diff options
Diffstat (limited to 'Documentation/spi/spi-summary')
| -rw-r--r-- | Documentation/spi/spi-summary | 25 |
1 files changed, 17 insertions, 8 deletions
diff --git a/Documentation/spi/spi-summary b/Documentation/spi/spi-summary index 76ea6c837be..8861e47e5a2 100644 --- a/Documentation/spi/spi-summary +++ b/Documentation/spi/spi-summary @@ -156,21 +156,29 @@ using the driver model to connect controller and protocol drivers using device tables provided by board specific initialization code. SPI shows up in sysfs in several locations: + /sys/devices/.../CTLR ... physical node for a given SPI controller + /sys/devices/.../CTLR/spiB.C ... spi_device on bus "B", chipselect C, accessed through CTLR. + /sys/bus/spi/devices/spiB.C ... symlink to that physical + .../CTLR/spiB.C device + /sys/devices/.../CTLR/spiB.C/modalias ... identifies the driver that should be used with this device (for hotplug/coldplug) - /sys/bus/spi/devices/spiB.C ... symlink to the physical - spiB.C device - /sys/bus/spi/drivers/D ... driver for one or more spi*.* devices - /sys/class/spi_master/spiB ... class device for the controller - managing bus "B". All the spiB.* devices share the same + /sys/class/spi_master/spiB ... symlink (or actual device node) to + a logical node which could hold class related state for the + controller managing bus "B". All spiB.* devices share one physical SPI bus segment, with SCLK, MOSI, and MISO. +Note that the actual location of the controller's class state depends +on whether you enabled CONFIG_SYSFS_DEPRECATED or not. At this time, +the only class-specific state is the bus number ("B" in "spiB"), so +those /sys/class entries are only useful to quickly identify busses. + How does board-specific init code declare SPI devices? ------------------------------------------------------ @@ -337,7 +345,8 @@ SPI protocol drivers somewhat resemble platform device drivers: The driver core will autmatically attempt to bind this driver to any SPI device whose board_info gave a modalias of "CHIP". Your probe() code -might look like this unless you're creating a class_device: +might look like this unless you're creating a device which is managing +a bus (appearing under /sys/class/spi_master). static int __devinit CHIP_probe(struct spi_device *spi) { @@ -442,7 +451,7 @@ An SPI controller will probably be registered on the platform_bus; write a driver to bind to the device, whichever bus is involved. The main task of this type of driver is to provide an "spi_master". -Use spi_alloc_master() to allocate the master, and class_get_devdata() +Use spi_alloc_master() to allocate the master, and spi_master_get_devdata() to get the driver-private data allocated for that device. struct spi_master *master; @@ -452,7 +461,7 @@ to get the driver-private data allocated for that device. if (!master) return -ENODEV; - c = class_get_devdata(&master->cdev); + c = spi_master_get_devdata(master); The driver will initialize the fields of that spi_master, including the bus number (maybe the same as the platform device ID) and three methods |