tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 the bitbanged bus is later switched to a "native" controller,
29 * that platform_device and controller_data should be removed.
30 */
31
32/**
33 * struct spi_gpio_platform_data - parameter for bitbanged SPI master
34 * @sck: number of the GPIO used for clock output
35 * @mosi: number of the GPIO used for Master Output, Slave In (MOSI) data
36 * @miso: number of the GPIO used for Master Input, Slave Output (MISO) data
37 * @num_chipselect: how many slaves to allow
38 *
39 * All GPIO signals used with the SPI bus managed through this driver
40 * (chipselects, MOSI, MISO, SCK) must be configured as GPIOs, instead
41 * of some alternate function.
42 *
43 * It can be convenient to use this driver with pins that have alternate
44 * functions associated with a "native" SPI controller if a driver for that
45 * controller is not available, or is missing important functionality.
46 *
47 * On platforms which can do so, configure MISO with a weak pullup unless
48 * there's an external pullup on that signal. That saves power by avoiding
49 * floating signals. (A weak pulldown would save power too, but many
50 * drivers expect to see all-ones data as the no slave "response".)
51 */
52struct spi_gpio_platform_data {
53 unsigned sck;
54 unsigned mosi;
55 unsigned miso;
56
57 u16 num_chipselect;
58};
59
60#endif /* __LINUX_SPI_GPIO_H */