qemu-char: Saner naming of memchar stuff & doc fixes

New device, has never been released, so we can still improve things
without worrying about compatibility.

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.  Therefore:

* Rename CirMemCharDriver to RingBufCharDriver, and call the thing a
  "ringbuf" in the API.

* Rename QMP and HMP commands from memchar-FOO to ringbuf-FOO.

* Rename device parameter from maxcapacity to size (simple words are
  good for you).

* Clearly mark the parameter as optional in documentation.

* Fix error reporting so that chardev-add reports to current monitor,
  not stderr.

* Replace cirmem in C identifiers by ringbuf.

* Rework documentation.  Document the impact of our crappy UTF-8
  handling on reading.

* QMP examples that even work.

I could split this up into multiple commits, but they'd change the
same documentation lines multiple times.  Not worth it.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 17 insertions, 20 deletions

diff --git a/hmp-commands.hx b/hmp-commands.hx
index bdd48f3469..66ec716e03 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -841,40 +841,37 @@ Inject an NMI on the given CPU (x86 only).
 ETEXI
 
     {
-        .name       = "memchar_write",
+        .name       = "ringbuf_write",
         .args_type  = "device:s,data:s",
         .params     = "device data",
-        .help       = "Provide writing interface for CirMemCharDriver. Write"
-                      "'data' to it.",
-        .mhandler.cmd = hmp_memchar_write,
+        .help       = "Write to a ring buffer character device",
+        .mhandler.cmd = hmp_ringbuf_write,
     },
 
 STEXI
-@item memchar_write @var{device} @var{data}
-@findex memchar_write
-Provide writing interface for CirMemCharDriver. Write @var{data}
-to char device 'memory'.
+@item ringbuf_write @var{device} @var{data}
+@findex ringbuf_write
+Write @var{data} to ring buffer character device @var{device}.
+@var{data} must be a UTF-8 string.
 
 ETEXI
 
     {
-        .name       = "memchar_read",
+        .name       = "ringbuf_read",
         .args_type  = "device:s,size:i",
         .params     = "device size",
-        .help       = "Provide read interface for CirMemCharDriver. Read from"
-                      "it and return the data with size.",
-        .mhandler.cmd = hmp_memchar_read,
+        .help       = "Read from a ring buffer character device",
+        .mhandler.cmd = hmp_ringbuf_read,
     },
 
 STEXI
-@item memchar_read @var{device}
-@findex memchar_read
-Provide read interface for CirMemCharDriver. Read from char device
-'memory' and return the data.
-
-@var{size} is the size of data want to read from. 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.
+@item ringbuf_read @var{device}
+@findex ringbuf_read
+Read and print up to @var{size} bytes from ring buffer character
+device @var{device}.
+Bug: can screw up when the buffer contains invalid UTF-8 sequences,
+NUL characters, after the ring buffer lost data, and when reading
+stops because the size limit is reached.
 
 ETEXI