Re: [RFC Patch v3 16/18] update libxl__device_disk_from_xs_be() to support blktap device

[Wen Congyang <wency@cn.fujitsu.com>]

On 09/12/2014 04:53 PM, Wei Liu wrote:
> On Thu, Sep 11, 2014 at 03:58:37PM +0800, Wen Congyang wrote:
>> On 09/08/2014 07:42 PM, Ian Campbell wrote:
>>> On Fri, 2014-09-05 at 17:10 +0800, Wen Congyang wrote:
>>>>
>>>> +int libxl_string_to_format(libxl_ctx *ctx, char *s, libxl_disk_format
>>>> *format)
>>>> +{
>>>
>>> This already exists as libxl_disk_format_to_string.
>>
>> Another question:
>> We store format:file to tapdisk-params/params. But we store aio if the format
>> is raw. libxl_disk_format_to_string() doesn't recognize aio...
>>
> 
> I think you're talking about libxl_disk_format_from_string...

Yes

> 
> FWIW, have you looked at libxl__device_disk_string_of_format?

char *libxl__device_disk_string_of_format(libxl_disk_format format)
{
    switch (format) {
        case LIBXL_DISK_FORMAT_QCOW: return "qcow";
        case LIBXL_DISK_FORMAT_QCOW2: return "qcow2";
        case LIBXL_DISK_FORMAT_VHD: return "vhd";
        case LIBXL_DISK_FORMAT_RAW:
        case LIBXL_DISK_FORMAT_EMPTY: return "aio";
        default: return NULL;
    }
}

If the format is LIBXL_DISK_FORMAT_RAW, we store "aio" in tapdisk-params/params,
But libxl_disk_format_from_string():
libxl_enum_string_table libxl_disk_format_string_table[] = {
    { .s = "unknown", .v = LIBXL_DISK_FORMAT_UNKNOWN },
    { .s = "qcow", .v = LIBXL_DISK_FORMAT_QCOW },
    { .s = "qcow2", .v = LIBXL_DISK_FORMAT_QCOW2 },
    { .s = "vhd", .v = LIBXL_DISK_FORMAT_VHD },
    { .s = "raw", .v = LIBXL_DISK_FORMAT_RAW },
    { .s = "empty", .v = LIBXL_DISK_FORMAT_EMPTY },
    { NULL, -1 },
};

int libxl_disk_format_from_string(const char *s, libxl_disk_format *e)
{
    return libxl__enum_from_string(libxl_disk_format_string_table,
                                   s, (int *)e);
}
If the string is "aio", libxl_disk_format_from_string() will return ERROR_FAIL.

We have two choices:
1. Introduce a new API
2. store "raw" in tapdisk-params/params

Thanks
Wen Congyang

> 
> Wei.
> 
>> Is it ok to change the value stored in tapdisk-params/params?
>>
>> Thanks
>> Wen Congyang
>>
>>>
>>> Ian.
>>>
>>> .
>>>
>>
>>
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> .
>