crypto: hisilicon/sgl - add a comment for block size initialization

This seems "32" and "31" is obfuscating, It might be better to add a comment,
which explain it.

Signed-off-by: Kai Ye <yekai13@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/crypto/hisilicon/sgl.c b/drivers/crypto/hisilicon/sgl.c
index 3bff639..cf1629c 100644 (file)
--- a/drivers/crypto/hisilicon/sgl.c
+++ b/drivers/crypto/hisilicon/sgl.c
@@ -66,6 +66,11 @@ struct hisi_acc_sgl_pool *hisi_acc_create_sgl_pool(struct device *dev,
 
        sgl_size = sizeof(struct acc_hw_sge) * sge_nr +
                   sizeof(struct hisi_acc_hw_sgl);
+
+       /*
+        * the pool may allocate a block of memory of size PAGE_SIZE * 2^(MAX_ORDER - 1),
+        * block size may exceed 2^31 on ia64, so the max of block size is 2^31
+        */
        block_size = 1 << (PAGE_SHIFT + MAX_ORDER <= 32 ?
                           PAGE_SHIFT + MAX_ORDER - 1 : 31);
        sgl_num_per_block = block_size / sgl_size;