linux-kernel - [PATCH 4.9 164/172] infiniband: hns: avoid gcc-7.0.1 warning for uninitialized data

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Date:   Mon,  3 Jul 2017 15:35:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Doug Ledford <dledford@...hat.com>
Subject: [PATCH 4.9 164/172] infiniband: hns: avoid gcc-7.0.1 warning for uninitialized data

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@...db.de>

commit 5b0ff9a00755d4d9c209033a77f1ed8f3186fe5c upstream.

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>
Signed-off-by: Doug Ledford <dledford@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/infiniband/hw/hns/hns_roce_hw_v1.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/infiniband/hw/hns/hns_roce_hw_v1.c
+++ b/drivers/infiniband/hw/hns/hns_roce_hw_v1.c
@@ -1267,6 +1267,7 @@ void hns_roce_v1_cq_set_ci(struct hns_ro
 	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);