Re: [igt-dev] [PATCH i-g-t] tests/kms_dp_dsc: Force a full modeset when we force dsc enable

[Imre Deak <imre.deak@intel.com>]

On Wed, Apr 03, 2019 at 01:49:44PM -0700, Manasi Navare wrote:
> [...]
> Currently we have inh i915_dsc_fec_support_show:
> DSC_enabled:
> DSC_sink_support:
> FEC_sink_support:

Yes, and after the kernel change you'll have an additional
  
  Force DSC enable: yes/no

line here.

> And this node we open as a read only first and then as write node and
> force_dsc_enable() from IGT just writes a 1 to this, so you are saying
> that in the kernel _write() node, I accept this and write to
> force_dsc_enable entry in this file instead of rewriting the whole
> file?

I'm not sure what you mean. Currently "1" or "0" is written to the
debugfs file which will set intel_dp->force_dsc_enable. This doesn't
need to be changed at all, no need to rewrite the whole file.

> So in IGT also I will have to parse the file and write 1 for
> force_dsc_enable entry?

You can get the original value of it similarly to how it's done already
for 'DSC_Sink_Support', by reading the file and doing

	strstr(buf, "Force DSC enable: yes");

on the content.

> I still cant figure out how the restore() function work, we write the
> stored_values and write for each of the entries in the file? And then
> in the kernel debugfs_write, get these and write back to each entry?

Only force_dsc_enable need to be restored, the only value that you
change by writing to the debugfs file. All the rest are calculated
values that you don't need to care about.

--Imre
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