drm/i915: constify validate_vbt in VBT parsing

Make input and output of validate_vbt const, and fix the fallout. We
shouldn't modify the VBT, so make the compiler help us here.

v2: use pointer arithmetics on void* to simplify (Ville)

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 5876e7c..cbd16c0 100644 (file)
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -205,7 +205,7 @@ get_lvds_fp_timing(const struct bdb_header *bdb,
 /* Try to find integrated panel data */
 static void
 parse_lfp_panel_data(struct drm_i915_private *dev_priv,
-                           struct bdb_header *bdb)
+                    const struct bdb_header *bdb)
 {
        const struct bdb_lvds_options *lvds_options;
        const struct bdb_lvds_lfp_data *lvds_lfp_data;
@@ -311,7 +311,8 @@ parse_lfp_panel_data(struct drm_i915_private *dev_priv,
 }
 
 static void
-parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
+parse_lfp_backlight(struct drm_i915_private *dev_priv,
+                   const struct bdb_header *bdb)
 {
        const struct bdb_lfp_backlight_data *backlight_data;
        const struct bdb_lfp_backlight_data_entry *entry;
@@ -349,7 +350,7 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
 /* Try to find sdvo panel data */
 static void
 parse_sdvo_panel_data(struct drm_i915_private *dev_priv,
-                     struct bdb_header *bdb)
+                     const struct bdb_header *bdb)
 {
        const struct lvds_dvo_timing *dvo_timing;
        struct drm_display_mode *panel_fixed_mode;
@@ -403,7 +404,7 @@ static int intel_bios_ssc_frequency(struct drm_device *dev,
 
 static void
 parse_general_features(struct drm_i915_private *dev_priv,
-                      struct bdb_header *bdb)
+                      const struct bdb_header *bdb)
 {
        struct drm_device *dev = dev_priv->dev;
        const struct bdb_general_features *general;
@@ -429,7 +430,7 @@ parse_general_features(struct drm_i915_private *dev_priv,
 
 static void
 parse_general_definitions(struct drm_i915_private *dev_priv,
-                         struct bdb_header *bdb)
+                         const struct bdb_header *bdb)
 {
        const struct bdb_general_definitions *general;
 
@@ -456,7 +457,7 @@ child_device_ptr(const struct bdb_general_definitions *p_defs, int i)
 
 static void
 parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
-                         struct bdb_header *bdb)
+                         const struct bdb_header *bdb)
 {
        struct sdvo_device_mapping *p_mapping;
        const struct bdb_general_definitions *p_defs;
@@ -546,7 +547,7 @@ parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
 
 static void
 parse_driver_features(struct drm_i915_private *dev_priv,
-                      struct bdb_header *bdb)
+                     const struct bdb_header *bdb)
 {
        const struct bdb_driver_features *driver;
 
@@ -572,7 +573,7 @@ parse_driver_features(struct drm_i915_private *dev_priv,
 }
 
 static void
-parse_edp(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
+parse_edp(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
 {
        const struct bdb_edp *edp;
        const struct edp_power_seq *edp_pps;
@@ -684,7 +685,7 @@ parse_edp(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
 }
 
 static void
-parse_psr(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
+parse_psr(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
 {
        const struct bdb_psr *psr;
        const struct psr_table *psr_table;
@@ -795,7 +796,7 @@ static u8 *goto_next_sequence(u8 *data, int *size)
 }
 
 static void
-parse_mipi(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
+parse_mipi(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
 {
        const struct bdb_mipi_config *start;
        const struct bdb_mipi_sequence *sequence;
@@ -946,7 +947,7 @@ err:
 }
 
 static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
-                          struct bdb_header *bdb)
+                          const struct bdb_header *bdb)
 {
        union child_device_config *it, *child = NULL;
        struct ddi_vbt_port_info *info = &dev_priv->vbt.ddi_port_info[port];
@@ -1048,7 +1049,7 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
 }
 
 static void parse_ddi_ports(struct drm_i915_private *dev_priv,
-                           struct bdb_header *bdb)
+                           const struct bdb_header *bdb)
 {
        struct drm_device *dev = dev_priv->dev;
        enum port port;
@@ -1068,7 +1069,7 @@ static void parse_ddi_ports(struct drm_i915_private *dev_priv,
 
 static void
 parse_device_mapping(struct drm_i915_private *dev_priv,
-                      struct bdb_header *bdb)
+                    const struct bdb_header *bdb)
 {
        const struct bdb_general_definitions *p_defs;
        const union child_device_config *p_child;
@@ -1198,19 +1199,20 @@ static const struct dmi_system_id intel_no_opregion_vbt[] = {
        { }
 };
 
-static struct bdb_header *validate_vbt(char *base, size_t size,
-                                      struct vbt_header *vbt,
-                                      const char *source)
+static const struct bdb_header *validate_vbt(const void *base, size_t size,
+                                            const void *_vbt,
+                                            const char *source)
 {
+       const struct vbt_header *vbt = _vbt;
        size_t offset;
-       struct bdb_header *bdb;
+       const struct bdb_header *bdb;
 
        if (vbt == NULL) {
                DRM_DEBUG_DRIVER("VBT signature missing\n");
                return NULL;
        }
 
-       offset = (char *)vbt - base;
+       offset = _vbt - base;
        if (offset + sizeof(struct vbt_header) > size) {
                DRM_DEBUG_DRIVER("VBT header incomplete\n");
                return NULL;
@@ -1227,7 +1229,7 @@ static struct bdb_header *validate_vbt(char *base, size_t size,
                return NULL;
        }
 
-       bdb = (struct bdb_header *)(base + offset);
+       bdb = base + offset;
        if (offset + bdb->bdb_size > size) {
                DRM_DEBUG_DRIVER("BDB incomplete\n");
                return NULL;
@@ -1252,7 +1254,7 @@ intel_parse_bios(struct drm_device *dev)
 {
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct pci_dev *pdev = dev->pdev;
-       struct bdb_header *bdb = NULL;
+       const struct bdb_header *bdb = NULL;
        u8 __iomem *bios = NULL;
 
        if (HAS_PCH_NOP(dev))
@@ -1262,9 +1264,8 @@ intel_parse_bios(struct drm_device *dev)
 
        /* XXX Should this validation be moved to intel_opregion.c? */
        if (!dmi_check_system(intel_no_opregion_vbt) && dev_priv->opregion.vbt)
-               bdb = validate_vbt((char *)dev_priv->opregion.header, OPREGION_SIZE,
-                                  (struct vbt_header *)dev_priv->opregion.vbt,
-                                  "OpRegion");
+               bdb = validate_vbt(dev_priv->opregion.header, OPREGION_SIZE,
+                                  dev_priv->opregion.vbt, "OpRegion");
 
        if (bdb == NULL) {
                size_t i, size;
@@ -1277,7 +1278,7 @@ intel_parse_bios(struct drm_device *dev)
                for (i = 0; i + 4 < size; i++) {
                        if (memcmp(bios + i, "$VBT", 4) == 0) {
                                bdb = validate_vbt(bios, size,
-                                                  (struct vbt_header *)(bios + i),
+                                                  bios + i,
                                                   "PCI ROM");
                                break;
                        }