[3/3] QAPI: Introduce memchar-read QMP command

Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
---
 hmp-commands.hx  |   19 ++++++++++++++++++
 hmp.c            |   17 ++++++++++++++++
 hmp.h            |    1 +
 qapi-schema.json |   25 +++++++++++++++++++++++
 qemu-char.c      |   57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 qmp-commands.hx  |   34 ++++++++++++++++++++++++++++++++
 6 files changed, 153 insertions(+), 0 deletions(-)

On Tue, 22 Jan 2013 16:12:52 +0800
Lei Li <lilei@linux.vnet.ibm.com> wrote:

> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
> ---
>  hmp-commands.hx  |   19 ++++++++++++++++++
>  hmp.c            |   17 ++++++++++++++++
>  hmp.h            |    1 +
>  qapi-schema.json |   25 +++++++++++++++++++++++
>  qemu-char.c      |   57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  qmp-commands.hx  |   34 ++++++++++++++++++++++++++++++++
>  6 files changed, 153 insertions(+), 0 deletions(-)
> 
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index e546c76..52ead10 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -856,6 +856,25 @@ to char device 'memory'.
>  ETEXI
>  
>      {
> +        .name       = "memchar_read",
> +        .args_type  = "chardev:s,size:i",
> +        .params     = "chardev size",

Also missing .help.

> +        .mhandler.cmd = hmp_memchar_read,
> +    },
> +
> +STEXI
> +@item memchar_read @var{chardev}
> +@findex memchar_read
> +Provide read interface for CirMemCharDriver. Read from char device
> +'memory' and return @var{size} of 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.
> +
> +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 546d687..7e86c24 100644
> --- a/hmp.c
> +++ b/hmp.c
> @@ -697,6 +697,23 @@ 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;
> +    Error *errp = NULL;
> +
> +    data = qmp_memchar_read(chardev, size, false, 0, &errp);
> +    if (errp) {
> +        monitor_printf(mon, "%s\n", error_get_pretty(errp));
> +        error_free(errp);
> +        return;
> +    }
> +
> +    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 06d6ea2..076d8cf 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 c34e9ac..56d4b39 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -366,6 +366,31 @@
>             '*format': 'DataFormat'} }
>  
>  ##
> +# @memchar-read:
> +#
> +# Provide read interface for memchardev. Read from the char
> +# device 'memory' and return the data.
> +#
> +# @chardev: the name of the memory 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'.
> +#
> +# Returns: The data read from memchar as string

I think you also have to return the number of bytes read. Please, take
a look at the guest-file-read command in qga/qapi-schema.json.

> +#          If @chardev is not a valid memchr device, DeviceNotFound
> +#
> +# Notes: For now assume 'drop' behaver, which would result in reads
> +#        returning empty strings.

Please, drop that note. It's not needed and actually it contradicts the
code.

> +#
> +# Since: 1.4
> +##
> +{ '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 c3bb6ec..a1fb543 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -2802,6 +2802,63 @@ 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;
> +    int ret;
> +    size_t count;
> +
> +    chr = qemu_chr_find(chardev);
> +    if (!chr) {
> +        error_set(errp, QERR_DEVICE_NOT_FOUND, chardev);
> +        return NULL;
> +    }
> +
> +    if (qemu_is_chr(chr, "memory")) {
> +        error_setg(errp,"%s is not memory char device\n", chardev);
> +        return NULL;
> +    }
> +
> +    if (size <= 0) {
> +        error_setg(errp, "Failed to read from device %s", chardev);

Bad error message. Please, write something like 'size must be greater than zero'

> +        return NULL;
> +    }
> +
> +    /* XXX: Return the empty strings when the buffer is empty. */
> +    if (cirmem_chr_is_empty(chr)) {
> +        error_setg(errp, "Memory device %s is empty", chardev);
> +        return NULL;
> +    }

Why don't you return an empty string then? I don't think we should or
even can do it later.

> +
> +    count = qemu_chr_cirmem_count(chr);
> +    size = size > count ? count : size;
> +    read_data = g_malloc0(size + 1);
> +
> +    ret = cirmem_chr_read(chr, read_data, size);
> +    if (ret < size) {
> +        error_setg(errp, "Failed to read from device %s", chardev);
> +        goto fail;
> +    }
> +
> +    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;
> +
> +fail:
> +    g_free(read_data);
> +    return NULL;
> +}
> +
>  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 8ad06d0..53a8f4d 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -500,6 +500,40 @@ Example:
>  EQMP
>  
>      {
> +        .name       = "memchar-read",
> +        .args_type  = "chardev:s,size:i,format:s?",
> +        .help       = "return the size of data from memchar chardev",

Please, drop .help. It's only needed for hmp commands.

> +        .mhandler.cmd_new = qmp_marshal_input_memchar_read,
> +    },
> +
> +SQMP
> +memchar-read
> +-------------
> +
> +Provide read interface for CirMemCharDriver. Read from the char
> +device memory 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"
> +
> +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,