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;
62 Or, in common situations where the device is known not to be hot-pluggable,
86 As a rule, platform specific (and often board-specific) setup code will
102 a kernel for a specific target board.  Such board-specific kernels are
113 calls to clk_get(&pdev->dev, clock_name) return them as needed.
119 on a non-driver role:  the driver registers its platform device, rather than
125 original IBM PCs, rely on error-prone "probe-the-hardware" models for hardware
127 bus-level support for dynamic configuration (PCI, USB), or device tables
139 using these calls except with such hotplug-deficient drivers::
142 			const char *name, int id);
149 			const char *name, int id,
152 You can use platform_device_register_simple() as a one-step call to allocate
163     * platform_device.id ... the device instance number, or else "-1"
166 These are concatenated, so name/id "serial"/0 indicates bus_id "serial.0", and
167 "serial/3" indicates bus_id "serial.3"; both would use the platform_driver
168 named "serial".  While "my_rtc"/-1 would be bus_id "my_rtc" (no instance id)
176     - Whenever a device is registered, the drivers for that bus are
180     - When a driver is registered using platform_driver_register(), all
184     - Registering a driver using platform_driver_probe() works just like
187       this interface is only for use with non-hotpluggable devices.)
196 Example: "earlyprintk" class early serial console in 6 steps
201 early_platform_add_devices(). In the case of early serial console this
202 should be hardware configuration for the serial port. Devices registered
210 For the early serial console case the user can specify port on the
211 kernel command line as "earlyprintk=serial.0" where "earlyprintk" is
212 the class string, "serial" is the name of the platform driver and
213 0 is the platform device id. If the id is -1 then the dot and the
214 id can be omitted.
221 step 2 have priority over these. This step is omitted by the serial
222 driver example since the early serial driver code should be disabled
227 Compiled-in platform drivers making use of early_platform_init() are
228 automatically registered during step 2 or 3. The serial driver example
237 as possible may be good for the serial port case.
245 time. The early serial driver performs register_console() at this point.