xref: /openbmc/u-boot/include/spi.h (revision e5f00f0180994b7ab218e904b3426f1c66eb6da7)
1  /*
2   * Common SPI Interface: Controller-specific definitions
3   *
4   * (C) Copyright 2001
5   * Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com.
6   *
7   * SPDX-License-Identifier:	GPL-2.0+
8   */
9  
10  #ifndef _SPI_H_
11  #define _SPI_H_
12  
13  /* SPI mode flags */
14  #define SPI_CPHA	BIT(0)			/* clock phase */
15  #define SPI_CPOL	BIT(1)			/* clock polarity */
16  #define SPI_MODE_0	(0|0)			/* (original MicroWire) */
17  #define SPI_MODE_1	(0|SPI_CPHA)
18  #define SPI_MODE_2	(SPI_CPOL|0)
19  #define SPI_MODE_3	(SPI_CPOL|SPI_CPHA)
20  #define SPI_CS_HIGH	BIT(2)			/* CS active high */
21  #define SPI_LSB_FIRST	BIT(3)			/* per-word bits-on-wire */
22  #define SPI_3WIRE	BIT(4)			/* SI/SO signals shared */
23  #define SPI_LOOP	BIT(5)			/* loopback mode */
24  #define SPI_SLAVE	BIT(6)			/* slave mode */
25  #define SPI_PREAMBLE	BIT(7)			/* Skip preamble bytes */
26  #define SPI_TX_BYTE	BIT(8)			/* transmit with 1 wire byte */
27  #define SPI_TX_DUAL	BIT(9)			/* transmit with 2 wires */
28  #define SPI_TX_QUAD	BIT(10)			/* transmit with 4 wires */
29  #define SPI_RX_SLOW	BIT(11)			/* receive with 1 wire slow */
30  #define SPI_RX_DUAL	BIT(12)			/* receive with 2 wires */
31  #define SPI_RX_QUAD	BIT(13)			/* receive with 4 wires */
32  
33  /* Header byte that marks the start of the message */
34  #define SPI_PREAMBLE_END_BYTE	0xec
35  
36  #define SPI_DEFAULT_WORDLEN	8
37  
38  #ifdef CONFIG_DM_SPI
39  /* TODO(sjg@chromium.org): Remove this and use max_hz from struct spi_slave */
40  struct dm_spi_bus {
41  	uint max_hz;
42  };
43  
44  /**
45   * struct dm_spi_platdata - platform data for all SPI slaves
46   *
47   * This describes a SPI slave, a child device of the SPI bus. To obtain this
48   * struct from a spi_slave, use dev_get_parent_platdata(dev) or
49   * dev_get_parent_platdata(slave->dev).
50   *
51   * This data is immuatable. Each time the device is probed, @max_hz and @mode
52   * will be copied to struct spi_slave.
53   *
54   * @cs:		Chip select number (0..n-1)
55   * @max_hz:	Maximum bus speed that this slave can tolerate
56   * @mode:	SPI mode to use for this device (see SPI mode flags)
57   */
58  struct dm_spi_slave_platdata {
59  	unsigned int cs;
60  	uint max_hz;
61  	uint mode;
62  };
63  
64  #endif /* CONFIG_DM_SPI */
65  
66  /**
67   * struct spi_slave - Representation of a SPI slave
68   *
69   * For driver model this is the per-child data used by the SPI bus. It can
70   * be accessed using dev_get_parent_priv() on the slave device. The SPI uclass
71   * sets uip per_child_auto_alloc_size to sizeof(struct spi_slave), and the
72   * driver should not override it. Two platform data fields (max_hz and mode)
73   * are copied into this structure to provide an initial value. This allows
74   * them to be changed, since we should never change platform data in drivers.
75   *
76   * If not using driver model, drivers are expected to extend this with
77   * controller-specific data.
78   *
79   * @dev:		SPI slave device
80   * @max_hz:		Maximum speed for this slave
81   * @speed:		Current bus speed. This is 0 until the bus is first
82   *			claimed.
83   * @bus:		ID of the bus that the slave is attached to. For
84   *			driver model this is the sequence number of the SPI
85   *			bus (bus->seq) so does not need to be stored
86   * @cs:			ID of the chip select connected to the slave.
87   * @mode:		SPI mode to use for this slave (see SPI mode flags)
88   * @wordlen:		Size of SPI word in number of bits
89   * @max_write_size:	If non-zero, the maximum number of bytes which can
90   *			be written at once, excluding command bytes.
