[Xen-devel] [PATCH 3 of 9 RFC] blktap3: Introduce the tapdisk control header

[Thanos Makatos <thanos.makatos@xxxxxxxxxx>]

This patch introduces the header file where tapdisk control-related structures
and functions are declared. This file is based on the existing blktap2, with
most changes coming from blktap2 living in github. Linux lists are replaced by
BSD tail queues. Few functions are partly documented, most of them are not
documented at all, this will be addressed by a future patch.

diff --git a/tools/blktap2/control/tap-ctl.h b/tools/blktap3/control/tap-ctl.h
copy from tools/blktap2/control/tap-ctl.h
copy to tools/blktap3/control/tap-ctl.h
--- a/tools/blktap2/control/tap-ctl.h
+++ b/tools/blktap3/control/tap-ctl.h
@@ -30,72 +30,180 @@
 
 #include <syslog.h>
 #include <errno.h>
+#include <sys/time.h>
 #include <tapdisk-message.h>
+#include "blktap3.h"
 
+/*
+ * TODO These are private, move to an internal header.
+ */
 extern int tap_ctl_debug;
 
 #ifdef TAPCTL
-#define DBG(_f, _a...)                         \
-       do {                                    \
+#define DBG(_f, _a...)                 \
+       do {                                            \
                if (tap_ctl_debug)              \
                        printf(_f, ##_a);       \
        } while (0)
 
 #define DPRINTF(_f, _a...) syslog(LOG_INFO, _f, ##_a)
 #define EPRINTF(_f, _a...) syslog(LOG_ERR, "tap-err:%s: " _f, __func__, ##_a)
-#define  PERROR(_f, _a...) syslog(LOG_ERR, "tap-err:%s: " _f ": %s", __func__, 
##_a, \
-                                 strerror(errno))
+#define PERROR(_f, _a...) syslog(LOG_ERR, "tap-err:%s: " _f ": %s", \
+        __func__, ##_a, strerror(errno))
 #endif
 
-void tap_ctl_version(int *major, int *minor);
-int tap_ctl_kernel_version(int *major, int *minor);
+/**
+ * Contains information about a tapdisk process.
+ */
+typedef struct tap_list {
 
-int tap_ctl_check_blktap(const char **message);
-int tap_ctl_check_version(const char **message);
-int tap_ctl_check(const char **message);
+    /**
+     * The process ID.
+     */
+    pid_t pid;
 
+    /**
+     * TODO
+     */
+    int minor;
+
+    /**
+     * State of the VBD, specified in drivers/tapdisk-vbd.h.
+     */
+    int state;
+
+    /**
+     * TODO
+     */
+    char *type;
+
+    /**
+     * /path/to/file
+     */
+    char *path;
+
+    /**
+     * for linked lists
+     */
+    TAILQ_ENTRY(tap_list) entry;
+} tap_list_t;
+
+TAILQ_HEAD(tqh_tap_list, tap_list);
+
+/**
+ * Iterate over a list of struct tap_list elements.
+ */
+#define tap_list_for_each_entry(_pos, _head) \
+    TAILQ_FOREACH(_pos, _head, entry)
+
+/**
+ * Iterate over a list of struct tap_list elements allowing deletions without
+ * having to restart the iteration.
+ */
+#define tap_list_for_each_entry_safe(_pos, _n, _head) \
+    TAILQ_FOREACH_SAFE(_pos, _head, entry, _n)
+
+/**
+ * Connects to a tapdisk.
+ *
+ * @param /path/to/file of the control socket (e.g. 
+ * /var/run/blktap-control/ctl/<pid>
+ * @param socket output parameter that receives the connection
+ * @returns 0 on success, an error code otherwise
+ */
 int tap_ctl_connect(const char *path, int *socket);
-int tap_ctl_connect_id(int id, int *socket);
-int tap_ctl_read_message(int fd, tapdisk_message_t *message, int timeout);
-int tap_ctl_write_message(int fd, tapdisk_message_t *message, int timeout);
-int tap_ctl_send_and_receive(int fd, tapdisk_message_t *message, int timeout);
-int tap_ctl_connect_send_and_receive(int id,
-                                    tapdisk_message_t *message, int timeout);
+
+/**
+ * Connects to a tapdisk.
+ *
+ * @param id the process ID of the tapdisk to connect to
+ * @param socket output parameter that receives the connection
+ * @returns 0 on success, an error code otherwise
+ */
+int tap_ctl_connect_id(const int id, int *socket);
+
+/**
+ * Reads from the tapdisk connection to the buffer.
+ *
+ * @param fd the file descriptor of the socket to read from
+ * @param buf buffer that receives the output
+ * @param sz size, in bytes, of the buffer
+ * @param timeout (optional) specifies the maximum time to wait for reading
+ * @returns 0 on success, an error code otherwise
+ */
+int tap_ctl_read_raw(const int fd, void *buf, const size_t sz,
+        struct timeval *timeout);
+
+int tap_ctl_read_message(int fd, tapdisk_message_t * message,
+        struct timeval *timeout);
+
+int tap_ctl_write_message(int fd, tapdisk_message_t * message,
+        struct timeval *timeout);
+
+int tap_ctl_send_and_receive(int fd, tapdisk_message_t * message,
+        struct timeval *timeout);
+
+int tap_ctl_connect_send_and_receive(int id, tapdisk_message_t * message,
+        struct timeval *timeout);
+
 char *tap_ctl_socket_name(int id);
 
