Re: [Scst-devel] [PATCH] Fix iSCSI endianness warnings reported by sparse

[Bart V. A. <bva...@ac...>]

On Thu, Jul 15, 2010 at 9:16 PM, Vladislav Bolkhovitin <vs...@vl...> wrote:
>
> Bart Van Assche, on 07/11/2010 01:39 PM wrote:
> [ ... ]
>>>> --- iscsi-scst/kernel/digest.c  (revision 1792)
>>>> +++ iscsi-scst/kernel/digest.c  (working copy)
>>>> @@ -57,7 +57,7 @@ int digest_init(struct iscsi_conn *conn)
>>>>        return 0;
>>>>  }
>>>>
>>>> -static u32 evaluate_crc32_from_sg(struct scatterlist *sg, int nbytes,
>>>> +static __le32 evaluate_crc32_from_sg(struct scatterlist *sg, int nbytes,
>>>>        uint32_t padding)
>>>
>>> For what is enforcing it to LE32? Crc32c() returns u32, so what are the
>>> benefits of the additional conversion?
>>
>> The line "return ~cpu_to_le32(crc);" in evaluate_crc32_from_sg() makes its
>> return value __le32. A possible alternative for all the changes in
>> iscsi-scst/kernel/digest.c is to change that line into "return
>> (__force u32)~cpu_to_le32(crc);".
>
> Hmm, I don't like it. Both hdigest and ddigest are in the network form (BE),
> so, I think, we should use it as the starting point, not to pretend they both LE

Sparse still reports two endianness warnings on r1828. These can be
suppressed e.g.
as follows:

Index: iscsi-scst/kernel/iscsi.c
===================================================================
--- iscsi-scst/kernel/iscsi.c	(revision 1828)
+++ iscsi-scst/kernel/iscsi.c	(working copy)
@@ -1664,7 +1664,7 @@ static int nop_out_start(struct iscsi_cm
 		goto out;
 	}

-	if (cmnd->pdu.bhs.itt == ISCSI_RESERVED_TAG_CPU32) {
+	if (cmnd->pdu.bhs.itt == ISCSI_RESERVED_TAG) {
 		if (unlikely(!(cmnd->pdu.bhs.opcode & ISCSI_OP_IMMEDIATE)))
 			PRINT_ERROR("%s", "Initiator sent RESERVED tag for "
 				"non-immediate Nop-Out command");
Index: iscsi-scst/kernel/digest.c
===================================================================
--- iscsi-scst/kernel/digest.c	(revision 1828)
+++ iscsi-scst/kernel/digest.c	(working copy)
@@ -82,7 +82,7 @@ static u32 evaluate_crc32_from_sg(struct
 		crc = crc32c(crc, (u8 *)&padding, pad_bytes);
 #endif

-	return ~cpu_to_le32(crc);
+	return (__force __u32)~cpu_to_le32(crc);
 }

 static u32 digest_header(struct iscsi_pdu *pdu)