drm/imx: imx-ldb: fix out of bounds array access warning

When CONFIG_OF is disabled, building with 'make W=1' produces warnings
about out of bounds array access:

drivers/gpu/drm/imx/imx-ldb.c: In function 'imx_ldb_set_clock.constprop':
drivers/gpu/drm/imx/imx-ldb.c:186:8: error: array subscript -22 is below array bounds of 'struct clk *[4]' [-Werror=array-bounds]

Add an error check before the index is used, which helps with the
warning, as well as any possible other error condition that may be
triggered at runtime.

The warning could be fixed by adding a Kconfig depedency on CONFIG_OF,
but Liu Ying points out that the driver may hit the out-of-bounds
problem at runtime anyway.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Liu Ying <victor.liu@nxp.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
index b794ed448ea394ebdb29e71e62c8f165b0b29c96..ffdc492c5bc51ea2d5727bd701ef18e3c34df4f0 100644 (file)
--- a/drivers/gpu/drm/imx/imx-ldb.c
+++ b/drivers/gpu/drm/imx/imx-ldb.c
@@ -197,6 +197,11 @@ static void imx_ldb_encoder_enable(struct drm_encoder *encoder)
        int dual = ldb->ldb_ctrl & LDB_SPLIT_MODE_EN;
        int mux = drm_of_encoder_active_port_id(imx_ldb_ch->child, encoder);
 
+       if (mux < 0 || mux >= ARRAY_SIZE(ldb->clk_sel)) {
+               dev_warn(ldb->dev, "%s: invalid mux %d\n", __func__, mux);
+               return;
+       }
+
        drm_panel_prepare(imx_ldb_ch->panel);
 
        if (dual) {
@@ -255,6 +260,11 @@ imx_ldb_encoder_atomic_mode_set(struct drm_encoder *encoder,
        int mux = drm_of_encoder_active_port_id(imx_ldb_ch->child, encoder);
        u32 bus_format = imx_ldb_ch->bus_format;
 
+       if (mux < 0 || mux >= ARRAY_SIZE(ldb->clk_sel)) {
+               dev_warn(ldb->dev, "%s: invalid mux %d\n", __func__, mux);
+               return;
+       }
+
        if (mode->clock > 170000) {
                dev_warn(ldb->dev,
                         "%s: mode exceeds 170 MHz pixel clock\n", __func__);