RE: [PATCH] drm/i915/display: Initialize phy and ch variables

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 03 Sep 2025, "Kahola, Mika" <mika.kahola@intel.com> wrote:
> Ok good to know. Let's just ignore this patch.

That said, all places that use bxt_port_to_phy_channel(),
vlv_dig_port_to_channel(), vlv_dig_port_to_phy(), vlv_pipe_to_channel(),
or vlv_pipe_to_phy() need *both* the phy and channel.

So I'm thinking you could add

struct {
        enum dpio_phy phy;
	enum dpio_channel channel;
} dpio_phy_channel;

and convert the above functions to always return that struct. It's small
enough to return as a whole. Something like:

	struct dpio_phy_channel phy_channel;

	phy_channel = bxt_port_to_phy_channel(display, port);

and

	phy_channel = vlv_dig_port_to_phy_channel(dig_port);

and

	phy_channel = vlv_pipe_to_phy_channel(pipe);

Then you can also do s/phy/phy_channel.phy/ and s/ch/phy_channel.ch/ as
cleanup (if it actually cleans things up, maybe not).

Bonus points if you can come up with a better name than
"phy_channel". ;)

With that, the interface gets reduced for vlv, and it's obvious to
static analyzers the stuff gets initialized. Win-win?


BR,
Jani.


>
> Thanks!
>
> -Mika-
>
>> -----Original Message-----
>> From: Jani Nikula <jani.nikula@linux.intel.com>
>> Sent: Wednesday, 3 September 2025 15.19
>> To: Kahola, Mika <mika.kahola@intel.com>; intel-gfx@lists.freedesktop.org; intel-xe@lists.freedesktop.org
>> Cc: Kahola, Mika <mika.kahola@intel.com>
>> Subject: Re: [PATCH] drm/i915/display: Initialize phy and ch variables
>> 
>> On Wed, 03 Sep 2025, Mika Kahola <mika.kahola@intel.com> wrote:
>> > phy and ch variables are potentially used uninitialized.
>> 
>> They're not, bxt_port_to_phy_channel() initializes them in all code paths.
>> 
>> > To make absolutely sure that these variables are not used
>> > uninitialized let's initialize these with known values as
>> > DPIO_PHY0 and DPIO_CH0, respectively.
>> >
>> > Signed-off-by: Mika Kahola <mika.kahola@intel.com>
>> > ---
>> >  drivers/gpu/drm/i915/display/intel_dpll_mgr.c | 4 ++--
>> >  1 file changed, 2 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
>> > b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
>> > index 8ea96cc524a1..45b67a3716e9 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
>> > +++ b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
>> > @@ -2174,8 +2174,8 @@ static bool bxt_ddi_pll_get_hw_state(struct intel_display *display,
>> >  	struct bxt_dpll_hw_state *hw_state = &dpll_hw_state->bxt;
>> >  	enum port port = (enum port)pll->info->id; /* 1:1 port->PLL mapping */
>> >  	intel_wakeref_t wakeref;
>> > -	enum dpio_phy phy;
>> > -	enum dpio_channel ch;
>> > +	enum dpio_phy phy = DPIO_PHY0;
>> > +	enum dpio_channel ch = DPIO_CH0;
>> >  	u32 val;
>> >  	bool ret;
>> 
>> --
>> Jani Nikula, Intel

-- 
Jani Nikula, Intel