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    Subject[PATCH 6.0 358/862] drm/dp_mst: fix drm_dp_dpcd_read return value checks
    Date
    From: Simon Ser <contact@emersion.fr>

    [ Upstream commit 2ac6cdd581f48c8f68747156fde5868486a44985 ]

    drm_dp_dpcd_read returns the number of bytes read. The previous code
    would print garbage on DPCD error, and would exit with on error on
    success.

    Signed-off-by: Simon Ser <contact@emersion.fr>
    Fixes: cb897542c6d2 ("drm/dp_mst: Fix W=1 warnings")
    Cc: Lyude Paul <lyude@redhat.com>
    Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
    Reviewed-by: Jani Nikula <jani.nikula@intel.com>
    Link: https://patchwork.freedesktop.org/patch/473500/
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/gpu/drm/display/drm_dp_mst_topology.c | 6 +++---
    1 file changed, 3 insertions(+), 3 deletions(-)

    diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
    index 57e65423e50d..7a94a5288e8d 100644
    --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
    +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
    @@ -4907,14 +4907,14 @@ void drm_dp_mst_dump_topology(struct seq_file *m,
    seq_printf(m, "dpcd: %*ph\n", DP_RECEIVER_CAP_SIZE, buf);

    ret = drm_dp_dpcd_read(mgr->aux, DP_FAUX_CAP, buf, 2);
    - if (ret) {
    + if (ret != 2) {
    seq_printf(m, "faux/mst read failed\n");
    goto out;
    }
    seq_printf(m, "faux/mst: %*ph\n", 2, buf);

    ret = drm_dp_dpcd_read(mgr->aux, DP_MSTM_CTRL, buf, 1);
    - if (ret) {
    + if (ret != 1) {
    seq_printf(m, "mst ctrl read failed\n");
    goto out;
    }
    @@ -4922,7 +4922,7 @@ void drm_dp_mst_dump_topology(struct seq_file *m,

    /* dump the standard OUI branch header */
    ret = drm_dp_dpcd_read(mgr->aux, DP_BRANCH_OUI, buf, DP_BRANCH_OUI_HEADER_SIZE);
    - if (ret) {
    + if (ret != DP_BRANCH_OUI_HEADER_SIZE) {
    seq_printf(m, "branch oui read failed\n");
    goto out;
    }
    --
    2.35.1


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