lightnvm: expose device geometry through sysfs

For a host to access an Open-Channel SSD, it has to know its geometry,
so that it writes and reads at the appropriate device bounds.

Currently, the geometry information is kept within the kernel, and not
exported to user-space for consumption. This patch exposes the
configuration through sysfs and enables user-space libraries, such as
liblightnvm, to use the sysfs implementation to get the geometry of an
Open-Channel SSD.

The sysfs entries are stored within the device hierarchy, and can be
found using the "lightnvm" device type.

An example configuration looks like this:

/sys/class/nvme/
└── nvme0n1
   ├── capabilities: 3
   ├── device_mode: 1
   ├── erase_max: 1000000
   ├── erase_typ: 1000000
   ├── flash_media_type: 0
   ├── media_capabilities: 0x00000001
   ├── media_type: 0
   ├── multiplane: 0x00010101
   ├── num_blocks: 1022
   ├── num_channels: 1
   ├── num_luns: 4
   ├── num_pages: 64
   ├── num_planes: 1
   ├── page_size: 4096
   ├── prog_max: 100000
   ├── prog_typ: 100000
   ├── read_max: 10000
   ├── read_typ: 10000
   ├── sector_oob_size: 0
   ├── sector_size: 4096
   ├── media_manager: gennvm
   ├── ppa_format: 0x380830082808001010102008
   ├── vendor_opcode: 0
   ├── max_phys_secs: 64
   └── version: 1

Signed-off-by: Simon A. F. Lund <slund@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/nvme/host/lightnvm.c b/drivers/nvme/host/lightnvm.c
index 798fcd9f5d1f..f5e3011e31fc 100644
--- a/drivers/nvme/host/lightnvm.c
+++ b/drivers/nvme/host/lightnvm.c
@@ -592,7 +592,8 @@ static struct nvm_dev_ops nvme_nvm_dev_ops = {
 	.max_phys_sect		= 64,
 };
 
-int nvme_nvm_register(struct nvme_ns *ns, char *disk_name, int node)
+int nvme_nvm_register(struct nvme_ns *ns, char *disk_name, int node,
+		      const struct attribute_group *attrs)
 {
 	struct request_queue *q = ns->queue;
 	struct nvm_dev *dev;
@@ -605,19 +606,23 @@ int nvme_nvm_register(struct nvme_ns *ns, char *disk_name, int node)
 	dev->q = q;
 	memcpy(dev->name, disk_name, DISK_NAME_LEN);
 	dev->ops = &nvme_nvm_dev_ops;
+	dev->parent_dev = ns->ctrl->device;
+	dev->private_data = ns;
 	ns->ndev = dev;
 
 	ret = nvm_register(dev);
 
 	ns->lba_shift = ilog2(dev->sec_size) - 9;
 
+	if (sysfs_create_group(&dev->dev.kobj, attrs))
+		pr_warn("%s: failed to create sysfs group for identification\n",
+			disk_name);
 	return ret;
 }
 
 void nvme_nvm_unregister(struct nvme_ns *ns)
 {
 	nvm_unregister(ns->ndev);
-	kfree(ns->ndev);
 }
 
 /* move to shared place when used in multiple places. */