From: Matt Roper <matthew.d.roper@intel.com>
To: Nathan Chancellor <natechancellor@gmail.com>
Cc: intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org,
clang-built-linux@googlegroups.com,
"José Roberto de Souza" <jose.souza@intel.com>,
"Rodrigo Vivi" <rodrigo.vivi@intel.com>
Subject: Re: [PATCH] drm/i915/display: Ensure that ret is always initialized in icl_combo_phy_verify_state
Date: Wed, 15 Jul 2020 22:31:24 -0700 [thread overview]
Message-ID: <20200716053124.GE2588642@mdroper-desk1.amr.corp.intel.com> (raw)
In-Reply-To: <20200716042742.123169-1-natechancellor@gmail.com>
On Wed, Jul 15, 2020 at 09:27:42PM -0700, Nathan Chancellor wrote:
> Clang warns:
>
> drivers/gpu/drm/i915/display/intel_combo_phy.c:268:3: warning: variable
> 'ret' is uninitialized when used here [-Wuninitialized]
> ret &= check_phy_reg(dev_priv, phy, ICL_PORT_TX_DW8_LN0(phy),
> ^~~
> drivers/gpu/drm/i915/display/intel_combo_phy.c:261:10: note: initialize
> the variable 'ret' to silence this warning
> bool ret;
> ^
> = 0
> 1 warning generated.
>
> In practice, the bug this warning appears to be concerned with would not
> actually matter because ret gets initialized to the return value of
> cnl_verify_procmon_ref_values. However, that does appear to be a bug
> since it means the first hunk of the patch this fixes won't actually do
> anything (since the values of check_phy_reg won't factor into the final
> ret value). Initialize ret to true then make all of the assignments a
> bitwise AND with itself so that the function always does what it should
> do.
>
> Fixes: 239bef676d8e ("drm/i915/display: Implement new combo phy initialization step")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1094
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
> ---
> drivers/gpu/drm/i915/display/intel_combo_phy.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_combo_phy.c b/drivers/gpu/drm/i915/display/intel_combo_phy.c
> index eccaa79cb4a9..a4b8aa6d0a9e 100644
> --- a/drivers/gpu/drm/i915/display/intel_combo_phy.c
> +++ b/drivers/gpu/drm/i915/display/intel_combo_phy.c
> @@ -258,7 +258,7 @@ static bool phy_is_master(struct drm_i915_private *dev_priv, enum phy phy)
> static bool icl_combo_phy_verify_state(struct drm_i915_private *dev_priv,
> enum phy phy)
> {
> - bool ret;
> + bool ret = true;
> u32 expected_val = 0;
>
> if (!icl_combo_phy_enabled(dev_priv, phy))
> @@ -276,7 +276,7 @@ static bool icl_combo_phy_verify_state(struct drm_i915_private *dev_priv,
> DCC_MODE_SELECT_CONTINUOSLY);
> }
>
> - ret = cnl_verify_procmon_ref_values(dev_priv, phy);
> + ret &= cnl_verify_procmon_ref_values(dev_priv, phy);
>
> if (phy_is_master(dev_priv, phy)) {
> ret &= check_phy_reg(dev_priv, phy, ICL_PORT_COMP_DW8(phy),
>
> base-commit: ca0e494af5edb59002665bf12871e94b4163a257
> --
> 2.28.0.rc0
>
--
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation
(916) 356-2795
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prev parent reply other threads:[~2020-07-16 5:31 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-16 4:27 [PATCH] drm/i915/display: Ensure that ret is always initialized in icl_combo_phy_verify_state Nathan Chancellor
2020-07-16 5:31 ` Matt Roper [this message]
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