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Date:   Tue, 30 Aug 2022 14:03:30 +0200
From:   Maxime Ripard <maxime@cerno.tech>
To:     Jani Nikula <jani.nikula@linux.intel.com>
Cc:     Geert Uytterhoeven <geert@linux-m68k.org>,
        Ben Skeggs <bskeggs@redhat.com>,
        David Airlie <airlied@linux.ie>, Chen-Yu Tsai <wens@csie.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Lyude Paul <lyude@redhat.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>,
        Karol Herbst <kherbst@redhat.com>,
        Noralf =?utf-8?Q?Tr=C3=B8nnes?= <noralf@tronnes.org>,
        Emma Anholt <emma@anholt.net>, Daniel Vetter <daniel@ffwll.ch>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
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        Mateusz Kwiatkowski <kfyatek+publicgit@gmail.com>
Subject: Re: [PATCH v2 14/41] drm/modes: Move named modes parsing to a
 separate function
Message-ID: <20220830120330.6f5f22d35gu7cbr3@houat>
References: <20220728-rpi-analog-tv-properties-v2-0-459522d653a7@cerno.tech>
 <20220728-rpi-analog-tv-properties-v2-14-459522d653a7@cerno.tech>
 <CAMuHMdV9wVgHFfwHoqtBoYzJDnjDmKTfaZkAKvTVKh1Y-2x1pA@mail.gmail.com>
 <87czcidnb8.fsf@intel.com>
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Hi,

On Tue, Aug 30, 2022 at 01:43:07PM +0300, Jani Nikula wrote:
> On Tue, 30 Aug 2022, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > On Mon, Aug 29, 2022 at 3:13 PM Maxime Ripard <maxime@cerno.tech> wrote:
> >> +#define STR_STRICT_EQ(str, len, cmp) \
> >> +       ((strlen(cmp) =3D=3D len) && !strncmp(str, cmp, len))
> >
> > This is not part of the move, but newly added.
>=20
> The same construct is also duplicated elsewhere in the series, and I
> kept being confused by it.

I'm not sure what is confusing, but I can add a comment if needed.

> The above is precisely the same as:
>=20
> 	str_has_prefix(str, cmp) =3D=3D len

Here, it's used to make sure we don't have a named mode starting with
either e, d, or D.

If I understood str_has_prefix() right, str_has_prefix("DUMB-MODE", "D")
=3D=3D strlen("DUMB-MODE") would return true, while it's actually what we
want to avoid.

It's also used indeed in drm_get_tv_mode_from_name(), where we try to
match a list of names with one passed as argument.

With drm_get_tv_mode_from_name("NSTC", strlen("NTSC")), we would end up
calling str_has_prefix("NTSC-J", "NTSC") =3D=3D strlen("NTSC-J") which would
work. However, we end up calling prefix not a prefix, but an entire
string we want to match against, which is very confusing to me too.

Maxime