[PATCH] platform_bus learns about modalias

This patch adds modalias support to platform devices, for simpler
hotplug/coldplug driven driver setup.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 83f5c5984d1a..f8071976fe07 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -452,6 +452,37 @@ void platform_driver_unregister(struct platform_driver *drv)
 EXPORT_SYMBOL_GPL(platform_driver_unregister);
 
 
+/* modalias support enables more hands-off userspace setup:
+ * (a) environment variable lets new-style hotplug events work once system is
+ *     fully running:  "modprobe $MODALIAS"
+ * (b) sysfs attribute lets new-style coldplug recover from hotplug events
+ *     mishandled before system is fully running:  "modprobe $(cat modalias)"
+ */
+static ssize_t
+modalias_show(struct device *dev, struct device_attribute *a, char *buf)
+{
+        struct platform_device  *pdev = to_platform_device(dev);
+        int len = snprintf(buf, PAGE_SIZE, "%s\n", pdev->name);
+
+        return (len >= PAGE_SIZE) ? (PAGE_SIZE - 1) : len;
+}
+
+static struct device_attribute platform_dev_attrs[] = {
+        __ATTR_RO(modalias),
+        __ATTR_NULL,
+};
+
+static int platform_uevent(struct device *dev, char **envp, int num_envp,
+                char *buffer, int buffer_size)
+{
+        struct platform_device  *pdev = to_platform_device(dev);
+
+        envp[0] = buffer;
+        snprintf(buffer, buffer_size, "MODALIAS=%s", pdev->name);
+        return 0;
+}
+
+
 /**
  *      platform_match - bind platform device to platform driver.
  *      @dev:   device.
@@ -496,7 +527,9 @@ static int platform_resume(struct device * dev)
 
 struct bus_type platform_bus_type = {
         .name           = "platform",
+        .dev_attrs      = platform_dev_attrs,
         .match          = platform_match,
+        .uevent         = platform_uevent,
         .suspend        = platform_suspend,
         .resume         = platform_resume,
 };