[Intel-gfx] [RFC PATCH i-g-t] lib/i915/perf: Fix non-card0 processing

[Janusz Krzysztofik]

Hi Lionel,

On poniedziałek, 3 maja 2021 09:07:09 CEST Lionel Landwerlin wrote:
> On 30/04/2021 19:18, Janusz Krzysztofik wrote:
> > IGT i915/perf library functions now always operate on sysfs perf
> > attributes of card0 device node, no matter which DRM device fd a user
> > passes.  The intention was to always switch to primary device node if
> > a user passes a render device node fd, but that breaks handling of
> > non-card0 devices.
> >
> > Instead of forcibly using DRM device minor number 0 when opening a
> > device sysfs area, convert device minor number of a user passed device
> > fd to the minor number of respective primary (cardX) device node.
> >
> > Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
> > ---
> >   lib/i915/perf.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/i915/perf.c b/lib/i915/perf.c
> > index 56d5c0b3a..336824df7 100644
> > --- a/lib/i915/perf.c
> > +++ b/lib/i915/perf.c
> > @@ -376,8 +376,8 @@ open_master_sysfs_dir(int drm_fd)
> >   	if (fstat(drm_fd, &st) || !S_ISCHR(st.st_mode))
> >                   return -1;
> >   
> > -        snprintf(path, sizeof(path), "/sys/dev/char/%d:0",
> > -                 major(st.st_rdev));
> > +        snprintf(path, sizeof(path), "/sys/dev/char/%d:%d",
> > +                 major(st.st_rdev), minor(st.st_rdev) & ~128);
> 
> 
> Isn't it minor(st.st_rdev) & 0xff ? 

Did you mean 0x7f?

> or even 0x3f ?
> 
> Looks like /dev/dri/controlD64 can exist too.

Not any longer, see commit 0d49f303e8a7 ("drm: remove all control node code").

However, my approach of applying a mask is oversimplified.  Minor numbers for 
different node types (primary and render) are handled separately.  I'm going 
to propose a method similar to that implemented in igt_debugfs_path().

Thanks,
Janusz


> 
> 
> -Lionel
> 
> 
> >   
> >   	return open(path, O_DIRECTORY);
> >   }
> 
> 
>