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Re: [Qemu-devel] Re: [PATCH 07/11] eeprom93xx: Use the new hack macro to

From: Anthony Liguori
Subject: Re: [Qemu-devel] Re: [PATCH 07/11] eeprom93xx: Use the new hack macro to avoid duplicate field names
Date: Wed, 23 Mar 2011 07:34:00 -0500
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On 03/23/2011 04:58 AM, Juan Quintela wrote:
Anthony Liguori<address@hidden>  wrote:
I don't fully understand this hack business but we need field to be unique so..

Signed-off-by: Anthony Liguori<address@hidden>
  hw/eeprom93xx.c |    2 +-
  1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/hw/eeprom93xx.c b/hw/eeprom93xx.c
index cfa695d..f1d75ec 100644
--- a/hw/eeprom93xx.c
+++ b/hw/eeprom93xx.c
@@ -114,7 +114,7 @@ static const VMStateInfo vmstate_hack_uint16_from_uint8 = {

  #define VMSTATE_UINT16_HACK_TEST(_f, _s, _t)                           \
-    VMSTATE_SINGLE_TEST(_f, _s, _t, 0, vmstate_hack_uint16_from_uint8, 
+    VMSTATE_SINGLE_TEST_HACK(_f, _s, _t, 0, vmstate_hack_uint16_from_uint8, 

  static bool is_old_eeprom_version(void *opaque, int version_id)
After the fact, we need to promote it as "full types".

Basically it is needed when we sent a field with a different size that
we use it on the struct.

if we have

struct FOOState {
        int32_t bar;

and it is sent as

VMSTATE_INT8(bar, ....)

In this case, I went through the whole device, checed that int8_t was
enough and did the change.

But if we have:

struct FOOState {
        int8_t bar;

and it is sent as

VMSTATE_INT32(bar, ....)

Then it is not trivial :-(

We change FOOState to int32 or we break migration format.  Here is where
the _HACK suffix appeared.

I thought it was not going to be needed a lot, but there are several
devices that just sent everything over the wire as uint32, independently
of its type.

Could we get away with just doing:

VMSTATE_UINT8(bar, ...),

That's fully compatible on the wire and seems to be a clearer expression of exactly what the problem is.


Anthony Liguori

Later, Juan.

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