[Qemu-devel] [PATCH 4/6] QAPI: Introduce memchar_read QMP command

[Lei Li <lilei@linux.vnet.ibm.com>]

Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
---
 hmp-commands.hx  |   16 ++++++++++++++++
 hmp.c            |   15 +++++++++++++++
 hmp.h            |    1 +
 qapi-schema.json |   23 +++++++++++++++++++++++
 qemu-char.c      |   32 ++++++++++++++++++++++++++++++++
 qmp-commands.hx  |   31 +++++++++++++++++++++++++++++++
 6 files changed, 118 insertions(+), 0 deletions(-)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index 829aea1..9f61633 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -813,6 +813,22 @@ to memchr char device with size @var{size}.
 ETEXI
 
     {
+        .name       = "memchar-read",
+        .args_type  = "chardev:s,size:i,format:s?",
+        .params     = "chardev size",
+        .help       = "Provide read interface for memchardev. Read from"
+                      "memchr char device and return 'size' of the data",
+        .mhandler.cmd = hmp_memchar_read,
+    },
+
+STEXI
+@item memchar-read @var{chardev} @var{size} @var{format}
+@findex memchar-read
+Provide read interface for memchardev. Read from memchr
+char device and return @var{size} of the data.
+ETEXI
+
+    {
         .name       = "migrate",
         .args_type  = "detach:-d,blk:-b,inc:-i,uri:s",
         .params     = "[-d] [-b] [-i] uri",
diff --git a/hmp.c b/hmp.c
index c1164eb..0c0182a 100644
--- a/hmp.c
+++ b/hmp.c
@@ -683,6 +683,21 @@ void hmp_memchar_write(Monitor *mon, const QDict *qdict)
     hmp_handle_error(mon, &errp);
 }
 
+void hmp_memchar_read(Monitor *mon, const QDict *qdict)
+{
+    uint32_t size = qdict_get_int(qdict, "size");
+    const char *chardev = qdict_get_str(qdict, "chardev");
+    char *data;
+    int con = qdict_get_try_bool(qdict, "utf8", 0);
+    enum DataFormat format;
+    Error *errp = NULL;
+
+    format = con ? DATA_FORMAT_UTF8 : DATA_FORMAT_BASE64;
+
+    data = qmp_memchar_read(chardev, size, true, format, &errp);
+    monitor_printf(mon, "%s\n", data);
+}
+
 static void hmp_cont_cb(void *opaque, int err)
 {
     if (!err) {
diff --git a/hmp.h b/hmp.h
index 15e1311..b734e31 100644
--- a/hmp.h
+++ b/hmp.h
@@ -44,6 +44,7 @@ void hmp_cpu(Monitor *mon, const QDict *qdict);
 void hmp_memsave(Monitor *mon, const QDict *qdict);
 void hmp_pmemsave(Monitor *mon, const QDict *qdict);
 void hmp_memchar_write(Monitor *mon, const QDict *qdict);
+void hmp_memchar_read(Monitor *mon, const QDict *qdict);
 void hmp_cont(Monitor *mon, const QDict *qdict);
 void hmp_system_wakeup(Monitor *mon, const QDict *qdict);
 void hmp_inject_nmi(Monitor *mon, const QDict *qdict);
diff --git a/qapi-schema.json b/qapi-schema.json
index 2fc1a27..1346bcc 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -264,6 +264,29 @@
            '*format': 'DataFormat'} }
 
 ##
+# @memchar-read:
+#
+# Provide read interface for memchardev. Read from memchar
+# char device and return the data.
+#
+# @chardev: the name of the  memchar char device.
+#
+# @size: the size to write in bytes.
+#
+# @format: #optional the format of the data want to read from
+#          memchardev, by default is 'utf8'.
+#
+# Returns: The data read from memchar as string.
+#          If @chardev is not a valid memchr device, DeviceNotFound
+#          If an I/O error occurs while reading, IOError
+#
+# Since: 1.2
+##
+{ 'command': 'memchar-read',
+  'data': {'chardev': 'str', 'size': 'int', '*format': 'DataFormat'},
+  'returns': 'str' }
+
+##
 # @CommandInfo:
 #
 # Information about a QMP command
diff --git a/qemu-char.c b/qemu-char.c
index d8f3238..ff6651b 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2683,6 +2683,38 @@ void qmp_memchar_write(const char *chardev, int64_t size,
 
 }
 
+char *qmp_memchar_read(const char *chardev, int64_t size,
+                       bool has_format, enum DataFormat format,
+                       Error **errp)
+
+{
+    CharDriverState *chr;
+    guchar *read_data;
+    char * data = NULL;
+
+    read_data = g_malloc0(size);
+
+    chr = qemu_chr_find(chardev);
+    if(!chr) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, chardev);
+        return NULL;
+    }
+
+    mem_chr_read(chr, read_data, size);
+
+    if (has_format) {
+        if (format == DATA_FORMAT_BASE64) {
+            data = g_base64_encode(read_data, (size_t)size);
+        }
+    } else {
+        data = (char *)read_data;
+    }
+
+    g_free(read_data);
+
+    return data;
+}
+
 QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename)
 {
     char host[65], port[33], width[8], height[8];
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 3c747cd..a9890db 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -474,6 +474,37 @@ Example:
 EQMP
 
     {
+        .name       = "memchar-read",
+        .args_type  = "chardev:s,size:i",
+        .mhandler.cmd_new = qmp_marshal_input_memchar_read,
+    },
+
+SQMP
+memchar-read
+-------------
+
+Provide read interface for memchardev. Read from memchar
+char device and return the data.
+
+Arguments:
+
+- "chardev": the name of the char device, must be unique (json-string)
+- "size": the memory size in bytes, init size of the memchar
+          by default (json-int)
+- "format": the data format want to read from mechardev.
+  (DataFormat, optional, support "utf8" and "base64" now, default "utf8")
+
+Example:
+
+-> { "execute": "memchar-read",
+                "arguments": { "chardev": foo,
+                               "size": 1000,
+                               "format": "utf8" }
+<- { "return": "data string..." }
+
+EQMP
+
+    {
         .name       = "xen-save-devices-state",
         .args_type  = "filename:F",
     .mhandler.cmd_new = qmp_marshal_input_xen_save_devices_state,
-- 
1.7.7.6