panfrost: Check for NULL surface in places

Fixes a bunch of NULL dereferences, although it does cause GPU faults of
course.

This is caused by color buffers masked out in MRT, which we'll
eventually have to solve the right way... one thing at a time.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>

src/gallium/drivers/panfrost/pan_blend_cso.c

@@ -212,7 +212,7 @@ panfrost_get_blend_for_context(struct panfrost_context *ctx, unsigned rti)
         struct pipe_framebuffer_state *fb = &ctx->pipe_framebuffer;
         enum pipe_format fmt = PIPE_FORMAT_R8G8B8A8_UNORM;
 
-        if (fb->nr_cbufs > rti)
+        if ((fb->nr_cbufs > rti) && fb->cbufs[rti])
                 fmt = fb->cbufs[rti]->format;
 
         /* Grab the blend state */

src/gallium/drivers/panfrost/pan_context.c

@@ -1213,11 +1213,10 @@ panfrost_emit_for_draw(struct panfrost_context *ctx, bool with_vertex_data)
 
                         struct midgard_blend_rt rts[4];
 
-                        /* TODO: MRT */
-
-                        for (unsigned i = 0; i < 1; ++i) {
+                        for (unsigned i = 0; i < ctx->pipe_framebuffer.nr_cbufs; ++i) {
                                 bool is_srgb =
                                         (ctx->pipe_framebuffer.nr_cbufs > i) &&
+                                        (ctx->pipe_framebuffer.cbufs[i]) &&
                                         util_format_is_srgb(ctx->pipe_framebuffer.cbufs[i]->format);
 
                                 rts[i].flags = blend_count;

src/gallium/drivers/panfrost/pan_fragment.c

@@ -35,6 +35,9 @@ panfrost_initialize_surface(
                 struct panfrost_job *batch,
                 struct pipe_surface *surf)
 {
+        if (!surf)
+                return;
+
         unsigned level = surf->u.tex.level;
         struct panfrost_resource *rsrc = pan_resource(surf->texture);
 

src/gallium/drivers/panfrost/pan_mfbd.c

@@ -403,6 +403,10 @@ panfrost_mfbd_fragment(struct panfrost_context *ctx, bool has_draws)
 
         for (int cb = 0; cb < ctx->pipe_framebuffer.nr_cbufs; ++cb) {
                 struct pipe_surface *surf = ctx->pipe_framebuffer.cbufs[cb];
+
+                if (!surf)
+                        continue;
+
                 unsigned bpp = util_format_get_blocksize(surf->format);
 
                 panfrost_mfbd_set_cbuf(&rts[cb], surf);

src/gallium/drivers/panfrost/pan_resource.c

@@ -507,7 +507,10 @@ panfrost_transfer_map(struct pipe_context *pctx,
         bool is_bound = false;
 
         for (unsigned c = 0; c < fb->nr_cbufs; ++c) {
-                is_bound |= fb->cbufs[c]->texture == resource;
+                /* If cbufs is NULL, we're definitely not bound here */
+
+                if (fb->cbufs[c])
+                        is_bound |= fb->cbufs[c]->texture == resource;
         }
 
         if (is_bound && (usage & PIPE_TRANSFER_READ)) {