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[SCSI] hpsa: Clarify calculation of padding for commandlist structure

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Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
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Stephen M. Cameron 2010-02-25 14:03:22 -06:00 committed by James Bottomley
parent ff9fea9454
commit db61bfcfe2
1 changed files with 10 additions and 4 deletions
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14
drivers/scsi/hpsa_cmd.h
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@ -313,12 +313,18 @@ struct CommandList {
void *scsi_cmd;
/* on 64 bit architectures, to get this to be 32-byte-aligned
* it so happens we need no padding, on 32 bit systems,
* we need 8 bytes of padding. This does that.
* it so happens we need PAD_64 bytes of padding, on 32 bit systems,
* we need PAD_32 bytes of padding (see below). This does that.
* If it happens that 64 bit and 32 bit systems need different
* padding, PAD_32 and PAD_64 can be set independently, and.
* the code below will do the right thing.
*/
#define COMMANDLIST_PAD ((8 - sizeof(long))/4 * 8)
#define IS_32_BIT ((8 - sizeof(long))/4)
#define IS_64_BIT (!IS_32_BIT)
#define PAD_32 (8)
#define PAD_64 (0)
#define COMMANDLIST_PAD (IS_32_BIT * PAD_32 + IS_64_BIT * PAD_64)
u8 pad[COMMANDLIST_PAD];
};
/* Configuration Table Structure */