From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754010AbcIDS6U (ORCPT ); Sun, 4 Sep 2016 14:58:20 -0400 Received: from mx1.polytechnique.org ([129.104.30.34]:45094 "EHLO mx1.polytechnique.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751539AbcIDS6S (ORCPT ); Sun, 4 Sep 2016 14:58:18 -0400 From: Nicolas Iooss To: Daniel Vetter , Jani Nikula , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org, Nicolas Iooss Subject: [PATCH 1/1] drm/i915/dsi: silence a warning about uninitialized return value Date: Sun, 4 Sep 2016 20:58:09 +0200 Message-Id: <20160904185809.31916-1-nicolas.iooss_linux@m4x.org> X-Mailer: git-send-email 2.9.3 X-AV-Checked: ClamAV using ClamSMTP at svoboda.polytechnique.org (Sun Sep 4 20:58:14 2016 +0200 (CEST)) X-Spam-Flag: No, tests=bogofilter, spamicity=0.000309, queueID=C69A3564723 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When building the kernel with clang and some warning flags, the compiler reports that the return value of dcs_get_backlight() may be uninitialized: drivers/gpu/drm/i915/intel_dsi_dcs_backlight.c:53:2: error: variable 'data' is used uninitialized whenever 'for' loop exits because its condition is false [-Werror,-Wsometimes-uninitialized] for_each_dsi_port(port, intel_dsi->dcs_backlight_ports) { ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/i915/intel_dsi.h:126:49: note: expanded from macro 'for_each_dsi_port' #define for_each_dsi_port(__port, __ports_mask) for_each_port_masked(__port, __ports_mask) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/i915/i915_drv.h:322:26: note: expanded from macro 'for_each_port_masked' for ((__port) = PORT_A; (__port) < I915_MAX_PORTS; (__port)++) \ ^~~~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/i915/intel_dsi_dcs_backlight.c:60:9: note: uninitialized use occurs here return data; ^~~~ As intel_dsi->dcs_backlight_ports seems to be always initialized to a non-null value, the content of the for loop is always executed and there is no bug in the current code. Nevertheless the compiler has no way of knowing that assumption, so initialize variable 'data' to silence the warning here. Signed-off-by: Nicolas Iooss --- drivers/gpu/drm/i915/intel_dsi_dcs_backlight.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_dsi_dcs_backlight.c b/drivers/gpu/drm/i915/intel_dsi_dcs_backlight.c index ac7c6020c443..eec45856f910 100644 --- a/drivers/gpu/drm/i915/intel_dsi_dcs_backlight.c +++ b/drivers/gpu/drm/i915/intel_dsi_dcs_backlight.c @@ -46,7 +46,7 @@ static u32 dcs_get_backlight(struct intel_connector *connector) struct intel_encoder *encoder = connector->encoder; struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base); struct mipi_dsi_device *dsi_device; - u8 data; + u8 data = 0; enum port port; /* FIXME: Need to take care of 16 bit brightness level */ -- 2.9.3