Building legacy DRM drivers on -current, and the fallout

[Hauke Fath <hf%spg.tu-darmstadt.de@localhost>]

All,

I need to build a kernel for a Thinkpad T23, which sports an S3 Savage.

Enabling the legacy DRM drivers on -current (and disabling the DRMKMS 
ones) leads to fall-out for r128drm(4) and savagedrm(4):


#   compile  T23/r128_cce.o
/u/netbsd-builds/developer/i386/tools/bin/i486--netbsdelf-gcc 
-msoft-float -mno-mmx -mno-sse -mno-avx -mindirect-branch=thunk 
-mindirect-branch-register -ffreestanding -fno-zero-initialized-in-bss 
-fno-delete-null-pointer-checks
/public/netbsd-developer/sys/external/bsd/drm/dist/shared-core/r128_cce.c: 
In function 'r128_do_init_cce':
/public/netbsd-developer/sys/external/bsd/drm/dist/shared-core/r128_cce.c:415:2: 
error: case label does not reduce to an integer constant
  case R128_PM4_64BM_64VCBM_64INDBM:
  ^~~~
/public/netbsd-developer/sys/external/bsd/drm/dist/shared-core/r128_cce.c:416:2: 
error: case label does not reduce to an integer constant
  case R128_PM4_64PIO_64VCPIO_64INDPIO:
  ^~~~

*** Failed target:  r128_cce.o

% /<8>dist/shared-core > egrep 
'R128_PM4_64BM_64VCBM_64INDBM|R128_PM4_64PIO_64VCPIO_64INDPIO' *
r128_cce.c:         (init->cce_mode != R128_PM4_64BM_64VCBM_64INDBM)) {
r128_cce.c:     case R128_PM4_64BM_64VCBM_64INDBM:
r128_cce.c:     case R128_PM4_64PIO_64VCPIO_64INDPIO:
r128_drv.h:#    define R128_PM4_64BM_64VCBM_64INDBM     (8  << 28)
r128_drv.h:#    define R128_PM4_64PIO_64VCPIO_64INDPIO  (15 << 28)
%

-- These look constant to me, and of integer type, so I am not sure what 
gcc is trying to flag here, and what to do about it.


"savage_state.c", OTOH, triggered several "warning: this statement may 
fall through [-Wimplicit-fallthrough=]". The attached patch deals with 
that - the flagged fallthroughs look legit to me.

Okay to commit?

Cheerio,
hauke

--
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Index: savage_state.c
===================================================================
RCS file: /cvsroot/src/sys/external/bsd/drm/dist/shared-core/savage_state.c,v
retrieving revision 1.4
diff -u -u -r1.4 savage_state.c
--- savage_state.c	23 Jun 2009 04:42:01 -0000	1.4
+++ savage_state.c	22 Jul 2019 15:20:46 -0000
@@ -297,6 +297,7 @@
 	case SAVAGE_PRIM_TRILIST_201:
 		reorder = 1;
 		prim = SAVAGE_PRIM_TRILIST;
+		/* FALLTHROUGH */
 	case SAVAGE_PRIM_TRILIST:
 		if (n % 3 != 0) {
 			DRM_ERROR("wrong number of vertices %u in TRILIST\n",
@@ -434,6 +435,7 @@
 	case SAVAGE_PRIM_TRILIST_201:
 		reorder = 1;
 		prim = SAVAGE_PRIM_TRILIST;
+		/* FALLTHROUGH */
 	case SAVAGE_PRIM_TRILIST:
 		if (n % 3 != 0) {
 			DRM_ERROR("wrong number of vertices %u in TRILIST\n",
@@ -555,6 +557,7 @@
 	case SAVAGE_PRIM_TRILIST_201:
 		reorder = 1;
 		prim = SAVAGE_PRIM_TRILIST;
+		/* FALLTHROUGH */
 	case SAVAGE_PRIM_TRILIST:
 		if (n % 3 != 0) {
 			DRM_ERROR("wrong number of indices %u in TRILIST\n", n);
@@ -693,6 +696,7 @@
 	case SAVAGE_PRIM_TRILIST_201:
 		reorder = 1;
 		prim = SAVAGE_PRIM_TRILIST;
+		/* FALLTHROUGH */
 	case SAVAGE_PRIM_TRILIST:
 		if (n % 3 != 0) {
 			DRM_ERROR("wrong number of indices %u in TRILIST\n", n);
@@ -1060,7 +1064,7 @@
 				DMA_FLUSH();
 				return -EINVAL;
 			}
-			/* fall through */
+			/* FALLTHROUGH */
 		case SAVAGE_CMD_DMA_PRIM:
 		case SAVAGE_CMD_VB_PRIM:
 			if (!first_draw_cmd)