Re: [Qemu-devel] [PATCH 1/3] vmstate: introduce calc_size VMStateField

[Peter Maydell]

On 26 December 2011 10:03, Mitsyanko Igor <address@hidden> wrote:
> New calc_size field in VMStateField is supposed to help us easily add 
> save/restore
> support of dynamically allocated buffers in device's states.
> There are some cases when information on size of dynamically allocated buffer 
> is
> already presented in specific device's state structure, but in such a form, 
> that
> can not be used with existing VMStateField interface. Currently, we either 
> can get size from
> another variable in device's state as it is with VMSTATE_VBUFFER_* macros, or 
> we can
> also multiply value kept in a variable by a constant with 
> VMSTATE_BUFFER_MULTIPLY
> macro. If we need to perform any other action, we're forced to add additional
> variable with size information to device state structure with the only 
> intention
> to use it in VMStateDescription structure. This approach is not very pretty. 
> Adding extra
> flags to VMStateFlags enum for every other possible operation with size field
> seems redundant, and still it would't cover cases when we need to perform a 
> set of
> operations to get size value.
> With this new .calc_size field we can calculate size of dynamic array in 
> whichever
> way we need.
>
> Signed-off-by: Mitsyanko Igor <address@hidden>

It seems a bit curious that this patch removes the existing (although admittedly
unused) VMSTATE_BUFFER_MULTIPLY but doesn't actually say so in the
commit message.

> ---
>  hw/hw.h  |   14 +++++++-------
>  savevm.c |   14 ++++++++------
>  2 files changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/hw/hw.h b/hw/hw.h
> index efa04d1..8ce4475 100644
> --- a/hw/hw.h
> +++ b/hw/hw.h
> @@ -303,9 +303,9 @@ enum VMStateFlags {
>     VMS_ARRAY_OF_POINTER = 0x040,
>     VMS_VARRAY_UINT16    = 0x080,  /* Array with size in uint16_t field */
>     VMS_VBUFFER          = 0x100,  /* Buffer with size in int32_t field */
> -    VMS_MULTIPLY         = 0x200,  /* multiply "size" field by field_size */
> -    VMS_VARRAY_UINT8     = 0x400,  /* Array with size in uint8_t field*/
> -    VMS_VARRAY_UINT32    = 0x800,  /* Array with size in uint32_t field*/
> +    VMS_CALC_SIZE        = 0x200,  /* calculate size of dynamic buffer */
> +    VMS_VARRAY_UINT8     = 0x400,  /* Array with size in uint8_t field */
> +    VMS_VARRAY_UINT32    = 0x800,  /* Array with size in uint32_t field */

These unrelated whitespace fixes are confusing -- please drop them.

-- PMM