msm: subsystem_restart: Add a device node for each subsystem
Add a device node for each subsystem to help in trouble-free
ref counting by associating subsystem_get() with open() and
subsystem_put() with close() on the device file. This allows
userspace to power up/down subsystems directly. This should be
exposed via a userspace library and friendlier APIs. Having a
device node is a better idea than having debugfs nodes because
even if the user space process gets killed all open()'ed file
descriptors for that process will close()'ed automatically.
The same can't be said of debugfs nodes which we currently
have now. Besides, debugfs nodes may or may not be available
on commercial builds. So, add a device node for each subsystem.
Change-Id: I7a105ab7217245afb3b7702245647f57d32174c8
Signed-off-by: Seemanta Dutta <seemanta@codeaurora.org>
diff --git a/arch/arm/mach-msm/subsystem_restart.c b/arch/arm/mach-msm/subsystem_restart.c
index 4957a67..29481d3 100644
--- a/arch/arm/mach-msm/subsystem_restart.c
+++ b/arch/arm/mach-msm/subsystem_restart.c
@@ -30,6 +30,7 @@
#include <linux/device.h>
#include <linux/idr.h>
#include <linux/debugfs.h>
+#include <linux/miscdevice.h>
#include <asm/current.h>
@@ -144,6 +145,8 @@
struct dentry *dentry;
#endif
bool do_ramdump_on_put;
+ struct miscdevice misc_dev;
+ char miscdevice_name[32];
};
static struct subsys_device *to_subsys(struct device *d)
@@ -850,6 +853,41 @@
static void subsys_debugfs_remove(struct subsys_device *subsys) { }
#endif
+static int subsys_device_open(struct inode *inode, struct file *file)
+{
+ void *retval;
+ struct subsys_device *subsys_dev = container_of(file->private_data,
+ struct subsys_device, misc_dev);
+
+ if (!file->private_data)
+ return -EINVAL;
+
+ retval = subsystem_get(subsys_dev->desc->name);
+ if (IS_ERR(retval))
+ return PTR_ERR(retval);
+
+ return 0;
+}
+
+static int subsys_device_close(struct inode *inode, struct file *file)
+{
+ struct subsys_device *subsys_dev = container_of(file->private_data,
+ struct subsys_device, misc_dev);
+
+ if (!file->private_data)
+ return -EINVAL;
+
+ subsystem_put(subsys_dev);
+
+ return 0;
+}
+
+static const struct file_operations subsys_device_fops = {
+ .owner = THIS_MODULE,
+ .open = subsys_device_open,
+ .release = subsys_device_close,
+};
+
static void subsys_device_release(struct device *dev)
{
struct subsys_device *subsys = to_subsys(dev);
@@ -860,6 +898,33 @@
kfree(subsys);
}
+static int subsys_misc_device_add(struct subsys_device *subsys_dev)
+{
+ int ret;
+ memset(subsys_dev->miscdevice_name, 0,
+ ARRAY_SIZE(subsys_dev->miscdevice_name));
+ snprintf(subsys_dev->miscdevice_name,
+ ARRAY_SIZE(subsys_dev->miscdevice_name), "subsys_%s",
+ subsys_dev->desc->name);
+
+ subsys_dev->misc_dev.minor = MISC_DYNAMIC_MINOR;
+ subsys_dev->misc_dev.name = subsys_dev->miscdevice_name;
+ subsys_dev->misc_dev.fops = &subsys_device_fops;
+ subsys_dev->misc_dev.parent = &subsys_dev->dev;
+
+ ret = misc_register(&subsys_dev->misc_dev);
+ if (ret) {
+ pr_err("%s: misc_register() failed for %s (%d)", __func__,
+ subsys_dev->miscdevice_name, ret);
+ }
+ return ret;
+}
+
+static void subsys_misc_device_remove(struct subsys_device *subsys_dev)
+{
+ misc_deregister(&subsys_dev->misc_dev);
+}
+
struct subsys_device *subsys_register(struct subsys_desc *desc)
{
struct subsys_device *subsys;
@@ -898,6 +963,12 @@
ret = device_register(&subsys->dev);
if (ret) {
+ device_unregister(&subsys->dev);
+ goto err_register;
+ }
+
+ ret = subsys_misc_device_add(subsys);
+ if (ret) {
put_device(&subsys->dev);
goto err_register;
}
@@ -927,6 +998,7 @@
device_unregister(&subsys->dev);
mutex_unlock(&subsys->track.lock);
subsys_debugfs_remove(subsys);
+ subsys_misc_device_remove(subsys);
put_device(&subsys->dev);
}
}