am65-cpsw: avoid null pointer arithmetic

clang warns about arithmetic on NULL pointers:

drivers/net/ethernet/ti/am65-cpsw-ethtool.c:71:2: error: performing pointer subtraction with a null pointer has undefined behavior [-Werror,-Wnull-pointer-subtraction]
        AM65_CPSW_REGDUMP_REC(AM65_CPSW_REGDUMP_MOD_NUSS, 0x0, 0x1c),
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/ti/am65-cpsw-ethtool.c:64:29: note: expanded from macro 'AM65_CPSW_REGDUMP_REC'
        .hdr.len = (((u32 *)(end)) - ((u32 *)(start)) + 1) * sizeof(u32) * 2 + \
                                   ^ ~~~~~~~~~~~~~~~~

The expression here is easily changed to a calculation based on integers
that is no less readable.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/ti/am65-cpsw-ethtool.c b/drivers/net/ethernet/ti/am65-cpsw-ethtool.c
index 6e4d4f9..b05de9b 100644 (file)
--- a/drivers/net/ethernet/ti/am65-cpsw-ethtool.c
+++ b/drivers/net/ethernet/ti/am65-cpsw-ethtool.c
@@ -61,7 +61,7 @@ struct am65_cpsw_regdump_item {
 
 #define AM65_CPSW_REGDUMP_REC(mod, start, end) { \
        .hdr.module_id = (mod), \
-       .hdr.len = (((u32 *)(end)) - ((u32 *)(start)) + 1) * sizeof(u32) * 2 + \
+       .hdr.len = (end + 4 - start) * 2 + \
                   sizeof(struct am65_cpsw_regdump_hdr), \
        .start_ofs = (start), \
        .end_ofs = end, \