91   * @memory_map:		Address of read-only SPI flash access.
92   * @flags:		Indication of SPI flags.
93   */
94  struct spi_slave {
95  #ifdef CONFIG_DM_SPI
96  	struct udevice *dev;	/* struct spi_slave is dev->parentdata */
97  	uint max_hz;
98  	uint speed;
99  #else
100  	unsigned int bus;
101  	unsigned int cs;
102  #endif
103  	uint mode;
104  	unsigned int wordlen;
105  	unsigned int max_write_size;
106  	void *memory_map;
107  	u8 option;
108  
109  	u8 flags;
110  #define SPI_XFER_BEGIN		BIT(0)	/* Assert CS before transfer */
111  #define SPI_XFER_END		BIT(1)	/* Deassert CS after transfer */
112  #define SPI_XFER_ONCE		(SPI_XFER_BEGIN | SPI_XFER_END)
113  #define SPI_XFER_MMAP		BIT(2)	/* Memory Mapped start */
114  #define SPI_XFER_MMAP_END	BIT(3)	/* Memory Mapped End */
115  };
116  
117  /**
118   * Initialization, must be called once on start up.
119   *
120   * TODO: I don't think we really need this.
121   */
122  void spi_init(void);
123  
124  /**
125   * spi_do_alloc_slave - Allocate a new SPI slave (internal)
126   *
127   * Allocate and zero all fields in the spi slave, and set the bus/chip
128   * select. Use the helper macro spi_alloc_slave() to call this.
129   *
130   * @offset:	Offset of struct spi_slave within slave structure.
131   * @size:	Size of slave structure.
132   * @bus:	Bus ID of the slave chip.
133   * @cs:		Chip select ID of the slave chip on the specified bus.
134   */
135  void *spi_do_alloc_slave(int offset, int size, unsigned int bus,
136  			 unsigned int cs);
137  
138  /**
139   * spi_alloc_slave - Allocate a new SPI slave
140   *
141   * Allocate and zero all fields in the spi slave, and set the bus/chip
142   * select.
143   *
144   * @_struct:	Name of structure to allocate (e.g. struct tegra_spi).
145   *		This structure must contain a member 'struct spi_slave *slave'.
146   * @bus:	Bus ID of the slave chip.
147   * @cs:		Chip select ID of the slave chip on the specified bus.
148   */
149  #define spi_alloc_slave(_struct, bus, cs) \
150  	spi_do_alloc_slave(offsetof(_struct, slave), \
151  			    sizeof(_struct), bus, cs)
152  
153  /**
154   * spi_alloc_slave_base - Allocate a new SPI slave with no private data
155   *
156   * Allocate and zero all fields in the spi slave, and set the bus/chip
157   * select.
158   *
159   * @bus:	Bus ID of the slave chip.
160   * @cs:		Chip select ID of the slave chip on the specified bus.
161   */
162  #define spi_alloc_slave_base(bus, cs) \
163  	spi_do_alloc_slave(0, sizeof(struct spi_slave), bus, cs)
164  
165  /**
166   * Set up communications parameters for a SPI slave.
167   *
168   * This must be called once for each slave. Note that this function
169   * usually doesn't touch any actual hardware, it only initializes the
170   * contents of spi_slave so that the hardware can be easily
171   * initialized later.
172   *
173   * @bus:	Bus ID of the slave chip.
174   * @cs:		Chip select ID of the slave chip on the specified bus.
175   * @max_hz:	Maximum SCK rate in Hz.
176   * @mode:	Clock polarity, clock phase and other parameters.
177   *
178   * Returns: A spi_slave reference that can be used in subsequent SPI
179   * calls, or NULL if one or more of the parameters are not supported.
180   */
181  struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
182  		unsigned int max_hz, unsigned int mode);
183  
184  /**
185   * Free any memory associated with a SPI slave.
186   *
187   * @slave:	The SPI slave
188   */
189  void spi_free_slave(struct spi_slave *slave);
190  
191  /**
192   * Claim the bus and prepare it for communication with a given slave.
193   *
194   * This must be called before doing any transfers with a SPI slave. It
195   * will enable and initialize any SPI hardware as necessary, and make
196   * sure that the SCK line is in the correct idle state. It is not
197   * allowed to claim the same bus for several slaves without releasing
198   * the bus in between.
