be probed later if another device registers. (Which is OK, since
this interface is only for use with non-hotpluggable devices.)
+
+Early Platform Devices and Drivers
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The early platform interfaces provide platform data to platform device
+drivers early on during the system boot. The code is built on top of the
+early_param() command line parsing and can be executed very early on.
+
+Example: "earlyprintk" class early serial console in 6 steps
+
+1. Registering early platform device data
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The architecture code registers platform device data using the function
+early_platform_add_devices(). In the case of early serial console this
+should be hardware configuration for the serial port. Devices registered
+at this point will later on be matched against early platform drivers.
+
+2. Parsing kernel command line
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The architecture code calls parse_early_param() to parse the kernel
+command line. This will execute all matching early_param() callbacks.
+User specified early platform devices will be registered at this point.
+For the early serial console case the user can specify port on the
+kernel command line as "earlyprintk=serial.0" where "earlyprintk" is
+the class string, "serial" is the name of the platfrom driver and
+0 is the platform device id. If the id is -1 then the dot and the
+id can be omitted.
+
+3. Installing early platform drivers belonging to a certain class
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The architecture code may optionally force registration of all early
+platform drivers belonging to a certain class using the function
+early_platform_driver_register_all(). User specified devices from
+step 2 have priority over these. This step is omitted by the serial
+driver example since the early serial driver code should be disabled
+unless the user has specified port on the kernel command line.
+
+4. Early platform driver registration
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Compiled-in platform drivers making use of early_platform_init() are
+automatically registered during step 2 or 3. The serial driver example
+should use early_platform_init("earlyprintk", &platform_driver).
+
+5. Probing of early platform drivers belonging to a certain class
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The architecture code calls early_platform_driver_probe() to match
+registered early platform devices associated with a certain class with
+registered early platform drivers. Matched devices will get probed().
+This step can be executed at any point during the early boot. As soon
+as possible may be good for the serial port case.
+
+6. Inside the early platform driver probe()
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The driver code needs to take special care during early boot, especially
+when it comes to memory allocation and interrupt registration. The code
+in the probe() function can use is_early_platform_device() to check if
+it is called at early platform device or at the regular platform device
+time. The early serial driver performs register_console() at this point.
+
+For further information, see <linux/platform_device.h>.
{
int error;
+ early_platform_cleanup();
+
error = device_register(&platform_bus);
if (error)
return error;
}
EXPORT_SYMBOL_GPL(dma_get_required_mask);
#endif
+
+static __initdata LIST_HEAD(early_platform_driver_list);
+static __initdata LIST_HEAD(early_platform_device_list);
+
+/**
+ * early_platform_driver_register
+ * @edrv: early_platform driver structure
+ * @buf: string passed from early_param()
+ */
+int __init early_platform_driver_register(struct early_platform_driver *epdrv,
+ char *buf)
+{
+ unsigned long index;
+ int n;
+
+ /* Simply add the driver to the end of the global list.
+ * Drivers will by default be put on the list in compiled-in order.
+ */
+ if (!epdrv->list.next) {
+ INIT_LIST_HEAD(&epdrv->list);
+ list_add_tail(&epdrv->list, &early_platform_driver_list);
+ }
+
+ /* If the user has specified device then make sure the driver
+ * gets prioritized. The driver of the last device specified on
+ * command line will be put first on the list.
+ */
+ n = strlen(epdrv->pdrv->driver.name);
+ if (buf && !strncmp(buf, epdrv->pdrv->driver.name, n)) {
+ list_move(&epdrv->list, &early_platform_driver_list);
+
+ if (!strcmp(buf, epdrv->pdrv->driver.name))
+ epdrv->requested_id = -1;
+ else if (buf[n] == '.' && strict_strtoul(&buf[n + 1], 10,
+ &index) == 0)
+ epdrv->requested_id = index;
+ else
+ epdrv->requested_id = EARLY_PLATFORM_ID_ERROR;
+ }
+
+ return 0;
+}
+
+/**
+ * early_platform_add_devices - add a numbers of early platform devices
+ * @devs: array of early platform devices to add
+ * @num: number of early platform devices in array
+ */
+void __init early_platform_add_devices(struct platform_device **devs, int num)
+{
+ struct device *dev;
+ int i;
+
+ /* simply add the devices to list */
+ for (i = 0; i < num; i++) {
+ dev = &devs[i]->dev;
+
+ if (!dev->devres_head.next) {
+ INIT_LIST_HEAD(&dev->devres_head);
+ list_add_tail(&dev->devres_head,
+ &early_platform_device_list);
+ }
+ }
+}
+
+/**
+ * early_platform_driver_register_all
+ * @class_str: string to identify early platform driver class
+ */
+void __init early_platform_driver_register_all(char *class_str)
+{
+ /* The "class_str" parameter may or may not be present on the kernel
+ * command line. If it is present then there may be more than one
+ * matching parameter.
+ *
+ * Since we register our early platform drivers using early_param()
+ * we need to make sure that they also get registered in the case
+ * when the parameter is missing from the kernel command line.
+ *
+ * We use parse_early_options() to make sure the early_param() gets
+ * called at least once. The early_param() may be called more than
+ * once since the name of the preferred device may be specified on
+ * the kernel command line. early_platform_driver_register() handles
+ * this case for us.
