Driver Core: early platform driver

V3 of the early platform driver implementation.

Platform drivers are great for embedded platforms because we can separate
driver configuration from the actual driver.  So base addresses,
interrupts and other configuration can be kept with the processor or board
code, and the platform driver can be reused by many different platforms.

For early devices we have nothing today.  For instance, to configure early
timers and early serial ports we cannot use platform devices.  This
because the setup order during boot.  Timers are needed before the
platform driver core code is available.  The same goes for early printk
support.  Early in this case means before initcalls.

These early drivers today have their configuration either hard coded or
they receive it using some special configuration method.  This is working
quite well, but if we want to support both regular kernel modules and
early devices then we need to have two ways of configuring the same
driver.  A single way would be better.

The early platform driver patch is basically a set of functions that allow
drivers to register themselves and architecture code to locate them and
probe.  Registration happens through early_param().  The time for the
probe is decided by the architecture code.

See Documentation/driver-model/platform.txt for more details.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Magnus Damm <damm@igel.co.jp>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: David Brownell <david-b@pacbell.net>
Cc: Tejun Heo <htejun@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 239 insertions, 0 deletions

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index d2198f64ad4e..b5b6c973a2e0 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -990,6 +990,8 @@ int __init platform_bus_init(void)
 {
         int error;
 
+        early_platform_cleanup();
+
         error = device_register(&platform_bus);
         if (error)
                 return error;
@@ -1020,3 +1022,240 @@ u64 dma_get_required_mask(struct device *dev)
 }
 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));
+        }
+}
+