199   *
200   * @slave:	The SPI slave
201   *
202   * Returns: 0 if the bus was claimed successfully, or a negative value
203   * if it wasn't.
204   */
205  int spi_claim_bus(struct spi_slave *slave);
206  
207  /**
208   * Release the SPI bus
209   *
210   * This must be called once for every call to spi_claim_bus() after
211   * all transfers have finished. It may disable any SPI hardware as
212   * appropriate.
213   *
214   * @slave:	The SPI slave
215   */
216  void spi_release_bus(struct spi_slave *slave);
217  
218  /**
219   * Set the word length for SPI transactions
220   *
221   * Set the word length (number of bits per word) for SPI transactions.
222   *
223   * @slave:	The SPI slave
224   * @wordlen:	The number of bits in a word
225   *
226   * Returns: 0 on success, -1 on failure.
227   */
228  int spi_set_wordlen(struct spi_slave *slave, unsigned int wordlen);
229  
230  /**
231   * SPI transfer
232   *
233   * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
234   * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
235   *
236   * The source of the outgoing bits is the "dout" parameter and the
237   * destination of the input bits is the "din" parameter.  Note that "dout"
238   * and "din" can point to the same memory location, in which case the
239   * input data overwrites the output data (since both are buffered by
240   * temporary variables, this is OK).
241   *
242   * spi_xfer() interface:
243   * @slave:	The SPI slave which will be sending/receiving the data.
244   * @bitlen:	How many bits to write and read.
245   * @dout:	Pointer to a string of bits to send out.  The bits are
246   *		held in a byte array and are sent MSB first.
247   * @din:	Pointer to a string of bits that will be filled in.
248   * @flags:	A bitwise combination of SPI_XFER_* flags.
249   *
250   * Returns: 0 on success, not 0 on failure
251   */
252  int  spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
253  		void *din, unsigned long flags);
254  
255  /* Copy memory mapped data */
256  void spi_flash_copy_mmap(void *data, void *offset, size_t len);
257  
258  /**
259   * Determine if a SPI chipselect is valid.
260   * This function is provided by the board if the low-level SPI driver
261   * needs it to determine if a given chipselect is actually valid.
262   *
263   * Returns: 1 if bus:cs identifies a valid chip on this board, 0
264   * otherwise.
265   */
266  int spi_cs_is_valid(unsigned int bus, unsigned int cs);
267  
268  #ifndef CONFIG_DM_SPI
269  /**
270   * Activate a SPI chipselect.
271   * This function is provided by the board code when using a driver
272   * that can't control its chipselects automatically (e.g.
273   * common/soft_spi.c). When called, it should activate the chip select
274   * to the device identified by "slave".
275   */
276  void spi_cs_activate(struct spi_slave *slave);
277  
278  /**
279   * Deactivate a SPI chipselect.
280   * This function is provided by the board code when using a driver
281   * that can't control its chipselects automatically (e.g.
282   * common/soft_spi.c). When called, it should deactivate the chip
283   * select to the device identified by "slave".
284   */
285  void spi_cs_deactivate(struct spi_slave *slave);
286  
287  /**
288   * Set transfer speed.
289   * This sets a new speed to be applied for next spi_xfer().
290   * @slave:	The SPI slave
291   * @hz:		The transfer speed
292   */
293  void spi_set_speed(struct spi_slave *slave, uint hz);
294  #endif
295  
296  /**
297   * Write 8 bits, then read 8 bits.
298   * @slave:	The SPI slave we're communicating with
299   * @byte:	Byte to be written
300   *
301   * Returns: The value that was read, or a negative value on error.
302   *
303   * TODO: This function probably shouldn't be inlined.
304   */
305  static inline int spi_w8r8(struct spi_slave *slave, unsigned char byte)
306  {
307  	unsigned char dout[2];
308  	unsigned char din[2];
309  	int ret;
310  
311  	dout[0] = byte;
312  	dout[1] = 0;
313  
314  	ret = spi_xfer(slave, 16, dout, din, SPI_XFER_BEGIN | SPI_XFER_END);
315  	return ret < 0 ? ret : din[1];
316  }
317  
318  /**
319   * Set up a SPI slave for a particular device tree node
320   *
321   * This calls spi_setup_slave() with the correct bus number. Call
322   * spi_free_slave() to free it later.
