[Xen-devel] [PATCH 6 of 9 RFC] blktap3: Introduce tapdisk control information retrieval functionality

[Thanos Makatos <thanos.makatos@xxxxxxxxxx>]

This patch introduces files control/tap-ctl-info.[ch]. Function tap_ctl_info is
used by the xenio daemon to retrieve the size of the block device, as well as
the sector size,  in order to communicate it to blkfront so that it can create
the virtual block device.

diff --git a/tools/blktap3/control/tap-ctl-info.c 
b/tools/blktap3/control/tap-ctl-info.c
new file mode 100644
--- /dev/null
+++ b/tools/blktap3/control/tap-ctl-info.c
@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2012      Citrix Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "tap-ctl.h"
+#include "tap-ctl-info.h"
+
+int tap_ctl_info(pid_t pid, int minor, unsigned long long *sectors,
+        unsigned int *sector_size, unsigned int *info)
+{
+    tapdisk_message_t message;
+    int err;
+
+    memset(&message, 0, sizeof(message));
+    message.type = TAPDISK_MESSAGE_DISK_INFO;
+    message.cookie = minor;
+
+    err = tap_ctl_connect_send_and_receive(pid, &message, NULL);
+    if (err)
+        return err;
+
+    if (message.type != TAPDISK_MESSAGE_DISK_INFO_RSP)
+        return -EINVAL;
+
+    *sectors = message.u.image.sectors;
+    *sector_size = message.u.image.sector_size;
+    *info = message.u.image.info;
+    return err;
+}
diff --git a/tools/blktap3/control/tap-ctl-info.h 
b/tools/blktap3/control/tap-ctl-info.h
new file mode 100644
--- /dev/null
+++ b/tools/blktap3/control/tap-ctl-info.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2012      Citrix Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ */
+
+#ifndef __TAP_CTL_INFO_H__
+#define __TAP_CTL_INFO_H__
+
+/**
+ * Retrieves virtual disk information from a tapdisk.
+ *
+ * @pid the process ID of the tapdisk process
+ * @minor the minor device number
+ * @sectors output parameter that receives the number of sectors
+ * @sector_size output parameter that receives the size of the sector
+ * @info TODO ?
+ * 
+ */
+int tap_ctl_info(pid_t pid, int minor, unsigned long long *sectors,
+        unsigned int *sector_size, unsigned int *info);
+
+#endif /* __TAP_CTL_INFO_H__ */

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