linux-kernel - Re: [PATCH v2 1/3] drm/modes: introduce drm_mode_validate

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Message-ID: <20241126-tentacled-busy-catfish-c451fc@houat>
Date: Tue, 26 Nov 2024 16:49:50 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Jani Nikula <jani.nikula@...ux.intel.com>
Cc: Sean Nyekjaer <sean@...nix.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Chen-Yu Tsai <wens@...e.org>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, 
	Yannick Fertre <yannick.fertre@...s.st.com>, Raphael Gallais-Pou <raphael.gallais-pou@...s.st.com>, 
	Philippe Cornu <philippe.cornu@...s.st.com>, Maxime Coquelin <mcoquelin.stm32@...il.com>, 
	Alexandre Torgue <alexandre.torgue@...s.st.com>, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev, 
	linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH v2 1/3] drm/modes: introduce drm_mode_validate_mode()
 helper function

On Tue, Nov 26, 2024 at 02:24:12PM +0200, Jani Nikula wrote:
> On Tue, 26 Nov 2024, Maxime Ripard <mripard@...nel.org> wrote:
> > On Tue, Nov 26, 2024 at 12:16:34PM +0200, Jani Nikula wrote:
> >> On Mon, 25 Nov 2024, Maxime Ripard <mripard@...nel.org> wrote:
> >> > I wonder about the naming though (and prototype). I doesn't really
> >> > validates a mode, but rather makes sure that a given rate is a good
> >> > approximation of a pixel clock. So maybe something like
> >> > drm_mode_check_pixel_clock?
> >> 
> >> Quoting myself from a few weeks back:
> >> 
> >> """
> >> Random programming thought of the day: "check" is generally a terrible
> >> word in a function name.
> >> 
> >> Checking stuff is great, but what do you expect to happen if the check
> >> passes/fails? Do you expect the function to return on fail, or throw an
> >> exception? Or just log about it? If you return a value, what should the
> >> return value mean? It's hard to know without looking it up.
> >> 
> >> Prefer predicates instead, is_stuff_okay() is better than
> >> check_stuff(). Or assert_stuff() if you don't return on failures.
> >> """
> >
> > Both is_stuff_okay() or assert_stuff() return a boolean in my mind. If
> > you want to return a mode status enum, I don't think they are better
> > names.
> 
> Most functions returning enum drm_mode_status are called
> something_something_mode_valid(). Not check something.

But it doesn't check whether the mode is valid or not. It checks whether
a given clock rate is within reasonable tolerance from the expected
pixel clock.

Maxime

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