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Re: [Qemu-devel] [PATCH 2/4] Revert "chardev: Make the name of memory de

From: Lei Li
Subject: Re: [Qemu-devel] [PATCH 2/4] Revert "chardev: Make the name of memory device consistent"
Date: Fri, 28 Jun 2013 11:35:18 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0

On 06/27/2013 10:22 PM, Markus Armbruster wrote:
This reverts commit 6a85e60cb994bd95d1537aafbff65816f3de4637.

Commit 51767e7 "qemu-char: Add new char backend CirMemCharDriver"
introduced a memory ring buffer character device driver named
"memory".  Commit 3949e59 "qemu-char: Saner naming of memchar stuff &
doc fixes" changed the driver name to "ringbuf", along with a whole
bunch of other names, with the following rationale:

     Naming is a mess.  The code calls the device driver
     CirMemCharDriver, the public API calls it "memory", "memchardev",
     or "memchar", and the special commands are named like
     "memchar-FOO".  "memory" is a particularly unfortunate choice,
     because there's another character device driver called
     MemoryDriver.  Moreover, the device's distinctive property is that
     it's a ring buffer, not that's in memory.

This is what we released in 1.4.0.

Unfortunately, the rename missed a critical instance of "memory": the
actual driver name.  Thus, the new device could be used only by an
entirely undocumented name.  The documented name did not work.

Hi Markus.

Actually I fixed this issue as the your coming patch set 3&4 (make them
consistent with 'ringbuf') in the beginning, but according to Paolo's
comments, since '-chardev memory' exists in 1.4 and cannot be renamed,
so made such change as Commit 6a85e60cb994bd95d1537aafbff65816f3de4637.

The original patch and discussion as link below:


Commit 6a85e60 fixes this by changing the documentation to match the
code.  It also changes some, but not all related occurences of
"ringbuf" to "memory".  Left alone are identifiers in C code, HMP and
QMP commands.  The latter are external interface, so they can't be

The result is an inconsistent mess.  Moreover, "memory" is a rotten
name.  The device's distinctive property is that it's a ring buffer,
not that's in memory.  User's don't care whether it's in RAM, flash,
or carved into chocolate tablets by Oompa Loompas.

Revert the commit.  Next commit will fix just the bug.

Cc: address@hidden
Signed-off-by: Markus Armbruster <address@hidden>
  qapi-schema.json |  6 +++---
  qemu-char.c      | 16 ++++++++--------
  qemu-options.hx  |  6 +++---
  3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/qapi-schema.json b/qapi-schema.json
index 6cc07c2..6445da6 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3275,7 +3275,7 @@
                                   '*rows'   : 'int' } }

-# @ChardevMemory:
+# @ChardevRingbuf:
  # Configuration info for memory chardevs
@@ -3283,7 +3283,7 @@
  # Since: 1.5
-{ 'type': 'ChardevMemory', 'data': { '*size'  : 'int' } }
+{ 'type': 'ChardevRingbuf', 'data': { '*size'  : 'int' } }

  # @ChardevBackend:
@@ -3310,7 +3310,7 @@
                                         'spicevmc' : 'ChardevSpiceChannel',
                                         'spiceport' : 'ChardevSpicePort',
                                         'vc'     : 'ChardevVC',
-                                       'memory' : 'ChardevMemory' } }
+                                       'memory' : 'ChardevRingbuf' } }

  # @ChardevReturn:
diff --git a/qemu-char.c b/qemu-char.c
index 63a9221..a8fad65 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2786,8 +2786,8 @@ static void ringbuf_chr_close(struct CharDriverState *chr)
      chr->opaque = NULL;

-static CharDriverState *qemu_chr_open_memory(ChardevMemory *opts,
-                                             Error **errp)
+static CharDriverState *qemu_chr_open_ringbuf(ChardevRingbuf *opts,
+                                              Error **errp)
      CharDriverState *chr;
      RingBufCharDriver *d;
@@ -2799,7 +2799,7 @@ static CharDriverState 
*qemu_chr_open_memory(ChardevMemory *opts,

      /* The size must be power of 2 */
      if (d->size & (d->size - 1)) {
-        error_setg(errp, "size of memory chardev must be power of two");
+        error_setg(errp, "size of ringbuf chardev must be power of two");
          goto fail;

@@ -3101,12 +3101,12 @@ static void qemu_chr_parse_pipe(QemuOpts *opts, 
ChardevBackend *backend,
      backend->pipe->device = g_strdup(device);

-static void qemu_chr_parse_memory(QemuOpts *opts, ChardevBackend *backend,
-                                  Error **errp)
+static void qemu_chr_parse_ringbuf(QemuOpts *opts, ChardevBackend *backend,
+                                   Error **errp)
      int val;

-    backend->memory = g_new0(ChardevMemory, 1);
+    backend->memory = g_new0(ChardevRingbuf, 1);

      val = qemu_opt_get_size(opts, "size", 0);
      if (val != 0) {
@@ -3705,7 +3705,7 @@ ChardevReturn *qmp_chardev_add(const char *id, 
ChardevBackend *backend,
          chr = vc_init(backend->vc);
-        chr = qemu_chr_open_memory(backend->memory, errp);
+        chr = qemu_chr_open_ringbuf(backend->memory, errp);
          error_setg(errp, "unknown chardev backend (%d)", backend->kind);
@@ -3756,7 +3756,7 @@ static void register_types(void)
      register_char_driver("socket", qemu_chr_open_socket);
      register_char_driver("udp", qemu_chr_open_udp);
      register_char_driver_qapi("memory", CHARDEV_BACKEND_KIND_MEMORY,
-                              qemu_chr_parse_memory);
+                              qemu_chr_parse_ringbuf);
      register_char_driver_qapi("file", CHARDEV_BACKEND_KIND_FILE,
      register_char_driver_qapi("stdio", CHARDEV_BACKEND_KIND_STDIO,
diff --git a/qemu-options.hx b/qemu-options.hx
index ca6fdf6..3b71e39 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1781,7 +1781,7 @@ DEF("chardev", HAS_ARG, QEMU_OPTION_chardev,
      "-chardev msmouse,id=id[,mux=on|off]\n"
      "         [,mux=on|off]\n"
-    "-chardev memory,id=id[,size=size]\n"
+    "-chardev ringbuf,id=id[,size=size]\n"
      "-chardev file,id=id,path=path[,mux=on|off]\n"
      "-chardev pipe,id=id,path=path[,mux=on|off]\n"
  #ifdef _WIN32
@@ -1819,7 +1819,7 @@ Backend is one of:
@@ -1928,7 +1928,7 @@ the console, in pixels.
  @option{cols} and @option{rows} specify that the console be sized to fit a 
  console with the given dimensions.

address@hidden -chardev memory ,address@hidden [,address@hidden
address@hidden -chardev ringbuf ,address@hidden [,address@hidden

  Create a ring buffer with fixed size @option{size}.
  @var{size} must be a power of two, and defaults to @code{64K}).


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