On Mon, Dec 15, 2025 at 09:46:24AM +0200, Luca Coelho wrote:
> On Thu, 2025-11-27 at 19:49 +0200, Imre Deak wrote:
> > Factor out align_max_sink_dsc_input_bpp(), also used later for computing
> > the maximum DSC input BPP limit.
> >
> > Signed-off-by: Imre Deak <[email protected]>
> > ---
> > drivers/gpu/drm/i915/display/intel_dp.c | 28 ++++++++++++++++---------
> > 1 file changed, 18 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 000fccc39a292..dcb9bc11e677b 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -1893,12 +1893,27 @@ int intel_dp_dsc_max_src_input_bpc(struct
> > intel_display *display)
> > return intel_dp_dsc_min_src_input_bpc();
> > }
> >
> > +static int align_max_sink_dsc_input_bpp(const struct intel_connector
> > *connector,
> > + int max_pipe_bpp)
> > +{
> > + u8 dsc_bpc[3];
>
> I think it's safer to use the '= {}' we had before, because that zeroes
> the array, so in case of any stack leaks, you won't leak aleatory parts
> of the memory. In this case it's only 3 bytes, so hardly anything
> important could leak, but anyway.
As for any other variable I don't see any reason for initializing it, if
it will be initialized before its first use. It will be initialized
before its first use by drm_dp_dsc_sink_supported_input_bpcs().
> Also, since this is 3 bytes long, it's theoretically better to have it
> at the end of the stack declarations.
The compiler is free to reorder the allocation order on the stack and
is expected to that for optimal alignment.
> > + int num_bpc;
> > + int i;
> > +
> > + num_bpc = drm_dp_dsc_sink_supported_input_bpcs(connector->dp.dsc_dpcd,
> > + dsc_bpc);
> > + for (i = 0; i < num_bpc; i++) {
> > + if (dsc_bpc[i] * 3 <= max_pipe_bpp)
> > + return dsc_bpc[i] * 3;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > int intel_dp_dsc_compute_max_bpp(const struct intel_connector *connector,
> > u8 max_req_bpc)
> > {
> > struct intel_display *display = to_intel_display(connector);
> > - int i, num_bpc;
> > - u8 dsc_bpc[3] = {};
> > int dsc_max_bpc;
> >
> > dsc_max_bpc = intel_dp_dsc_max_src_input_bpc(display);
> > @@ -1908,14 +1923,7 @@ int intel_dp_dsc_compute_max_bpp(const struct
> > intel_connector *connector,
> >
> > dsc_max_bpc = min(dsc_max_bpc, max_req_bpc);
> >
> > - num_bpc = drm_dp_dsc_sink_supported_input_bpcs(connector->dp.dsc_dpcd,
> > - dsc_bpc);
> > - for (i = 0; i < num_bpc; i++) {
> > - if (dsc_max_bpc >= dsc_bpc[i])
> > - return dsc_bpc[i] * 3;
> > - }
> > -
> > - return 0;
> > + return align_max_sink_dsc_input_bpp(connector, dsc_max_bpc * 3);
> > }
> >
> > static int intel_dp_source_dsc_version_minor(struct intel_display *display)
