RE: [PATCH 3/6] powerpc/powernv: Replace variables with flags

2013-06-26 Thread David Laight 
 We have 2 fields in struct pnv_phb to trace the states. The patch
 replace the fields with one and introduces flags for that. The patch
 doesn't impact the logic.

What is the benefit of this change?

...
 +
 +#define PNV_EEH_STATE_ENABLED(1  0)/* EEH enabled  */
 +#define PNV_EEH_STATE_REMOVED(1  1)/* PHB removed  */
 +
  #endif /* CONFIG_EEH */
 
  struct pnv_phb {
 @@ -92,8 +96,7 @@ struct pnv_phb {
 
  #ifdef CONFIG_EEH
   struct pnv_eeh_ops  *eeh_ops;
 - int eeh_enabled;
 - int removed;
 + int eeh_state;
  #endif
 
  #ifdef CONFIG_DEBUG_FS

All I can see is that it possibly reduces a structure by 4 bytes
while adding extra code.
(On 64 bit systems there might be a 4 byte pad added.)

David



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Re: [PATCH 3/6] powerpc/powernv: Replace variables with flags

2013-06-26 Thread Gavin Shan 
On Wed, Jun 26, 2013 at 10:12:16AM +0100, David Laight wrote:
 We have 2 fields in struct pnv_phb to trace the states. The patch
 replace the fields with one and introduces flags for that. The patch
 doesn't impact the logic.

What is the benefit of this change?


There might have more flags coming in. Putting all flags together
could be maintained more easily. It doesn't save much memory as
you pointed.

 +
 +#define PNV_EEH_STATE_ENABLED   (1  0)/* EEH enabled  */
 +#define PNV_EEH_STATE_REMOVED   (1  1)/* PHB removed  */
 +
  #endif /* CONFIG_EEH */
 
  struct pnv_phb {
 @@ -92,8 +96,7 @@ struct pnv_phb {
 
  #ifdef CONFIG_EEH
  struct pnv_eeh_ops  *eeh_ops;
 -int eeh_enabled;
 -int removed;
 +int eeh_state;
  #endif
 
  #ifdef CONFIG_DEBUG_FS

All I can see is that it possibly reduces a structure by 4 bytes
while adding extra code.
(On 64 bit systems there might be a 4 byte pad added.)


Thanks,
Gavin

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