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