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 */
63struct spi_gpio_platform_data {
64	unsigned	sck;
65	unsigned long	mosi;
66	unsigned long	miso;
67
68	u16		num_chipselect;
69};
70
71#endif /* __LINUX_SPI_GPIO_H */
72