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Subject[PATCH 18/19] mfd-core: add platform_device sharing support for mfd

This adds functions to enable platform_device sharing for mfd clients.

Each platform driver (mfd client) that wants to share an mfd_cell's
platform_device uses the mfd_shared_platform_driver_{un,}register()
functions instead of platform_driver_{un,}register(). Along with
registering the platform driver, these also register a new platform
device with the same characteristics as the original, but a different
name. Given an mfd_cell with the name "foo", the first call to
mfd_shared_platform_driver_register will register a platform device
named "foo0", as well as an associated platform_driver named "foo0".
The second call would register a platform device and driver with the
name "foo1", and so on.
This deals with platform handling only; mfd driver-specific details,
hardware handling, refcounting, etc are all dealt with separately.

Signed-off-by: Andres Salomon <dilinger@queued.net>
---
drivers/mfd/mfd-core.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/mfd/core.h | 9 ++++
2 files changed, 124 insertions(+), 0 deletions(-)
diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
index 90e9483..a27a377 100644
--- a/drivers/mfd/mfd-core.c
+++ b/drivers/mfd/mfd-core.c
@@ -172,5 +172,120 @@ void mfd_remove_devices(struct device *parent)
}
EXPORT_SYMBOL(mfd_remove_devices);

+/*
+ * Find the first available platform_driver name, appending decimals
+ * after the name. That is, given the string "foo", check whether
+ * "foo0", "foo1", "foo2", etc are in use. Once a name is found
+ * that isn't in use, fill in *newname with it.
+ *
+ * If this returns non-zero, *newname must be kfree()d.
+ */
+static int get_unique_driver_name(const char *oldname, char **newname)
+{
+ struct device_driver *drv;
+ char *endp;
+ size_t len;
+ int i;
+
+ /* allocate memory for new name; includes space for extra 2 digits */
+ len = strlen(oldname);
+ *newname = kmalloc(len + 3, GFP_KERNEL);
+ if (!*newname)
+ return -ENOMEM;
+ endp = strcpy(*newname, oldname) + len;
+ BUG_ON(*endp != '\0');
+
+ /* search for the first driver name available */
+ for (i = 0; i < 99; i++) {
+ sprintf(endp, "%d", i);
+ drv = driver_find(*newname, &platform_bus_type);
+ if (!drv)
+ break;
+ put_driver(drv);
+ }
+
+ if (i > 99) {
+ /* we have too many subdevices registered? allow up to 99. */
+ kfree(*newname);
+ return -ENODEV;
+ }
+
+ return 0;
+}
+
+static int add_shared_platform_device(const char *cell, const char *name)
+{
+ struct mfd_cell cell_entry;
+ struct device *dev;
+ struct platform_device *pdev;
+ int err;
+
+ /* check if we've already registered a device (don't fail if we have) */
+ if (bus_find_device_by_name(&platform_bus_type, NULL, name))
+ return 0;
+
+ /* fetch the parent cell's device (should already be registered!) */
+ dev = bus_find_device_by_name(&platform_bus_type, NULL, cell);
+ if (!dev) {
+ printk(KERN_ERR "failed to find device for cell %s\n", cell);
+ return -ENODEV;
+ }
+ pdev = to_platform_device(dev);
+ memcpy(&cell_entry, mfd_get_cell(pdev), sizeof(cell_entry));
+
+ WARN_ON(!cell_entry.enable);
+
+printk(KERN_WARNING "found cell %s, registering platform device %s\n", cell_entry.name, name);
+ cell_entry.name = name;
+ err = mfd_add_device(pdev->dev.parent, -1, &cell_entry, NULL, 0);
+ if (err)
+ dev_err(dev, "MFD add devices failed: %d\n", err);
+ return err;
+}
+
+int mfd_shared_platform_driver_register(struct platform_driver *drv,
+ const char *cellname)
+{
+ char *unique = NULL;
+ int err;
+
+ err = get_unique_driver_name(cellname, &unique);
+ if (err)
+ return err;
+printk(KERN_WARNING "registering platform device %s\n", unique);
+
+ err = add_shared_platform_device(cellname, unique);
+ if (err)
+ printk(KERN_ERR "failed to add platform device %s\n", unique);
+
+printk(KERN_WARNING "registering platform driver %s\n", unique);
+
+ drv->driver.name = unique;
+ err = platform_driver_register(drv);
+ if (err)
+ kfree(unique);
+/* TODO: if cs5535-mfd is already loaded, need to create devices as well */
+
+ return err;
+}
+EXPORT_SYMBOL(mfd_shared_platform_driver_register);
+
+void mfd_shared_platform_driver_unregister(struct platform_driver *drv)
+{
+ struct device *dev;
+
+printk(KERN_WARNING "unregistering platform device %s\n", drv->driver.name);
+ dev = bus_find_device_by_name(&platform_bus_type, NULL,
+ drv->driver.name);
+ if (dev)
+ platform_device_unregister(to_platform_device(dev));
+
+printk(KERN_WARNING "unregistering platform driver %s\n", drv->driver.name);
+ platform_driver_unregister(drv);
+ kfree(drv->driver.name);
+ drv->driver.name = NULL;
+}
+EXPORT_SYMBOL(mfd_shared_platform_driver_unregister);
+
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ian Molton, Dmitry Baryshkov");
diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h
index d13b992..ee1dd83 100644
--- a/include/linux/mfd/core.h
+++ b/include/linux/mfd/core.h
@@ -78,4 +78,13 @@ extern int mfd_add_devices(struct device *parent, int id,

extern void mfd_remove_devices(struct device *parent);

+/*
+ * For MFD drivers with clients sharing access to resources, these create
+ * multiple platform devices per cell. Contention handling must still be
+ * handled via drivers (ie, with enable/disable hooks).
+ */
+extern int mfd_shared_platform_driver_register(struct platform_driver *drv,
+ const char *cellname);
+extern void mfd_shared_platform_driver_unregister(struct platform_driver *drv);
+
#endif
--
1.7.2.3


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