-typedef struct {
-       int         id;
-       pid_t       pid;
-       int         minor;
-       int         state;
-       char       *type;
-       char       *path;
-} tap_list_t;
+int tap_ctl_list_pid(pid_t pid, struct tqh_tap_list *list);
 
-int tap_ctl_get_driver_id(const char *handle);
+/**
+ * Retrieves a list of all tapdisks.
+ *
+ * @param list output parameter that receives the list of tapdisks
+ * @returns 0 on success, an error code otherwise
+ */
+int tap_ctl_list(struct tqh_tap_list *list);
 
-int tap_ctl_list(tap_list_t ***list);
-void tap_ctl_free_list(tap_list_t **list);
-int tap_ctl_find(const char *type, const char *path, tap_list_t *tap);
+/**
+ * Deallocates a list of struct tap_list.
+ *
+ * @param list the tapdisk information structure to deallocate.
+ */
+void tap_ctl_list_free(struct tqh_tap_list *list);
 
-int tap_ctl_allocate(int *minor, char **devname);
-int tap_ctl_free(const int minor);
+/**
+ * Creates a tapdisk process.
+ *
+ * TODO document parameters
+ * @param params
+ * @param flags
+ * @param prt_minor
+ * @param secondary
+ * @returns 0 on success, en error code otherwise
+ */
+int tap_ctl_create(const char *params, int flags, int prt_minor,
+        char *secondary);
 
-int tap_ctl_create(const char *params, char **devname);
-int tap_ctl_destroy(const int id, const int minor);
+int tap_ctl_destroy(const int id, const int minor, int force,
+        struct timeval *timeout);
 
+/*
+ * TODO The following functions are not currently used by anything else
+ * other than the tapdisk itself. Move to a private header?
+ */
 int tap_ctl_spawn(void);
 pid_t tap_ctl_get_pid(const int id);
 
 int tap_ctl_attach(const int id, const int minor);
 int tap_ctl_detach(const int id, const int minor);
 
-int tap_ctl_open(const int id, const int minor, const char *params);
-int tap_ctl_close(const int id, const int minor, const int force);
+int tap_ctl_open(const int id, const int minor, const char *params,
+        int flags, const int prt_minor, const char *secondary);
 
-int tap_ctl_pause(const int id, const int minor);
+int tap_ctl_close(const int id, const int minor, const int force,
+        struct timeval *timeout);
+
+int tap_ctl_pause(const int id, const int minor, struct timeval 
+        *timeout);
+
 int tap_ctl_unpause(const int id, const int minor, const char *params);
 
-int tap_ctl_blk_major(void);
+ssize_t tap_ctl_stats(pid_t pid, int minor, char *buf, size_t size); 
 
-#endif
+int tap_ctl_stats_fwrite(pid_t pid, int minor, FILE * out);
+
+#endif /* __TAP_CTL_H__ */

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