platform: Add support for automatic device IDs

Right now we have support for explicit platform device IDs, as well as
ID-less platform devices when a given device type can only have one
instance. However there are cases where multiple instances of a device
type can exist, and their IDs aren't (and can't be) known in advance
and do not matter. In that case we need automatic device IDs to avoid
device name collisions.

I am using magic ID value -2 (PLATFORM_DEVID_AUTO) for this, similar
to -1 for ID-less devices. The automatically allocated device IDs are
global (to avoid an additional per-driver cost.) We keep note that the
ID was automatically allocated so that it can be freed later.

Note that we also restore the ID to PLATFORM_DEVID_AUTO on error and
device deletion, to avoid avoid unexpected behavior on retry. I don't
really expect retries on platform device addition, but better safe
than sorry.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index a1a72250258705eb059b6601b086cf9d296b1d1b..3f8077ce585ca52ea99bf7251b446fb53f1cc7ca 100644 (file)
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -20,9 +20,13 @@
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/pm_runtime.h>
+#include <linux/idr.h>
 
 #include "base.h"
 
+/* For automatically allocated device IDs */
+static DEFINE_IDA(platform_devid_ida);
+
 #define to_platform_driver(drv)        (container_of((drv), struct platform_driver, \
                                 driver))
 
@@ -263,7 +267,7 @@ EXPORT_SYMBOL_GPL(platform_device_add_data);
  */
 int platform_device_add(struct platform_device *pdev)
 {
-       int i, ret = 0;
+       int i, ret;
 
        if (!pdev)
                return -EINVAL;
@@ -273,10 +277,27 @@ int platform_device_add(struct platform_device *pdev)
 
        pdev->dev.bus = &platform_bus_type;
 
-       if (pdev->id != -1)
+       switch (pdev->id) {
+       default:
                dev_set_name(&pdev->dev, "%s.%d", pdev->name,  pdev->id);
-       else
+               break;
+       case PLATFORM_DEVID_NONE:
                dev_set_name(&pdev->dev, "%s", pdev->name);
+               break;
+       case PLATFORM_DEVID_AUTO:
+               /*
+                * Automatically allocated device ID. We mark it as such so
+                * that we remember it must be freed, and we append a suffix
+                * to avoid namespace collision with explicit IDs.
+                */
+               ret = ida_simple_get(&platform_devid_ida, 0, 0, GFP_KERNEL);
+               if (ret < 0)
+                       goto err_out;
+               pdev->id = ret;
+               pdev->id_auto = true;
+               dev_set_name(&pdev->dev, "%s.%d.auto", pdev->name, pdev->id);
+               break;
+       }
 
        for (i = 0; i < pdev->num_resources; i++) {
                struct resource *p, *r = &pdev->resource[i];
@@ -309,6 +330,11 @@ int platform_device_add(struct platform_device *pdev)
                return ret;
 
  failed:
+       if (pdev->id_auto) {
+               ida_simple_remove(&platform_devid_ida, pdev->id);
+               pdev->id = PLATFORM_DEVID_AUTO;
+       }
+
        while (--i >= 0) {
                struct resource *r = &pdev->resource[i];
                unsigned long type = resource_type(r);
@@ -317,6 +343,7 @@ int platform_device_add(struct platform_device *pdev)
                        release_resource(r);
        }
 
+ err_out:
        return ret;
 }
 EXPORT_SYMBOL_GPL(platform_device_add);
@@ -336,6 +363,11 @@ void platform_device_del(struct platform_device *pdev)
        if (pdev) {
                device_del(&pdev->dev);
 
+               if (pdev->id_auto) {
+                       ida_simple_remove(&platform_devid_ida, pdev->id);
+                       pdev->id = PLATFORM_DEVID_AUTO;
+               }
+
                for (i = 0; i < pdev->num_resources; i++) {
                        struct resource *r = &pdev->resource[i];
                        unsigned long type = resource_type(r);

diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index 60e9994ef4053ef120ff65def32de3c2940a2d9f..5711e9525a2a80b3c405438632ea95b17a5836c9 100644 (file)
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -14,11 +14,15 @@
 #include <linux/device.h>
 #include <linux/mod_devicetable.h>
 
+#define PLATFORM_DEVID_NONE    (-1)
+#define PLATFORM_DEVID_AUTO    (-2)
+
 struct mfd_cell;
 
 struct platform_device {
        const char      * name;
        int             id;
+       bool            id_auto;
        struct device   dev;
        u32             num_resources;
        struct resource * resource;