struct _drm_i915_sarea *sarea_priv;
 };
 #define I915_FENCE_REG_NONE -1
+#define I915_MAX_NUM_FENCES 16
+/* 16 fences + sign bit for FENCE_REG_NONE */
+#define I915_MAX_NUM_FENCE_BITS 5
 
 struct drm_i915_fence_reg {
        struct list_head lru_list;
        u32 instdone1;
        u32 seqno;
        u64 bbaddr;
-       u64 fence[16];
+       u64 fence[I915_MAX_NUM_FENCES];
        struct timeval time;
        struct drm_i915_error_object {
                int page_count;
                u32 gtt_offset;
                u32 read_domains;
                u32 write_domain;
-               s32 fence_reg:5;
+               s32 fence_reg:I915_MAX_NUM_FENCE_BITS;
                s32 pinned:2;
                u32 tiling:2;
                u32 dirty:1;
        struct notifier_block lid_notifier;
 
        int crt_ddc_pin;
-       struct drm_i915_fence_reg fence_regs[16]; /* assume 965 */
+       struct drm_i915_fence_reg fence_regs[I915_MAX_NUM_FENCES]; /* assume 965 */
        int fence_reg_start; /* 4 if userland hasn't ioctl'd us yet */
        int num_fence_regs; /* 8 on pre-965, 16 otherwise */
 
        u8 saveAR[21];
        u8 saveDACMASK;
        u8 saveCR[37];
-       uint64_t saveFENCE[16];
+       uint64_t saveFENCE[I915_MAX_NUM_FENCES];
        u32 saveCURACNTR;
        u32 saveCURAPOS;
        u32 saveCURABASE;
         * Fence register bits (if any) for this object.  Will be set
         * as needed when mapped into the GTT.
         * Protected by dev->struct_mutex.
-        *
-        * Size: 4 bits for 16 fences + sign (for FENCE_REG_NONE)
         */
-       signed int fence_reg:5;
+       signed int fence_reg:I915_MAX_NUM_FENCE_BITS;
 
        /**
         * Advice: are the backing pages purgeable?
 
        struct drm_i915_private *dev_priv = dev->dev_private;
        int i;
 
-       for (i = 0; i < 16; i++) {
+       for (i = 0; i < dev_priv->num_fence_regs; i++) {
                struct drm_i915_fence_reg *reg = &dev_priv->fence_regs[i];
                struct drm_i915_gem_object *obj = reg->obj;
 
        INIT_LIST_HEAD(&dev_priv->mm.gtt_list);
        for (i = 0; i < I915_NUM_RINGS; i++)
                init_ring_lists(&dev_priv->ring[i]);
-       for (i = 0; i < 16; i++)
+       for (i = 0; i < I915_MAX_NUM_FENCES; i++)
                INIT_LIST_HEAD(&dev_priv->fence_regs[i].lru_list);
        INIT_DELAYED_WORK(&dev_priv->mm.retire_work,
                          i915_gem_retire_work_handler);