323   *
324   * @param blob:		Device tree blob
325   * @param slave_node:	Slave node to use
326   * @param spi_node:	SPI peripheral node to use
327   * @return pointer to new spi_slave structure
328   */
329  struct spi_slave *spi_setup_slave_fdt(const void *blob, int slave_node,
330  				      int spi_node);
331  
332  /**
333   * spi_base_setup_slave_fdt() - helper function to set up a SPI slace
334   *
335   * This decodes SPI properties from the slave node to determine the
336   * chip select and SPI parameters.
337   *
338   * @blob:	Device tree blob
339   * @busnum:	Bus number to use
340   * @node:	Device tree node for the SPI bus
341   */
342  struct spi_slave *spi_base_setup_slave_fdt(const void *blob, int busnum,
343  					   int node);
344  
345  #ifdef CONFIG_DM_SPI
346  
347  /**
348   * struct spi_cs_info - Information about a bus chip select
349   *
350   * @dev:	Connected device, or NULL if none
351   */
352  struct spi_cs_info {
353  	struct udevice *dev;
354  };
355  
356  /**
357   * struct struct dm_spi_ops - Driver model SPI operations
358   *
359   * The uclass interface is implemented by all SPI devices which use
360   * driver model.
361   */
362  struct dm_spi_ops {
363  	/**
364  	 * Claim the bus and prepare it for communication.
365  	 *
366  	 * The device provided is the slave device. It's parent controller
367  	 * will be used to provide the communication.
368  	 *
369  	 * This must be called before doing any transfers with a SPI slave. It
370  	 * will enable and initialize any SPI hardware as necessary, and make
371  	 * sure that the SCK line is in the correct idle state. It is not
372  	 * allowed to claim the same bus for several slaves without releasing
373  	 * the bus in between.
374  	 *
375  	 * @dev:	The SPI slave
376  	 *
377  	 * Returns: 0 if the bus was claimed successfully, or a negative value
378  	 * if it wasn't.
379  	 */
380  	int (*claim_bus)(struct udevice *dev);
381  
382  	/**
383  	 * Release the SPI bus
384  	 *
385  	 * This must be called once for every call to spi_claim_bus() after
386  	 * all transfers have finished. It may disable any SPI hardware as
387  	 * appropriate.
388  	 *
389  	 * @dev:	The SPI slave
390  	 */
391  	int (*release_bus)(struct udevice *dev);
392  
393  	/**
394  	 * Set the word length for SPI transactions
395  	 *
396  	 * Set the word length (number of bits per word) for SPI transactions.
397  	 *
398  	 * @bus:	The SPI slave
399  	 * @wordlen:	The number of bits in a word
400  	 *
401  	 * Returns: 0 on success, -ve on failure.
402  	 */
403  	int (*set_wordlen)(struct udevice *dev, unsigned int wordlen);
404  
405  	/**
406  	 * SPI transfer
407  	 *
408  	 * This writes "bitlen" bits out the SPI MOSI port and simultaneously
409  	 * clocks "bitlen" bits in the SPI MISO port.  That's just the way SPI
410  	 * works.
411  	 *
412  	 * The source of the outgoing bits is the "dout" parameter and the
413  	 * destination of the input bits is the "din" parameter.  Note that
414  	 * "dout" and "din" can point to the same memory location, in which
415  	 * case the input data overwrites the output data (since both are
416  	 * buffered by temporary variables, this is OK).
417  	 *
418  	 * spi_xfer() interface:
419  	 * @dev:	The slave device to communicate with
420  	 * @bitlen:	How many bits to write and read.
421  	 * @dout:	Pointer to a string of bits to send out.  The bits are
422  	 *		held in a byte array and are sent MSB first.
423  	 * @din:	Pointer to a string of bits that will be filled in.
424  	 * @flags:	A bitwise combination of SPI_XFER_* flags.
425  	 *
426  	 * Returns: 0 on success, not -1 on failure
427  	 */
428  	int (*xfer)(struct udevice *dev, unsigned int bitlen, const void *dout,
429  		    void *din, unsigned long flags);
430  
431  	/**
432  	 * Set transfer speed.
433  	 * This sets a new speed to be applied for next spi_xfer().
434  	 * @bus:	The SPI bus
435  	 * @hz:		The transfer speed
436  	 * @return 0 if OK, -ve on error
437  	 */
438  	int (*set_speed)(struct udevice *bus, uint hz);
439  
440  	/**
441  	 * Set the SPI mode/flags
442  	 *
443  	 * It is unclear if we want to set speed and mode together instead
444  	 * of separately.
