[Qemu-devel] [PATCH 4/5] 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  |   25 +++++++++++++++++++++++++
 hmp.c            |   17 +++++++++++++++++
 hmp.h            |    1 +
 qapi-schema.json |   27 +++++++++++++++++++++++++++
 qemu-char.c      |   52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 qmp-commands.hx  |   40 ++++++++++++++++++++++++++++++++++++++++
 6 files changed, 162 insertions(+), 0 deletions(-)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index 753aab3..5f91428 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -847,6 +847,31 @@ that specifies behavior when the queue is full/empty. By default is
 ETEXI
 
     {
+        .name       = "memchar_read",
+        .args_type  = "chardev:s,control:-b,size:i",
+        .params     = "chardev [-b] size",
+        .help       = "Provide read interface for CirMemCharDriver. Read from"
+                      "it and return 'size' of the data. (Use -b for 'block'"
+                      "option)",
+        .mhandler.cmd = hmp_memchar_read,
+    },
+
+STEXI
+@item memchar_read [-b] @var{chardev}
+@findex memchar_read
+Provide read interface for CirMemCharDriver. Read from cirmemchr
+char device and return @var{size} of the data.
+
+@var{size} is the size of data want to read from.
+
+@var{control} is option['block', 'drop'] for read and write command
+that specifies behavior when the queue is full/empty. By default is
+'drop'. Note that the 'block' option is not supported now.
+        -b for 'block' option. None for 'drop' option.
+
+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 18ca61b..fa858c4 100644
--- a/hmp.c
+++ b/hmp.c
@@ -690,6 +690,23 @@ 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;
+    enum DataFormat format;
+    int con = qdict_get_try_bool(qdict, "block", 0);
+    enum CongestionControl control;
+    Error *errp = NULL;
+
+    format = DATA_FORMAT_UTF8;
+    control = con ? CONGESTION_CONTROL_BLOCK : CONGESTION_CONTROL_DROP;
+    data = qmp_memchar_read(chardev, size, true, format,
+                            true, control, &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 406ebb1..a5a0cfe 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 a908aa6..4db91b0 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -394,6 +394,33 @@
            '*control': 'CongestionControl'} }
 
 ##
+# @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 read in bytes.
+#
+# @format: #optional the format of the data want to read from
+#          memchardev, by default is 'utf8'.
+#
+# @control: #optional options for read and write command that specifies
+#           behavior when the queue is full/empty.
+#
+# 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: 1.3
+##
+{ 'command': 'memchar-read',
+  'data': {'chardev': 'str', 'size': 'int', '*format': 'DataFormat',
+           '*control': 'CongestionControl'},
+  'returns': 'str' }
+
+##
 # @CommandInfo:
 #
 # Information about a QMP command
diff --git a/qemu-char.c b/qemu-char.c
index 133d282..a8bcead 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2736,6 +2736,58 @@ 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,
+                       bool has_control, enum CongestionControl control,
+                       Error **errp)
+{
+    CharDriverState *chr;
+    guchar *read_data;
+    char *data = NULL;
+    int ret;
+
+    read_data = g_malloc0(size);
+
+    chr = qemu_chr_find(chardev);
+    if (!chr) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, chardev);
+        return NULL;
+    }
+
+    /* XXX: For the sync command as 'block', waiting for the qmp
+ *      * to support necessary feature. Now just act as 'drop'. */
+    if (cirmem_chr_is_empty(chr)) {
+        if (has_control && (control == CONGESTION_CONTROL_BLOCK)) {
+            error_setg(errp, "Failed to read from memchr %s", chardev);
+            return NULL;
+        } else {
+            error_setg(errp, "Failed to read from memchr %s", chardev);
+            return NULL;
+        }
+    }
+
+    if (size == 0) {
+        size = CBUFF_SIZE;
+    }
+
+    ret = cirmem_chr_read(chr, read_data, size);
+
+    if (ret < 0) {
+        error_setg(errp, "Failed to read from memchr %s", chardev);
+        return NULL;
+    }
+
+    if (has_format && (format == DATA_FORMAT_BASE64)) {
+       if (read_data) {
+           data = g_base64_encode(read_data, (size_t)size);
+       }
+    } else {
+        data = (char *)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 502ed57..08ea798 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -506,6 +506,46 @@ Example:
 EQMP
 
     {
+        .name       = "memchar-read",
+        .args_type  = "chardev:s,size:i,format:s?,control:s?",
+        .help       = "return the size of data from memchar chardev",
+        .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 wanted to read in bytes(refer to unencoded
+          size of the raw data), would adjust to the init size of the
+          memchar if the requested size is larger than it. (json-int)
+- "format": the data format write to memchardev, default is
+            utf8. (json-string, optional)
+          - Possible values: "utf8", "base64"
+
+- "control": options for read and write command that specifies
+             behavior when the queue is full/empty, default is
+             drop. (json-string, optional)
+          - Possible values: "drop", "block"
+
+Example:
+
+-> { "execute": "memchar-read",
+                "arguments": { "chardev": foo,
+                               "size": 1000,
+                               "format": "utf8",
+                               "control": "drop" } }
+<- { "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