drm/i915: Mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch
cases where we are expecting to fall through.

This patch fixes the following warnings:

drivers/gpu/drm/i915/gem/i915_gem_mman.c: In function ‘i915_gem_fault’:
drivers/gpu/drm/i915/gem/i915_gem_mman.c:342:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
   if (!i915_terminally_wedged(i915))
      ^
drivers/gpu/drm/i915/gem/i915_gem_mman.c:345:2: note: here
  case -EAGAIN:
  ^~~~

drivers/gpu/drm/i915/gem/i915_gem_pages.c: In function ‘i915_gem_object_map’:
./include/linux/compiler.h:78:22: warning: this statement may fall through [-Wimplicit-fallthrough=]
 # define unlikely(x) __builtin_expect(!!(x), 0)
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~
./include/asm-generic/bug.h:136:2: note: in expansion of macro ‘unlikely’
  unlikely(__ret_warn_on);     \
  ^~~~~~~~
drivers/gpu/drm/i915/i915_utils.h:49:25: note: in expansion of macro ‘WARN’
 #define MISSING_CASE(x) WARN(1, "Missing case (%s == %ld)\n", \
                         ^~~~
drivers/gpu/drm/i915/gem/i915_gem_pages.c:270:3: note: in expansion of macro ‘MISSING_CASE’
   MISSING_CASE(type);
   ^~~~~~~~~~~~
drivers/gpu/drm/i915/gem/i915_gem_pages.c:272:2: note: here
  case I915_MAP_WB:
  ^~~~

drivers/gpu/drm/i915/i915_gpu_error.c: In function ‘error_record_engine_registers’:
./include/linux/compiler.h:78:22: warning: this statement may fall through [-Wimplicit-fallthrough=]
 # define unlikely(x) __builtin_expect(!!(x), 0)
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~
./include/asm-generic/bug.h:136:2: note: in expansion of macro ‘unlikely’
  unlikely(__ret_warn_on);     \
  ^~~~~~~~
drivers/gpu/drm/i915/i915_utils.h:49:25: note: in expansion of macro ‘WARN’
 #define MISSING_CASE(x) WARN(1, "Missing case (%s == %ld)\n", \
                         ^~~~
drivers/gpu/drm/i915/i915_gpu_error.c:1196:5: note: in expansion of macro ‘MISSING_CASE’
     MISSING_CASE(engine->id);
     ^~~~~~~~~~~~
drivers/gpu/drm/i915/i915_gpu_error.c:1197:4: note: here
    case RCS0:
    ^~~~

drivers/gpu/drm/i915/display/intel_dp.c: In function ‘intel_dp_get_fia_supported_lane_count’:
./include/linux/compiler.h:78:22: warning: this statement may fall through [-Wimplicit-fallthrough=]
 # define unlikely(x) __builtin_expect(!!(x), 0)
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~
./include/asm-generic/bug.h:136:2: note: in expansion of macro ‘unlikely’
  unlikely(__ret_warn_on);     \
  ^~~~~~~~
drivers/gpu/drm/i915/i915_utils.h:49:25: note: in expansion of macro ‘WARN’
 #define MISSING_CASE(x) WARN(1, "Missing case (%s == %ld)\n", \
                         ^~~~
drivers/gpu/drm/i915/display/intel_dp.c:233:3: note: in expansion of macro ‘MISSING_CASE’
   MISSING_CASE(lane_info);
   ^~~~~~~~~~~~
drivers/gpu/drm/i915/display/intel_dp.c:234:2: note: here
  case 1:
  ^~~~

drivers/gpu/drm/i915/display/intel_display.c: In function ‘check_digital_port_conflicts’:
  CC [M]  drivers/gpu/drm/nouveau/nvkm/engine/disp/cursgv100.o
drivers/gpu/drm/i915/display/intel_display.c:12043:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
    if (WARN_ON(!HAS_DDI(to_i915(dev))))
       ^
drivers/gpu/drm/i915/display/intel_display.c:12046:3: note: here
   case INTEL_OUTPUT_DP:
   ^~~~

Also, notice that the Makefile is modified to stop ignoring
fall-through warnings. The -Wimplicit-fallthrough option
will be enabled globally in v5.3.

Warning level 3 was used: -Wimplicit-fallthrough=3

This patch is part of the ongoing efforts to enable
-Wimplicit-fallthrough.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

2 files changed, 2 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index 391621ee3cbb..39a661927d8e 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -341,7 +341,7 @@ err:
 		 */
 		if (!i915_terminally_wedged(i915))
 			return VM_FAULT_SIGBUS;
-		/* else: fall through */
+		/* else, fall through */
 	case -EAGAIN:
 		/*
 		 * EAGAIN means the gpu is hung and we'll wait for the error
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
index b36ad269f4ea..65eb430cedba 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -268,7 +268,7 @@ static void *i915_gem_object_map(const struct drm_i915_gem_object *obj,
 	switch (type) {
 	default:
 		MISSING_CASE(type);
-		/* fallthrough to use PAGE_KERNEL anyway */
+		/* fallthrough - to use PAGE_KERNEL anyway */
 	case I915_MAP_WB:
 		pgprot = PAGE_KERNEL;
 		break;