1 #ifndef __LINUX_SPI_GPIO_H
2 #define __LINUX_SPI_GPIO_H
3 
4 /*
5  * For each bitbanged SPI bus, set up a platform_device node with:
6  *   - name "spi_gpio"
7  *   - id the same as the SPI bus number it implements
8  *   - dev.platform data pointing to a struct spi_gpio_platform_data
9  *
10  * Or, see the driver code for information about speedups that are
11  * possible on platforms that support inlined access for GPIOs (no
12  * spi_gpio_platform_data is used).
13  *
14  * Use spi_board_info with these busses in the usual way, being sure
15  * that the controller_data being the GPIO used for each device's
16  * chipselect:
17  *
18  *	static struct spi_board_info ... [] = {
19  *	...
20  *		// this slave uses GPIO 42 for its chipselect
21  *		.controller_data = (void *) 42,
22  *	...
23  *		// this one uses GPIO 86 for its chipselect
24  *		.controller_data = (void *) 86,
25  *	...
26  *	};
27  *
28  * If chipselect is not used (there's only one device on the bus), assign
29  * SPI_GPIO_NO_CHIPSELECT to the controller_data:
30  *		.controller_data = (void *) SPI_GPIO_NO_CHIPSELECT;
31  *
32  * If the MISO or MOSI pin is not available then it should be set to
33  * SPI_GPIO_NO_MISO or SPI_GPIO_NO_MOSI.
34  *
35  * If the bitbanged bus is later switched to a "native" controller,
36  * that platform_device and controller_data should be removed.
37  */
38 
39 #define SPI_GPIO_NO_CHIPSELECT		((unsigned long)-1l)
40 #define SPI_GPIO_NO_MISO		((unsigned long)-1l)
41 #define SPI_GPIO_NO_MOSI		((unsigned long)-1l)
42 
43 /**
44  * struct spi_gpio_platform_data - parameter for bitbanged SPI master
45  * @sck: number of the GPIO used for clock output
46  * @mosi: number of the GPIO used for Master Output, Slave In (MOSI) data
47  * @miso: number of the GPIO used for Master Input, Slave Output (MISO) data
48  * @num_chipselect: how many slaves to allow
49  *
50  * All GPIO signals used with the SPI bus managed through this driver
51  * (chipselects, MOSI, MISO, SCK) must be configured as GPIOs, instead
52  * of some alternate function.
53  *
54  * It can be convenient to use this driver with pins that have alternate
55  * functions associated with a "native" SPI controller if a driver for that
56  * controller is not available, or is missing important functionality.
57  *
58  * On platforms which can do so, configure MISO with a weak pullup unless
59  * there's an external pullup on that signal.  That saves power by avoiding
60  * floating signals.  (A weak pulldown would save power too, but many
61  * drivers expect to see all-ones data as the no slave "response".)
62  */
63 struct spi_gpio_platform_data {
64 	unsigned	sck;
65 	unsigned	mosi;
66 	unsigned	miso;
67 
68 	u16		num_chipselect;
69 };
70 
71 #endif /* __LINUX_SPI_GPIO_H */
72