[PATCH v2 08/21] block, blksnap: interaction with sysfs

[Sergei Shtepa]

Provides creation of a class file /sys/class/blksnap and a device file
/dev/blksnap for module management.

Signed-off-by: Sergei Shtepa <sergei.shtepa@xxxxxxxxx>
---
 drivers/block/blksnap/sysfs.c | 80 +++++++++++++++++++++++++++++++++++
 drivers/block/blksnap/sysfs.h |  7 +++
 2 files changed, 87 insertions(+)
 create mode 100644 drivers/block/blksnap/sysfs.c
 create mode 100644 drivers/block/blksnap/sysfs.h

diff --git a/drivers/block/blksnap/sysfs.c b/drivers/block/blksnap/sysfs.c
new file mode 100644
index 000000000000..6f53c4217d6c
--- /dev/null
+++ b/drivers/block/blksnap/sysfs.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+#define pr_fmt(fmt) KBUILD_MODNAME "-sysfs: " fmt
+
+#include <linux/module.h>
+#include <linux/blkdev.h>
+#include <linux/sysfs.h>
+#include <linux/device.h>
+#include <uapi/linux/blksnap.h>
+#include "sysfs.h"
+#include "ctrl.h"
+
+static ssize_t major_show(struct class *class, struct class_attribute *attr,
+			  char *buf)
+{
+	sprintf(buf, "%d", get_blk_snap_major());
+	return strlen(buf);
+}
+
+/* Declare class_attr_major */
+CLASS_ATTR_RO(major);
+
+static struct class *blk_snap_class;
+
+static struct device *blk_snap_device;
+
+int sysfs_initialize(void)
+{
+	struct device *dev;
+	int res;
+
+	blk_snap_class = class_create(THIS_MODULE, THIS_MODULE->name);
+	if (IS_ERR(blk_snap_class)) {
+		res = PTR_ERR(blk_snap_class);
+
+		pr_err("Bad class create. errno=%d\n", abs(res));
+		return res;
+	}
+
+	pr_info("Create 'major' sysfs attribute\n");
+	res = class_create_file(blk_snap_class, &class_attr_major);
+	if (res) {
+		pr_err("Failed to create 'major' sysfs file\n");
+
+		class_destroy(blk_snap_class);
+		blk_snap_class = NULL;
+		return res;
+	}
+
+	dev = device_create(blk_snap_class, NULL,
+			    MKDEV(get_blk_snap_major(), 0), NULL,
+			    THIS_MODULE->name);
+	if (IS_ERR(dev)) {
+		res = PTR_ERR(dev);
+		pr_err("Failed to create device, errno=%d\n", abs(res));
+
+		class_remove_file(blk_snap_class, &class_attr_major);
+		class_destroy(blk_snap_class);
+		blk_snap_class = NULL;
+		return res;
+	}
+
+	blk_snap_device = dev;
+	return res;
+}
+
+void sysfs_finalize(void)
+{
+	pr_info("Cleanup sysfs\n");
+
+	if (blk_snap_device) {
+		device_unregister(blk_snap_device);
+		blk_snap_device = NULL;
+	}
+
+	if (blk_snap_class != NULL) {
+		class_remove_file(blk_snap_class, &class_attr_major);
+		class_destroy(blk_snap_class);
+		blk_snap_class = NULL;
+	}
+}
diff --git a/drivers/block/blksnap/sysfs.h b/drivers/block/blksnap/sysfs.h
new file mode 100644
index 000000000000..5fc200d36789
--- /dev/null
+++ b/drivers/block/blksnap/sysfs.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __BLK_SNAP_SYSFS_H
+#define __BLK_SNAP_SYSFS_H
+
+int sysfs_initialize(void);
+void sysfs_finalize(void);
+#endif /* __BLK_SNAP_SYSFS_H */
-- 
2.20.1