1SPI_WRITE_THEN_READ(9)  Serial Peripheral Interface (S  SPI_WRITE_THEN_READ(9)
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NAME

6       spi_write_then_read - SPI synchronous write followed by read
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SYNOPSIS

9       int spi_write_then_read(struct spi_device * spi, const u8 * txbuf,
10                               unsigned n_tx, u8 * rxbuf, unsigned n_rx);
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ARGUMENTS

13       spi
14           device with which data will be exchanged
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16       txbuf
17           data to be written (need not be dma-safe)
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19       n_tx
20           size of txbuf, in bytes
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22       rxbuf
23           buffer into which data will be read (need not be dma-safe)
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25       n_rx
26           size of rxbuf, in bytes
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CONTEXT

29       can sleep
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DESCRIPTION

32       This performs a half duplex MicroWire style transaction with the
33       device, sending txbuf and then reading rxbuf. The return value is zero
34       for success, else a negative errno status code. This call may only be
35       used from a context that may sleep.
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37       Parameters to this routine are always copied using a small buffer;
38       portable code should never use this for more than 32 bytes.
39       Performance-sensitive or bulk transfer code should instead use
40       spi_{async,sync}() calls with dma-safe buffers.
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43Kernel Hackers Manual 2.6.       November 2011          SPI_WRITE_THEN_READ(9)
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