+ */
+ parse_early_options(class_str);
+}
+
+/**
+ * early_platform_match
+ * @edrv: early platform driver structure
+ * @id: id to match against
+ */
+static __init struct platform_device *
+early_platform_match(struct early_platform_driver *epdrv, int id)
+{
+ struct platform_device *pd;
+
+ list_for_each_entry(pd, &early_platform_device_list, dev.devres_head)
+ if (platform_match(&pd->dev, &epdrv->pdrv->driver))
+ if (pd->id == id)
+ return pd;
+
+ return NULL;
+}
+
+/**
+ * early_platform_left
+ * @edrv: early platform driver structure
+ * @id: return true if id or above exists
+ */
+static __init int early_platform_left(struct early_platform_driver *epdrv,
+ int id)
+{
+ struct platform_device *pd;
+
+ list_for_each_entry(pd, &early_platform_device_list, dev.devres_head)
+ if (platform_match(&pd->dev, &epdrv->pdrv->driver))
+ if (pd->id >= id)
+ return 1;
+
+ return 0;
+}
+
+/**
+ * early_platform_driver_probe_id
+ * @class_str: string to identify early platform driver class
+ * @id: id to match against
+ * @nr_probe: number of platform devices to successfully probe before exiting
+ */
+static int __init early_platform_driver_probe_id(char *class_str,
+ int id,
+ int nr_probe)
+{
+ struct early_platform_driver *epdrv;
+ struct platform_device *match;
+ int match_id;
+ int n = 0;
+ int left = 0;
+
+ list_for_each_entry(epdrv, &early_platform_driver_list, list) {
+ /* only use drivers matching our class_str */
+ if (strcmp(class_str, epdrv->class_str))
+ continue;
+
+ if (id == -2) {
+ match_id = epdrv->requested_id;
+ left = 1;
+
+ } else {
+ match_id = id;
+ left += early_platform_left(epdrv, id);
+
+ /* skip requested id */
+ switch (epdrv->requested_id) {
+ case EARLY_PLATFORM_ID_ERROR:
+ case EARLY_PLATFORM_ID_UNSET:
+ break;
+ default:
+ if (epdrv->requested_id == id)
+ match_id = EARLY_PLATFORM_ID_UNSET;
+ }
+ }
+
+ switch (match_id) {
+ case EARLY_PLATFORM_ID_ERROR:
+ pr_warning("%s: unable to parse %s parameter\n",
+ class_str, epdrv->pdrv->driver.name);
+ /* fall-through */
+ case EARLY_PLATFORM_ID_UNSET:
+ match = NULL;
+ break;
+ default:
+ match = early_platform_match(epdrv, match_id);
+ }
+
+ if (match) {
+ if (epdrv->pdrv->probe(match))
+ pr_warning("%s: unable to probe %s early.\n",
+ class_str, match->name);
+ else
+ n++;
+ }
+
+ if (n >= nr_probe)
+ break;
+ }
+
+ if (left)
+ return n;
+ else
+ return -ENODEV;
+}
+
+/**
+ * early_platform_driver_probe
+ * @class_str: string to identify early platform driver class
+ * @nr_probe: number of platform devices to successfully probe before exiting
+ * @user_only: only probe user specified early platform devices
+ */
+int __init early_platform_driver_probe(char *class_str,
+ int nr_probe,
+ int user_only)
+{
+ int k, n, i;
+
+ n = 0;
+ for (i = -2; n < nr_probe; i++) {
+ k = early_platform_driver_probe_id(class_str, i, nr_probe - n);
+
+ if (k < 0)
+ break;
+
+ n += k;
+
+ if (user_only)
+ break;
+ }
+
+ return n;
+}
+
+/**
+ * early_platform_cleanup - clean up early platform code
+ */
+void __init early_platform_cleanup(void)
+{
+ struct platform_device *pd, *pd2;
+
+ /* clean up the devres list used to chain devices */
+ list_for_each_entry_safe(pd, pd2, &early_platform_device_list,
+ dev.devres_head) {
+ list_del(&pd->dev.devres_head);
+ memset(&pd->dev.devres_head, 0, sizeof(pd->dev.devres_head));
+ }
+}
+
#define platform_get_drvdata(_dev) dev_get_drvdata(&(_dev)->dev)
#define platform_set_drvdata(_dev,data) dev_set_drvdata(&(_dev)->dev, (data))
+/* early platform driver interface */
+struct early_platform_driver {
+ const char *class_str;
+ struct platform_driver *pdrv;
+ struct list_head list;
+ int requested_id;
+};
+
+#define EARLY_PLATFORM_ID_UNSET -2
+#define EARLY_PLATFORM_ID_ERROR -3
+
+extern int early_platform_driver_register(struct early_platform_driver *epdrv,
+ char *buf);
+extern void early_platform_add_devices(struct platform_device **devs, int num);
+
+static inline int is_early_platform_device(struct platform_device *pdev)
+{
+ return !pdev->dev.driver;
+}
+
+extern void early_platform_driver_register_all(char *class_str);
+extern int early_platform_driver_probe(char *class_str,
+ int nr_probe, int user_only);
+extern void early_platform_cleanup(void);
+
+
+#ifndef MODULE
+#define early_platform_init(class_string, platform_driver) \
+static __initdata struct early_platform_driver early_driver = { \
+ .class_str = class_string, \
+ .pdrv = platform_driver, \
+ .requested_id = EARLY_PLATFORM_ID_UNSET, \
+}; \
+static int __init early_platform_driver_setup_func(char *buf) \
+{ \
+ return early_platform_driver_register(&early_driver, buf); \
+} \
+early_param(class_string, early_platform_driver_setup_func)
+#else /* MODULE */
+#define early_platform_init(class_string, platform_driver)
+#endif /* MODULE */
+
#endif /* _PLATFORM_DEVICE_H_ */
projects / deliverable / linux.git / commitdiff
