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Subject[PATCH 2/9] cciss: detect bad alignment of scsi commands at build time
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Date
From: Stephen M. Cameron <scameron@beardog.cce.hp.com>

cciss: detect bad alignment of scsi commands at build time
Incidentally fix some nearby c++ style comments.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
---
drivers/block/cciss.c | 2 +-
drivers/block/cciss_cmd.h | 9 ++++++---
drivers/block/cciss_scsi.c | 12 ++++++++----
3 files changed, 15 insertions(+), 8 deletions(-)
diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index a29e694..cd8c7c2 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -4496,7 +4496,7 @@ static int __init cciss_init(void)
* boundary. Given that we use pci_alloc_consistent() to allocate an
* array of them, the size must be a multiple of 8 bytes.
*/
- BUILD_BUG_ON(sizeof(CommandList_struct) % 8);
+ BUILD_BUG_ON(sizeof(CommandList_struct) % COMMANDLIST_ALIGNMENT);

printk(KERN_INFO DRIVER_NAME "\n");

diff --git a/drivers/block/cciss_cmd.h b/drivers/block/cciss_cmd.h
index 515c9f0..e624ff9 100644
--- a/drivers/block/cciss_cmd.h
+++ b/drivers/block/cciss_cmd.h
@@ -167,10 +167,13 @@ typedef struct _SGDescriptor_struct {
#define CMD_MSG_TIMEOUT 0x05
#define CMD_MSG_STALE 0xff

-/* This structure needs to be divisible by 8 for new
- * indexing method. PAD_32 and PAD_64 can be adjusted
- * independently as needed for 32-bit and 64-bits systems.
+/* This structure needs to be divisible by COMMANDLIST_ALIGNMENT
+ * because low bits of the address are used to to indicate that
+ * whether the tag contains an index or an address. PAD_32 and
+ * PAD_64 can be adjusted independently as needed for 32-bit
+ * and 64-bits systems.
*/
+#define COMMANDLIST_ALIGNMENT (8)
#define IS_64_BIT ((sizeof(long) - 4)/4)
#define IS_32_BIT (!IS_64_BIT)
#define PAD_32 (0)
diff --git a/drivers/block/cciss_scsi.c b/drivers/block/cciss_scsi.c
index 5d0e46d..f203606 100644
--- a/drivers/block/cciss_scsi.c
+++ b/drivers/block/cciss_scsi.c
@@ -93,11 +93,15 @@ static struct scsi_host_template cciss_driver_template = {
};

#pragma pack(1)
+
+#define SCSI_PAD_32 4
+#define SCSI_PAD_64 4
+
struct cciss_scsi_cmd_stack_elem_t {
CommandList_struct cmd;
ErrorInfo_struct Err;
__u32 busaddr;
- __u32 pad;
+ u8 pad[IS_32_BIT * SCSI_PAD_32 + IS_64_BIT * SCSI_PAD_64];
};

#pragma pack()
@@ -202,9 +206,9 @@ scsi_cmd_stack_setup(int ctlr, struct cciss_scsi_adapter_data_t *sa)
stk = &sa->cmd_stack;
size = sizeof(struct cciss_scsi_cmd_stack_elem_t) * CMD_STACK_SIZE;

- // pci_alloc_consistent guarantees 32-bit DMA address will
- // be used
-
+ /* Check alignment, see cciss_cmd.h near CommandList_struct def. */
+ BUILD_BUG_ON((sizeof(*stk->pool) % COMMANDLIST_ALIGNMENT) != 0);
+ /* pci_alloc_consistent guarantees 32-bit DMA address will be used */
stk->pool = (struct cciss_scsi_cmd_stack_elem_t *)
pci_alloc_consistent(hba[ctlr]->pdev, size, &stk->cmd_pool_handle);



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