mm/hmm/devmem: dummy HMM device for ZONE_DEVICE memory
[sfrench/cifs-2.6.git] / mm / hmm.c
index afb51078a5cf3fabf7b097e27aaafb7e3782dc7b..c9d23ef80552ff394cc2e8335a858dae6b29e92d 100644 (file)
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -19,6 +19,7 @@
  */
 #include <linux/mm.h>
 #include <linux/hmm.h>
+#include <linux/init.h>
 #include <linux/rmap.h>
 #include <linux/swap.h>
 #include <linux/slab.h>
@@ -1096,4 +1097,84 @@ void hmm_devmem_remove(struct hmm_devmem *devmem)
        devm_release_mem_region(device, start, size);
 }
 EXPORT_SYMBOL(hmm_devmem_remove);
+
+/*
+ * A device driver that wants to handle multiple devices memory through a
+ * single fake device can use hmm_device to do so. This is purely a helper
+ * and it is not needed to make use of any HMM functionality.
+ */
+#define HMM_DEVICE_MAX 256
+
+static DECLARE_BITMAP(hmm_device_mask, HMM_DEVICE_MAX);
+static DEFINE_SPINLOCK(hmm_device_lock);
+static struct class *hmm_device_class;
+static dev_t hmm_device_devt;
+
+static void hmm_device_release(struct device *device)
+{
+       struct hmm_device *hmm_device;
+
+       hmm_device = container_of(device, struct hmm_device, device);
+       spin_lock(&hmm_device_lock);
+       clear_bit(hmm_device->minor, hmm_device_mask);
+       spin_unlock(&hmm_device_lock);
+
+       kfree(hmm_device);
+}
+
+struct hmm_device *hmm_device_new(void *drvdata)
+{
+       struct hmm_device *hmm_device;
+
+       hmm_device = kzalloc(sizeof(*hmm_device), GFP_KERNEL);
+       if (!hmm_device)
+               return ERR_PTR(-ENOMEM);
+
+       spin_lock(&hmm_device_lock);
+       hmm_device->minor = find_first_zero_bit(hmm_device_mask, HMM_DEVICE_MAX);
+       if (hmm_device->minor >= HMM_DEVICE_MAX) {
+               spin_unlock(&hmm_device_lock);
+               kfree(hmm_device);
+               return ERR_PTR(-EBUSY);
+       }
+       set_bit(hmm_device->minor, hmm_device_mask);
+       spin_unlock(&hmm_device_lock);
+
+       dev_set_name(&hmm_device->device, "hmm_device%d", hmm_device->minor);
+       hmm_device->device.devt = MKDEV(MAJOR(hmm_device_devt),
+                                       hmm_device->minor);
+       hmm_device->device.release = hmm_device_release;
+       dev_set_drvdata(&hmm_device->device, drvdata);
+       hmm_device->device.class = hmm_device_class;
+       device_initialize(&hmm_device->device);
+
+       return hmm_device;
+}
+EXPORT_SYMBOL(hmm_device_new);
+
+void hmm_device_put(struct hmm_device *hmm_device)
+{
+       put_device(&hmm_device->device);
+}
+EXPORT_SYMBOL(hmm_device_put);
+
+static int __init hmm_init(void)
+{
+       int ret;
+
+       ret = alloc_chrdev_region(&hmm_device_devt, 0,
+                                 HMM_DEVICE_MAX,
+                                 "hmm_device");
+       if (ret)
+               return ret;
+
+       hmm_device_class = class_create(THIS_MODULE, "hmm_device");
+       if (IS_ERR(hmm_device_class)) {
+               unregister_chrdev_region(hmm_device_devt, HMM_DEVICE_MAX);
+               return PTR_ERR(hmm_device_class);
+       }
+       return 0;
+}
+
+device_initcall(hmm_init);
 #endif /* IS_ENABLED(CONFIG_DEVICE_PRIVATE) */