Re: [PATCH] drm/amd/display: Fix an uninitialized index variable
From: Nick Desaulniers
Date: Thu Feb 25 2021 - 16:34:55 EST
On Thu, Feb 25, 2021 at 7:01 AM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
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From: Arnd Bergmann <arnd@xxxxxxxx>
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clang points out that the new logic uses an always-uninitialized
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array index:
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drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:9810:38: warning: variable 'i' is uninitialized when used here [-Wuninitialized]
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timing = &edid->detailed_timings[i];
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^
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drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:9720:7: note: initialize the variable 'i' to silence this warning
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My best guess is that the index should have been returned by the
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parse_hdmi_amd_vsdb() function that walks an array here, so do that.
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Fixes: f9b4f20c4777 ("drm/amd/display: Add Freesync HDMI support to DM")
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Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
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---
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.../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 16 ++++++++--------
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1 file changed, 8 insertions(+), 8 deletions(-)
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diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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index b19b93c74bae..667c0d52dbfa 100644
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--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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@@ -9736,7 +9736,7 @@ static bool parse_edid_cea(struct amdgpu_dm_connector *aconnector,
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return false;
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}
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-static bool parse_hdmi_amd_vsdb(struct amdgpu_dm_connector *aconnector,
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+static int parse_hdmi_amd_vsdb(struct amdgpu_dm_connector *aconnector,
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struct edid *edid, struct amdgpu_hdmi_vsdb_info *vsdb_info)
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{
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uint8_t *edid_ext = NULL;
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@@ -9746,7 +9746,7 @@ static bool parse_hdmi_amd_vsdb(struct amdgpu_dm_connector *aconnector,
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/*----- drm_find_cea_extension() -----*/
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/* No EDID or EDID extensions */
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if (edid == NULL || edid->extensions == 0)
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- return false;
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+ return -ENODEV;
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/* Find CEA extension */
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for (i = 0; i < edid->extensions; i++) {
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@@ -9756,14 +9756,15 @@ static bool parse_hdmi_amd_vsdb(struct amdgpu_dm_connector *aconnector,
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}
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if (i == edid->extensions)
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- return false;
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+ return -ENODEV;
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/*----- cea_db_offsets() -----*/
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if (edid_ext[0] != CEA_EXT)
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- return false;
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+ return -ENODEV;
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valid_vsdb_found = parse_edid_cea(aconnector, edid_ext, EDID_LENGTH, vsdb_info);
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- return valid_vsdb_found;
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+
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+ return valid_vsdb_found ? i : -ENODEV;
Thanks for the patch!
I don't think we need a local variable to store the return value from
one function call that's immediately returned, ie.
return parse_edid_cea(aconnector, edid_ext, EDID_LENGTH, vsdb_info) ?
i : -ENODEV;
would suffice, but the patch is still fine as is.
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
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}
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void amdgpu_dm_update_freesync_caps(struct drm_connector *connector,
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@@ -9781,7 +9782,6 @@ void amdgpu_dm_update_freesync_caps(struct drm_connector *connector,
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struct amdgpu_device *adev = drm_to_adev(dev);
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bool freesync_capable = false;
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struct amdgpu_hdmi_vsdb_info vsdb_info = {0};
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- bool hdmi_valid_vsdb_found = false;
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if (!connector->state) {
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DRM_ERROR("%s - Connector has no state", __func__);
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@@ -9857,8 +9857,8 @@ void amdgpu_dm_update_freesync_caps(struct drm_connector *connector,
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}
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}
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} else if (edid && amdgpu_dm_connector->dc_sink->sink_signal == SIGNAL_TYPE_HDMI_TYPE_A) {
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- hdmi_valid_vsdb_found = parse_hdmi_amd_vsdb(amdgpu_dm_connector, edid, &vsdb_info);
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- if (hdmi_valid_vsdb_found && vsdb_info.freesync_supported) {
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+ i = parse_hdmi_amd_vsdb(amdgpu_dm_connector, edid, &vsdb_info);
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+ if (i >= 0 && vsdb_info.freesync_supported) {
reusing `i` here is safe, for now, but reuse of variables like this in
separate branches like this might not get noticed if the function is
amended in the future.
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timing = &edid->detailed_timings[i];
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data = &timing->data.other_data;
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--
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2.29.2
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--
Thanks,
~Nick Desaulniers