LXR linux/include/linux/spi/spi

   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 bitbanged bus is later switched to a "native" controller,
  33 * that platform_device and controller_data should be removed.
  34 */
  35
  36#define SPI_GPIO_NO_CHIPSELECT          ((unsigned long)-1l)
  37
  38/**
  39 * struct spi_gpio_platform_data - parameter for bitbanged SPI master
  40 * @sck: number of the GPIO used for clock output
  41 * @mosi: number of the GPIO used for Master Output, Slave In (MOSI) data
  42 * @miso: number of the GPIO used for Master Input, Slave Output (MISO) data
  43 * @num_chipselect: how many slaves to allow
  44 *
  45 * All GPIO signals used with the SPI bus managed through this driver
  46 * (chipselects, MOSI, MISO, SCK) must be configured as GPIOs, instead
  47 * of some alternate function.
  48 *
  49 * It can be convenient to use this driver with pins that have alternate
  50 * functions associated with a "native" SPI controller if a driver for that
  51 * controller is not available, or is missing important functionality.
  52 *
  53 * On platforms which can do so, configure MISO with a weak pullup unless
  54 * there's an external pullup on that signal.  That saves power by avoiding
  55 * floating signals.  (A weak pulldown would save power too, but many
  56 * drivers expect to see all-ones data as the no slave "response".)
  57 */
  58struct spi_gpio_platform_data {
  59        unsigned        sck;
  60        unsigned        mosi;
  61        unsigned        miso;
  62
  63        u16             num_chipselect;
  64};
  65
  66#endif /* __LINUX_SPI_GPIO_H */
  67