Hello Mathieu Malaterre,
The patch e9c0c874711b: "drm/dp: annotate implicit fall throughs"
from Jan 14, 2019, leads to the following static checker warning:
drivers/gpu/drm/drm_dp_helper.c:495 drm_dp_downstream_max_bpc()
warn: ignoring unreachable code.
drivers/gpu/drm/drm_dp_helper.c
467 int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
468 const u8 port_cap[4])
469 {
470 int type = port_cap[0] & DP_DS_PORT_TYPE_MASK;
471 bool detailed_cap_info = dpcd[DP_DOWNSTREAMPORT_PRESENT] &
472 DP_DETAILED_CAP_INFO_AVAILABLE;
473 int bpc;
474
475 if (!detailed_cap_info)
476 return 0;
477
478 switch (type) {
479 case DP_DS_PORT_TYPE_VGA:
480 case DP_DS_PORT_TYPE_DVI:
481 case DP_DS_PORT_TYPE_HDMI:
482 case DP_DS_PORT_TYPE_DP_DUALMODE:
483 bpc = port_cap[2] & DP_DS_MAX_BPC_MASK;
^^^^^^^^^^^^^^^^^^
This is 0x3.
484
485 switch (bpc) {
486 case DP_DS_8BPC:
487 return 8;
488 case DP_DS_10BPC:
489 return 10;
490 case DP_DS_12BPC:
491 return 12;
492 case DP_DS_16BPC:
493 return 16;
494 }
495 fallthrough;
This fallthrough is impossible. Probably the way to work around the
bogus warning is the change the fallthough to "return 0; /* impossible */"
otherwise the fallthrough is sort of misleading...
496 default:
497 return 0;
498 }
499 }
regards,
dan carpenter
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