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Re: [Qemu-devel] [PATCH v3 1/4] util - add automated ID generation utili
From: |
Programmingkid |
Subject: |
Re: [Qemu-devel] [PATCH v3 1/4] util - add automated ID generation utility |
Date: |
Tue, 13 Oct 2015 15:25:04 -0400 |
On Oct 13, 2015, at 11:26 AM, Markus Armbruster wrote:
> Jeff Cody <address@hidden> writes:
>
>> On Tue, Oct 13, 2015 at 09:37:29AM +0200, Markus Armbruster wrote:
>>> Jeff Cody <address@hidden> writes:
>>>
>>>> Multiple sub-systems in QEMU may find it useful to generate IDs
>>>> for objects that a user may reference via QMP or HMP. This patch
>>>> presents a standardized way to do it, so that automatic ID generation
>>>> follows the same rules.
>>>>
>>>> This patch enforces the following rules when generating an ID:
>>>>
>>>> 1.) Guarantee no collisions with a user-specified ID
>>>> 2.) Identify the sub-system the ID belongs to
>>>> 3.) Guarantee of uniqueness
>>>> 4.) Spoiling predictability, to avoid creating an assumption
>>>> of object ordering and parsing (i.e., we don't want users to think
>>>> they can guess the next ID based on prior behavior).
>>>>
>>>> The scheme for this is as follows (no spaces):
>>>>
>>>> # subsys D RR
>>>> Reserved char --| | | |
>>>> Subsystem String ----| | |
>>>> Unique number (64-bit) --| |
>>>> Two-digit random number ---|
>>>>
>>>> For example, a generated node-name for the block sub-system may look
>>>> like this:
>>>>
>>>> #block076
>>>>
>>>> The caller of id_generate() is responsible for freeing the generated
>>>> node name string with g_free().
>>>>
>>>> Reviewed-by: John Snow <address@hidden>
>>>> Reviewed-by: Eric Blake <address@hidden>
>>>> Reviewed-by: Alberto Garcia <address@hidden>
>>>> Signed-off-by: Jeff Cody <address@hidden>
>>>> ---
>>>> include/qemu-common.h | 8 ++++++++
>>>> util/id.c | 37 +++++++++++++++++++++++++++++++++++++
>>>> 2 files changed, 45 insertions(+)
>>>>
>>>> diff --git a/include/qemu-common.h b/include/qemu-common.h
>>>> index 0bd212b..2f74540 100644
>>>> --- a/include/qemu-common.h
>>>> +++ b/include/qemu-common.h
>>>> @@ -246,6 +246,14 @@ int64_t qemu_strtosz_suffix_unit(const char *nptr,
>>>> char **end,
>>>> #define STR_OR_NULL(str) ((str) ? (str) : "null")
>>>>
>>>> /* id.c */
>>>> +
>>>> +typedef enum IdSubSystems {
>>>> + ID_QDEV,
>>>
>>> ID_QDEV is not used in this series. Do you intend to use it in a
>>> followup-series? Can we reasonably expect that series will be accepted?
>>>
>>
>> John Arbuckle has a patch on list that uses it. I haven't reviewed
>> it, however - but I guess it depends ultimately on whether qdev will
>> allow autogeneration for its IDs or not.
>
> Then that patch should add ID_QDEV.
>
>>> You could sidestep these questions by making id_generate() take a string
>>> argument ;)
>>>
>>
>> I'd rather avoid having each system specifying a string inline in
>> their code. It is cleaner to have the strings defined in a central
>> location, I think (not to mention, easier to reference).
I can see the benefit of using a string. The id_generate() function
could use va_args like printf() uses to allow almost any kind of
string argument. An empty string argument could mean to default to
ID_MAX. But I also think using an enumeration is good enough, so
either way is good.
[Qemu-devel] [PATCH v3 3/4] block: add filter for generated node-names, Jeff Cody, 2015/10/12
[Qemu-devel] [PATCH v3 2/4] block: auto-generated node-names, Jeff Cody, 2015/10/12
[Qemu-devel] [PATCH v3 4/4] qemu-iotests: update tests for generated node-names, Jeff Cody, 2015/10/12
Re: [Qemu-devel] [PATCH v3 0/4], Kevin Wolf, 2015/10/13