445  	 *
446  	 * @bus:	The SPI bus
447  	 * @mode:	Requested SPI mode (SPI_... flags)
448  	 * @return 0 if OK, -ve on error
449  	 */
450  	int (*set_mode)(struct udevice *bus, uint mode);
451  
452  	/**
453  	 * Get information on a chip select
454  	 *
455  	 * This is only called when the SPI uclass does not know about a
456  	 * chip select, i.e. it has no attached device. It gives the driver
457  	 * a chance to allow activity on that chip select even so.
458  	 *
459  	 * @bus:	The SPI bus
460  	 * @cs:		The chip select (0..n-1)
461  	 * @info:	Returns information about the chip select, if valid.
462  	 *		On entry info->dev is NULL
463  	 * @return 0 if OK (and @info is set up), -ENODEV if the chip select
464  	 *	   is invalid, other -ve value on error
465  	 */
466  	int (*cs_info)(struct udevice *bus, uint cs, struct spi_cs_info *info);
467  };
468  
469  struct dm_spi_emul_ops {
470  	/**
471  	 * SPI transfer
472  	 *
473  	 * This writes "bitlen" bits out the SPI MOSI port and simultaneously
474  	 * clocks "bitlen" bits in the SPI MISO port.  That's just the way SPI
475  	 * works. Here the device is a slave.
476  	 *
477  	 * The source of the outgoing bits is the "dout" parameter and the
478  	 * destination of the input bits is the "din" parameter.  Note that
479  	 * "dout" and "din" can point to the same memory location, in which
480  	 * case the input data overwrites the output data (since both are
481  	 * buffered by temporary variables, this is OK).
482  	 *
483  	 * spi_xfer() interface:
484  	 * @slave:	The SPI slave which will be sending/receiving the data.
485  	 * @bitlen:	How many bits to write and read.
486  	 * @dout:	Pointer to a string of bits sent to the device. The
487  	 *		bits are held in a byte array and are sent MSB first.
488  	 * @din:	Pointer to a string of bits that will be sent back to
489  	 *		the master.
490  	 * @flags:	A bitwise combination of SPI_XFER_* flags.
491  	 *
492  	 * Returns: 0 on success, not -1 on failure
493  	 */
494  	int (*xfer)(struct udevice *slave, unsigned int bitlen,
495  		    const void *dout, void *din, unsigned long flags);
496  };
497  
498  /**
499   * spi_find_bus_and_cs() - Find bus and slave devices by number
500   *
501   * Given a bus number and chip select, this finds the corresponding bus
502   * device and slave device. Neither device is activated by this function,
503   * although they may have been activated previously.
504   *
505   * @busnum:	SPI bus number
506   * @cs:		Chip select to look for
507   * @busp:	Returns bus device
508   * @devp:	Return slave device
509   * @return 0 if found, -ENODEV on error
510   */
511  int spi_find_bus_and_cs(int busnum, int cs, struct udevice **busp,
512  			struct udevice **devp);
513  
514  /**
515   * spi_get_bus_and_cs() - Find and activate bus and slave devices by number
516   *
517   * Given a bus number and chip select, this finds the corresponding bus
518   * device and slave device.
519   *
520   * If no such slave exists, and drv_name is not NULL, then a new slave device
521   * is automatically bound on this chip select.
522   *
523   * Ths new slave device is probed ready for use with the given speed and mode.
524   *
525   * @busnum:	SPI bus number
526   * @cs:		Chip select to look for
527   * @speed:	SPI speed to use for this slave
528   * @mode:	SPI mode to use for this slave
529   * @drv_name:	Name of driver to attach to this chip select
530   * @dev_name:	Name of the new device thus created
531   * @busp:	Returns bus device
532   * @devp:	Return slave device
533   * @return 0 if found, -ve on error
534   */
535  int spi_get_bus_and_cs(int busnum, int cs, int speed, int mode,
536  			const char *drv_name, const char *dev_name,
537  			struct udevice **busp, struct spi_slave **devp);
538  
539  /**
540   * spi_chip_select() - Get the chip select for a slave
541   *
542   * @return the chip select this slave is attached to
543   */
544  int spi_chip_select(struct udevice *slave);
545  
546  /**
547   * spi_find_chip_select() - Find the slave attached to chip select
548   *
549   * @bus:	SPI bus to search
550   * @cs:		Chip select to look for
551   * @devp:	Returns the slave device if found
552   * @return 0 if found, -ENODEV on error
553   */
554  int spi_find_chip_select(struct udevice *bus, int cs, struct udevice **devp);
555  
556  /**
557   * spi_slave_ofdata_to_platdata() - decode standard SPI platform data
558   *
559   * This decodes the speed and mode for a slave from a device tree node
560   *
561   * @blob:	Device tree blob
562   * @node:	Node offset to read from
563   * @plat:	Place to put the decoded information
564   */
565  int spi_slave_ofdata_to_platdata(struct udevice *dev,
566  				 struct dm_spi_slave_platdata *plat);
567  
568  /**
569   * spi_cs_info() - Check information on a chip select
570   *
571   * This checks a particular chip select on a bus to see if it has a device
572   * attached, or is even valid.
