[Intel-gfx] [PATCH] drm/i915: Squeeze iommu status into debugfs/i915_capabilities

[Chris Wilson]

Quoting Martin Peres (2019-09-11 13:19:06)
> 
> 
> On 11/09/2019 14:46, Chris Wilson wrote:
> > There's no easy way of checking whether iommu is enabled for the GPU
> > (you can grep dmesg if you know the device, or you can grep
> > i915_gpu_info if that's available). We do have a central
> > i915_capabilities with the intent of listing such pertinent information,
> > so add the iommu status.
> > 
> > Suggested-by: Martin Peres <martin.peres at linux.intel.com>
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Martin Peres <martin.peres at linux.intel.com>
> > Cc: Tomi Sarvela <tomi.p.sarvela at intel.com>
> > Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_debugfs.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> > index 708855e051b5..e5835337f022 100644
> > --- a/drivers/gpu/drm/i915/i915_debugfs.c
> > +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> > @@ -61,11 +61,18 @@ static int i915_capabilities(struct seq_file *m, void *data)
> >       struct drm_i915_private *dev_priv = node_to_i915(m->private);
> >       const struct intel_device_info *info = INTEL_INFO(dev_priv);
> >       struct drm_printer p = drm_seq_file_printer(m);
> > +     const char *msg;
> >  
> >       seq_printf(m, "gen: %d\n", INTEL_GEN(dev_priv));
> >       seq_printf(m, "platform: %s\n", intel_platform_name(info->platform));
> >       seq_printf(m, "pch: %d\n", INTEL_PCH_TYPE(dev_priv));
> >  
> > +     msg = "n/a";
> 
> Here, "n/a" really means "kernel not compiled with IOMMU support".
> Should we find a wording better explaining this to users? Or are we
> going to tell users to check their dmesg for IOMMU messages and if there
> are none, it means either the kernel has not been compiled with support
> for it, or an option needs to be enabled in the bios, or the platform
> lacks support?

Users? This is debugfs, we should not be having users! :)
So whatever is convenient, just a string is slightly nicer for humans
than having -1, 0, 1.
-Chris