libnvdimm, e820: make CONFIG_X86_PMEM_LEGACY a tristate option

We currently register a platform device for e820 type-12 memory and
register a nvdimm bus beneath it.  Registering the platform device
triggers the device-core machinery to probe for a driver, but that
search currently comes up empty.  Building the nvdimm-bus registration
into the e820_pmem platform device registration in this way forces
libnvdimm to be built-in.  Instead, convert the built-in portion of
CONFIG_X86_PMEM_LEGACY to simply register a platform device and move the
rest of the logic to the driver for e820_pmem, for the following
reasons:

1/ Letting e820_pmem support be a module allows building and testing
   libnvdimm.ko changes without rebooting

2/ All the normal policy around modules can be applied to e820_pmem
   (unbind to disable and/or blacklisting the module from loading by
   default)

3/ Moving the driver to a generic location and converting it to scan
   "iomem_resource" rather than "e820.map" means any other architecture can
   take advantage of this simple nvdimm resource discovery mechanism by
   registering a resource named "Persistent Memory (legacy)"

Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 86 insertions, 0 deletions

diff --git a/drivers/nvdimm/e820.c b/drivers/nvdimm/e820.c
new file mode 100644
index 000000000000..1b5743ad92db
--- /dev/null
+++ b/drivers/nvdimm/e820.c
@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2015, Christoph Hellwig.
+ * Copyright (c) 2015, Intel Corporation.
+ */
+#include <linux/platform_device.h>
+#include <linux/libnvdimm.h>
+#include <linux/module.h>
+
+static const struct attribute_group *e820_pmem_attribute_groups[] = {
+	&nvdimm_bus_attribute_group,
+	NULL,
+};
+
+static const struct attribute_group *e820_pmem_region_attribute_groups[] = {
+	&nd_region_attribute_group,
+	&nd_device_attribute_group,
+	NULL,
+};
+
+static int e820_pmem_remove(struct platform_device *pdev)
+{
+	struct nvdimm_bus *nvdimm_bus = platform_get_drvdata(pdev);
+
+	nvdimm_bus_unregister(nvdimm_bus);
+	return 0;
+}
+
+static int e820_pmem_probe(struct platform_device *pdev)
+{
+	static struct nvdimm_bus_descriptor nd_desc;
+	struct device *dev = &pdev->dev;
+	struct nvdimm_bus *nvdimm_bus;
+	struct resource *p;
+
+	nd_desc.attr_groups = e820_pmem_attribute_groups;
+	nd_desc.provider_name = "e820";
+	nvdimm_bus = nvdimm_bus_register(dev, &nd_desc);
+	if (!nvdimm_bus)
+		goto err;
+	platform_set_drvdata(pdev, nvdimm_bus);
+
+	for (p = iomem_resource.child; p ; p = p->sibling) {
+		struct nd_region_desc ndr_desc;
+
+		if (strncmp(p->name, "Persistent Memory (legacy)", 26) != 0)
+			continue;
+
+		memset(&ndr_desc, 0, sizeof(ndr_desc));
+		ndr_desc.res = p;
+		ndr_desc.attr_groups = e820_pmem_region_attribute_groups;
+		ndr_desc.numa_node = NUMA_NO_NODE;
+		if (!nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc))
+			goto err;
+	}
+
+	return 0;
+
+ err:
+	nvdimm_bus_unregister(nvdimm_bus);
+	dev_err(dev, "failed to register legacy persistent memory ranges\n");
+	return -ENXIO;
+}
+
+static struct platform_driver e820_pmem_driver = {
+	.probe = e820_pmem_probe,
+	.remove = e820_pmem_remove,
+	.driver = {
+		.name = "e820_pmem",
+	},
+};
+
+static __init int e820_pmem_init(void)
+{
+	return platform_driver_register(&e820_pmem_driver);
+}
+
+static __exit void e820_pmem_exit(void)
+{
+	platform_driver_unregister(&e820_pmem_driver);
+}
+
+MODULE_ALIAS("platform:e820_pmem*");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Intel Corporation");
+module_init(e820_pmem_init);
+module_exit(e820_pmem_exit);