Re: [Qemu-devel] [PATCH 1/2] qga: add guest-get-time command

[Eric Blake]

On 01/27/2013 11:14 AM, Lei Li wrote:
> Signed-off-by: Lei Li <address@hidden>
> ---
>  include/qapi/qmp/qerror.h |    3 +++
>  qga/commands-posix.c      |   30 ++++++++++++++++++++++++++++++
>  qga/qapi-schema.json      |   38 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 71 insertions(+), 0 deletions(-)
> 
> diff --git a/include/qapi/qmp/qerror.h b/include/qapi/qmp/qerror.h
> index 6c0a18d..0baf1a4 100644
> --- a/include/qapi/qmp/qerror.h
> +++ b/include/qapi/qmp/qerror.h
> @@ -129,6 +129,9 @@ void assert_no_error(Error *err);
>  #define QERR_FEATURE_DISABLED \
>      ERROR_CLASS_GENERIC_ERROR, "The feature '%s' is not enabled"
>  
> +#define QERR_GET_TIME_FAILED \
> +    ERROR_CLASS_GENERIC_ERROR, "Failed to get time"
> +

These days, you shouldn't be defining a new QERR wrapper.  Instead,...[1]

>  
> +static TimeInfo *get_host_time(Error **errp)

This name is unusual...[2]

> +{
> +    int ret;
> +    qemu_timeval tq;
> +    TimeInfo *time_info;
> +
> +    ret = qemu_gettimeofday(&tq);
> +    if (ret < 0) {
> +        error_set_errno(errp, errno, QERR_GET_TIME_FAILED);

[1]...use the right idiom here:

error_setg_errno(errp, errno, "Failed to get time");

> +        return NULL;
> +    }
> +
> +    time_info = g_malloc0(sizeof(TimeInfo));
> +    time_info->seconds = tq.tv_sec;
> +    time_info->microseconds = tq.tv_usec;

Is microseconds the right unit to expose through JSON, or are we going
to wish we had exposed nanoseconds down the road (you can still use
qemu_gettimeofday() and scale tv_usec by 1000 before assigning to
time_info->nanoseconds, if we desire the extra granularity).

You aren't setting time_info->utc_offset.  Is that intentional?

> +
> +    return time_info;
> +}
> +
> +struct TimeInfo *qmp_guest_get_time(Error **errp)
> +{
> +    TimeInfo *time_info = get_host_time(errp);

[2]...given that it is only ever called from qmp_guest_get_time.

> +
> +    if (!time_info) {
> +        return NULL;
> +    }

These three lines can be deleted,

> +
> +    return time_info;

since this line will do the same thing if you let NULL time_info get
this far.

> +++ b/qga/qapi-schema.json
> @@ -83,6 +83,44 @@
>  { 'command': 'guest-ping' }
>  
>  ##
> +# @TimeInfo
> +#
> +# Time Information. It is relative to the Epoch of 1970-01-01.
> +#
> +# @seconds: "seconds" time unit.
> +#
> +# @microseconds: "microseconds" time unit.
> +#
> +# @utc-offset: Information about utc offset. Represented as:
> +#              ±[mmmm] based at a minimum on minutes, with

s/based at a minimum on//

This still doesn't state whether two hours east of UTC is represented as
120 or as 0200.

> +#              negative values are west and positive values
> +#              are east of UTC. The bounds of @utc-offset is
> +#              at most 24 hours away from UTC.
> +#
> +# Since: 1.4
> +##
> +{ 'type': 'TimeInfo',
> +  'data': { 'seconds': 'int', 'microseconds': 'int',
> +            'utc-offset': 'int' } }
> +
> +##
> +# @guest-get-time:
> +#
> +# Get the information about host time in UTC and the

s/host/guest/

> +# UTC offset.
> +#
> +# This command tries to get the host time which is
> +# presumably correct, since we need to be able to
> +# resynchronize guest clock to host's in guest.

This sentence doesn't make sense.  Better would be:

Get the guest's notion of the current time.

> +#
> +# Returns: @TimeInfo on success.
> +#
> +# Since 1.4
> +##
> +{ 'command': 'guest-get-time',
> +  'returns': 'TimeInfo' }
> +
> +##
>  # @GuestAgentCommandInfo:
>  #
>  # Information about guest agent commands.
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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