driver-api/driver-model/platform.rst

6 platform bus:  platform_device, and platform_driver.  This pseudo-bus
8 like those used to integrate peripherals on many system-on-chip
16 entities in the system. This includes legacy port-based devices and
18 into system-on-chip platforms.  What they usually have in common
28 	u32		id;
61 Or, in common situations where the device is known not to be hot-pluggable,
85 As a rule, platform specific (and often board-specific) setup code will
101 a kernel for a specific target board.  Such board-specific kernels are
112 calls to clk_get(&pdev->dev, clock_name) return them as needed.
118 on a non-driver role:  the driver registers its platform device, rather than
124 original IBM PCs, rely on error-prone "probe-the-hardware" models for hardware
126 bus-level support for dynamic configuration (PCI, USB), or device tables
138 using these calls except with such hotplug-deficient drivers::
141 			const char *name, int id);
148 			const char *name, int id,
151 You can use platform_device_register_simple() as a one-step call to allocate
162     * platform_device.id ... the device instance number, or else "-1"
165 These are concatenated, so name/id "serial"/0 indicates bus_id "serial.0", and
166 "serial/3" indicates bus_id "serial.3"; both would use the platform_driver
167 named "serial".  While "my_rtc"/-1 would be bus_id "my_rtc" (no instance id)
175     - Whenever a device is registered, the drivers for that bus are
179     - When a driver is registered using platform_driver_register(), all
183     - Registering a driver using platform_driver_probe() works just like
186       this interface is only for use with non-hotpluggable devices.)
195 Example: "earlyprintk" class early serial console in 6 steps
200 early_platform_add_devices(). In the case of early serial console this
201 should be hardware configuration for the serial port. Devices registered
209 For the early serial console case the user can specify port on the
210 kernel command line as "earlyprintk=serial.0" where "earlyprintk" is
211 the class string, "serial" is the name of the platform driver and
212 0 is the platform device id. If the id is -1 then the dot and the
213 id can be omitted.
220 step 2 have priority over these. This step is omitted by the serial
221 driver example since the early serial driver code should be disabled
226 Compiled-in platform drivers making use of early_platform_init() are
227 automatically registered during step 2 or 3. The serial driver example
236 as possible may be good for the serial port case.
244 time. The early serial driver performs register_console() at this point.