drm/i915/dsi: be defensive about out of bounds operation byte

Untie the VBT based generic panel driver from the VBT parsing, so that
the two don't have to be updated in lockstep.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/01c71ac89a9db8bc7b8ae0fb05c50a5fae362dc4.1450702954.git.jani.nikula@intel.com

diff --git a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
index c6aea69..9bd9208 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
+++ b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
@@ -232,11 +232,9 @@ static const u8 *mipi_exec_gpio(struct intel_dsi *intel_dsi, const u8 *data)
 typedef const u8 * (*fn_mipi_elem_exec)(struct intel_dsi *intel_dsi,
                                        const u8 *data);
 static const fn_mipi_elem_exec exec_elem[] = {
-       NULL, /* reserved */
-       mipi_exec_send_packet,
-       mipi_exec_delay,
-       mipi_exec_gpio,
-       NULL, /* status read; later */
+       [MIPI_SEQ_ELEM_SEND_PKT] = mipi_exec_send_packet,
+       [MIPI_SEQ_ELEM_DELAY] = mipi_exec_delay,
+       [MIPI_SEQ_ELEM_GPIO] = mipi_exec_gpio,
 };
 
 /*
@@ -264,7 +262,6 @@ static const char *sequence_name(enum mipi_seq seq_id)
 static void generic_exec_sequence(struct intel_dsi *intel_dsi, const u8 *data)
 {
        fn_mipi_elem_exec mipi_elem_exec;
-       int index;
 
        if (!data)
                return;
@@ -277,15 +274,14 @@ static void generic_exec_sequence(struct intel_dsi *intel_dsi, const u8 *data)
 
        /* parse each byte till we reach end of sequence byte - 0x00 */
        while (1) {
-               index = *data;
-               mipi_elem_exec = exec_elem[index];
-               if (!mipi_elem_exec) {
-                       DRM_ERROR("Unsupported MIPI element, skipping sequence execution\n");
+               u8 operation_byte = *data++;
+               if (operation_byte >= ARRAY_SIZE(exec_elem) ||
+                   !exec_elem[operation_byte]) {
+                       DRM_ERROR("Unsupported MIPI operation byte %u\n",
+                                 operation_byte);
                        return;
                }
-
-               /* goto element payload */
-               data++;
+               mipi_elem_exec = exec_elem[operation_byte];
 
                /* execute the element specific rotines */
                data = mipi_elem_exec(intel_dsi, data);