Re: [bug report] drm/dp: annotate implicit fall throughs

2020-08-31 Thread Dan Carpenter 
On Fri, Aug 28, 2020 at 12:53:32PM +0300, Jani Nikula wrote:
> On Tue, 25 Aug 2020, Dan Carpenter  wrote:
> > 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],
> >468const 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...
> 
> Won't that be unreachable as well?
> 
> Maybe just add the default label to switch (bpc)?

A default switch is going to be unreachable as well...  But adding a
return 0 is the older more traditional ways way of marking these so
people and checkers are used to it.

regards,
dan carpenter

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Re: [bug report] drm/dp: annotate implicit fall throughs

2020-08-28 Thread Jani Nikula 
On Tue, 25 Aug 2020, Dan Carpenter  wrote:
> 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],
>468const 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...

Won't that be unreachable as well?

Maybe just add the default label to switch (bpc)?

BR,
Jani.


>
>496  default:
>497  return 0;
>498  }
>499  }
>
> regards,
> dan carpenter
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-- 
Jani Nikula, Intel Open Source Graphics Center
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[bug report] drm/dp: annotate implicit fall throughs

2020-08-25 Thread Dan Carpenter 
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],
   468const 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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