573   *
574   * @bus:	The SPI bus
575   * @cs:		The chip select (0..n-1)
576   * @info:	Returns information about the chip select, if valid
577   * @return 0 if OK (and @info is set up), -ENODEV if the chip select
578   *	   is invalid, other -ve value on error
579   */
580  int spi_cs_info(struct udevice *bus, uint cs, struct spi_cs_info *info);
581  
582  struct sandbox_state;
583  
584  /**
585   * sandbox_spi_get_emul() - get an emulator for a SPI slave
586   *
587   * This provides a way to attach an emulated SPI device to a particular SPI
588   * slave, so that xfer() operations on the slave will be handled by the
589   * emulator. If a emulator already exists on that chip select it is returned.
590   * Otherwise one is created.
591   *
592   * @state:	Sandbox state
593   * @bus:	SPI bus requesting the emulator
594   * @slave:	SPI slave device requesting the emulator
595   * @emuip:	Returns pointer to emulator
596   * @return 0 if OK, -ve on error
597   */
598  int sandbox_spi_get_emul(struct sandbox_state *state,
599  			 struct udevice *bus, struct udevice *slave,
600  			 struct udevice **emulp);
601  
602  /**
603   * Claim the bus and prepare it for communication with a given slave.
604   *
605   * This must be called before doing any transfers with a SPI slave. It
606   * will enable and initialize any SPI hardware as necessary, and make
607   * sure that the SCK line is in the correct idle state. It is not
608   * allowed to claim the same bus for several slaves without releasing
609   * the bus in between.
610   *
611   * @dev:	The SPI slave device
612   *
613   * Returns: 0 if the bus was claimed successfully, or a negative value
614   * if it wasn't.
615   */
616  int dm_spi_claim_bus(struct udevice *dev);
617  
618  /**
619   * Release the SPI bus
620   *
621   * This must be called once for every call to dm_spi_claim_bus() after
622   * all transfers have finished. It may disable any SPI hardware as
623   * appropriate.
624   *
625   * @slave:	The SPI slave device
626   */
627  void dm_spi_release_bus(struct udevice *dev);
628  
629  /**
630   * SPI transfer
631   *
632   * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
633   * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
634   *
635   * The source of the outgoing bits is the "dout" parameter and the
636   * destination of the input bits is the "din" parameter.  Note that "dout"
637   * and "din" can point to the same memory location, in which case the
638   * input data overwrites the output data (since both are buffered by
639   * temporary variables, this is OK).
640   *
641   * dm_spi_xfer() interface:
642   * @dev:	The SPI slave device which will be sending/receiving the data.
643   * @bitlen:	How many bits to write and read.
644   * @dout:	Pointer to a string of bits to send out.  The bits are
645   *		held in a byte array and are sent MSB first.
646   * @din:	Pointer to a string of bits that will be filled in.
647   * @flags:	A bitwise combination of SPI_XFER_* flags.
648   *
649   * Returns: 0 on success, not 0 on failure
650   */
651  int dm_spi_xfer(struct udevice *dev, unsigned int bitlen,
652  		const void *dout, void *din, unsigned long flags);
653  
654  /* Access the operations for a SPI device */
655  #define spi_get_ops(dev)	((struct dm_spi_ops *)(dev)->driver->ops)
656  #define spi_emul_get_ops(dev)	((struct dm_spi_emul_ops *)(dev)->driver->ops)
657  #endif /* CONFIG_DM_SPI */
658  
659  #endif	/* _SPI_H_ */
660