Re: [PATCH v5 05/14] tools/libxc: unused attribute in DECLARE_HYPERCALL_BUFFER_SHADOW

[Yang Hongyang <yanghy@cn.fujitsu.com>]

On 05/13/2015 11:57 PM, Ian Campbell wrote:
> On Wed, 2015-05-13 at 09:53 +0800, Yang Hongyang wrote:
>> There are cases that we only need to use the hypercall buffer data,
>
> "cases where"
>> and do not use the xc_hypercall_buffer_t struct.
>> DECLARE_HYPERCALL_BUFFER_SHADOW define a user pointer that can allow
>
> "defines a user pointer"
>
>> us to access the hypercall buffer data but it also define a
>
> "defines"
>
>> xc_hypercall_buffer_t that we don't use, the compiler will report arg
>> unused error.
>> add __attribute__((unused)) before xc_hypercall_buffer_t to avoid
>> the compiler error.
>>
>> The cases for example:
>
> "Example cases:"
>
>> In send_all_pages(), we only need to use the haypercall buffer data
>
> "hypercall"
>
>> which is a dirty bitmap, we set the dirty bitmap to all dirty and call
>> send_dirty_pages, we will not use the xc_hypercall_buffer_t and hypercall
>> to retrive the dirty bitmap.
>
> "retrieve"
>
>> In send_some_pages(), we will also only need to use the dirty_bitmap.
>> the retrive dirty bitmap hypercall are done by the caller.
>
> and again.
>
>>
>> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
>> CC: Ian Campbell <Ian.Campbell@citrix.com>
>> CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
>> CC: Wei Liu <wei.liu2@citrix.com>
>> CC: Andrew Cooper <andrew.cooper3@citrix.com>
>> ---
>>   tools/libxc/include/xenctrl.h | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
>> index a689caf..0804257 100644
>> --- a/tools/libxc/include/xenctrl.h
>> +++ b/tools/libxc/include/xenctrl.h
>> @@ -284,11 +284,15 @@ typedef struct xc_hypercall_buffer xc_hypercall_buffer_t;
>>    * Useful when a hypercall buffer is passed to a function and access
>>    * via the user pointer is required.
>>    *
>> + * The shadow xc_hypercall_buffer_t may be unused, add
>> + * __attribute__((unused)) to avoid compiler error.
>
> No need for this comment IMHO.
>
>>    * See DECLARE_HYPERCALL_BUFFER_ARGUMENT() if the user pointer is not
>>    * required.
>>    */
>>   #define DECLARE_HYPERCALL_BUFFER_SHADOW(_type, _name, _hbuf)   \
>>       _type *(_name) = (_hbuf)->hbuf;                            \
>> +    __attribute__((unused))                                    \
>
> This is a somewhat unconventional location for such a tagm but putting
> it elsewhere would involve faff-some rewrapping.
>
> So apart from the typos looks good.

Will fix those typos, thank you!

>
>
>>       xc_hypercall_buffer_t XC__HYPERCALL_BUFFER_NAME(_name) = { \
>>           .hbuf = (void *)-1,                                    \
>>           .param_shadow = (_hbuf),                               \
>
>
> .
>

-- 
Thanks,
Yang.