From 3c7a9be77d2dbc037728226b103f9c57e49bcaad Mon Sep 17 00:00:00 2001
From: Jeremy Kerr <jk@codeconstruct.com.au>
Date: Wed, 13 Jul 2022 13:19:24 +0800
Subject: [PATCH] nvme: Introduce a union in struct nvme_dev for different
 transport types

This change modifies struct nvme_dev to allow for future transport
types, by moving the transport-specific data into a union. We will add
new types in a future change.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
---
 nvme.c | 10 ++++++----
 nvme.h | 27 +++++++++++++++++++++++----
 2 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/nvme.c b/nvme.c
index 50099a92..95c23ed4 100644
--- a/nvme.c
+++ b/nvme.c
@@ -207,12 +207,12 @@ static ssize_t getrandom_bytes(void *buf, size_t buflen)
 
 static bool is_chardev(struct nvme_dev *dev)
 {
-	return S_ISCHR(dev->stat.st_mode);
+	return S_ISCHR(dev->direct.stat.st_mode);
 }
 
 static bool is_blkdev(struct nvme_dev *dev)
 {
-	return S_ISBLK(dev->stat.st_mode);
+	return S_ISBLK(dev->direct.stat.st_mode);
 }
 
 static int open_dev(struct nvme_dev **devp, char *devstr, int flags)
@@ -223,15 +223,17 @@ static int open_dev(struct nvme_dev **devp, char *devstr, int flags)
 	dev = calloc(1, sizeof(*dev));
 	if (!dev)
 		return -1;
+
+	dev->type = NVME_DEV_DIRECT;
 	dev->name = basename(devstr);
 	err = open(devstr, flags);
 	if (err < 0) {
 		perror(devstr);
 		goto err_free;
 	}
-	dev->fd = err;
+	dev->direct.fd = err;
 
-	err = fstat(dev_fd(dev), &dev->stat);
+	err = fstat(dev_fd(dev), &dev->direct.stat);
 	if (err < 0) {
 		perror(devstr);
 		goto err_close;
diff --git a/nvme.h b/nvme.h
index 549cd9cd..0f0f1ead 100644
--- a/nvme.h
+++ b/nvme.h
@@ -19,6 +19,7 @@
 #include <dirent.h>
 #include <stdbool.h>
 #include <stdint.h>
+#include <stdio.h>
 #include <endian.h>
 #include <sys/time.h>
 #include <sys/stat.h>
@@ -37,15 +38,33 @@ enum nvme_print_flags {
 
 #define SYS_NVME "/sys/class/nvme"
 
+enum nvme_dev_type {
+	NVME_DEV_DIRECT,
+};
+
 struct nvme_dev {
-	int fd;
-	struct stat stat;
+	enum nvme_dev_type type;
+	union {
+		struct {
+			int fd;
+			struct stat stat;
+		} direct;
+	};
+
 	const char *name;
 };
 
-static inline int dev_fd(struct nvme_dev *dev)
+#define dev_fd(d) __dev_fd(d, __func__, __LINE__)
+
+static inline int __dev_fd(struct nvme_dev *dev, const char *func, int line)
 {
-	return dev->fd;
+	if (dev->type != NVME_DEV_DIRECT) {
+		fprintf(stderr,
+			"warning: %s:%d not a direct transport!\n",
+			func, line);
+		return -1;
+	}
+	return dev->direct.fd;
 }
 
 void register_extension(struct plugin *plugin);
-- 
2.50.1