linux-kernel - [PATCH 3/3] infiniband: hns: avoid gcc-7.0.1 warning for uninitialized data

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Message-Id: <20170323145610.54695-3-arnd@arndb.de>
Date:   Thu, 23 Mar 2017 15:55:52 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Lijun Ou <oulijun@...wei.com>,
        "Wei Hu(Xavier)" <xavier.huwei@...wei.com>,
        Doug Ledford <dledford@...hat.com>,
        Sean Hefty <sean.hefty@...el.com>,
        Hal Rosenstock <hal.rosenstock@...il.com>
Cc:     Arnd Bergmann <arnd@...db.de>, Salil <salil.mehta@...wei.com>,
        "Dongdong Huang(Donald)" <hdd.huang@...wei.com>,
        Shaobo Xu <xushaobo2@...wei.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] infiniband: hns: avoid gcc-7.0.1 warning for uninitialized data

hns_roce_v1_cq_set_ci() calls roce_set_bit() on an uninitialized field,
which will then change only a few of its bits, causing a warning with
the latest gcc:

infiniband/hw/hns/hns_roce_hw_v1.c: In function 'hns_roce_v1_cq_set_ci':
infiniband/hw/hns/hns_roce_hw_v1.c:1854:23: error: 'doorbell[1]' is used uninitialized in this function [-Werror=uninitialized]
  roce_set_bit(doorbell[1], ROCEE_DB_OTHERS_H_ROCEE_DB_OTH_HW_SYNS_S, 1);

The code is actually correct since we always set all bits of the
port_vlan field, but gcc correctly points out that the first
access does contain uninitialized data.

This initializes the field to zero first before setting the
individual bits.

Fixes: 9a4435375cd1 ("IB/hns: Add driver files for hns RoCE driver")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/infiniband/hw/hns/hns_roce_hw_v1.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/infiniband/hw/hns/hns_roce_hw_v1.c b/drivers/infiniband/hw/hns/hns_roce_hw_v1.c
index ec68f56e8ee5..882073a6ec77 100644
--- a/drivers/infiniband/hw/hns/hns_roce_hw_v1.c
+++ b/drivers/infiniband/hw/hns/hns_roce_hw_v1.c
@@ -1851,6 +1851,7 @@ void hns_roce_v1_cq_set_ci(struct hns_roce_cq *hr_cq, u32 cons_index)
 	u32 doorbell[2];
 
 	doorbell[0] = cons_index & ((hr_cq->cq_depth << 1) - 1);
+	doorbell[1] = 0;
 	roce_set_bit(doorbell[1], ROCEE_DB_OTHERS_H_ROCEE_DB_OTH_HW_SYNS_S, 1);
 	roce_set_field(doorbell[1], ROCEE_DB_OTHERS_H_ROCEE_DB_OTH_CMD_M,
 		       ROCEE_DB_OTHERS_H_ROCEE_DB_OTH_CMD_S, 3);
-- 
2.9.0