi_write_then_read(spi, &headers[1], 1, buf, len); // use overread char, set to 0                                                                                                                                                                                       
}

static inline void SPI_RID(u8 cmd, u8 *id)
{
        *id = spi_w8r8(spi, 0x71); // use overread char, set to 0                                                                                                                                                                                                                
}