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From: Thierry Reding <thierry.reding@gmail.com>
To: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Jani Nikula <jani.nikula@linux.intel.com>,
	daniel@ffwll.ch, airlied@linux.ie, alexander.deucher@amd.com,
	christian.koenig@amd.com, Xinhui.Pan@amd.com,
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	amd-gfx@lists.freedesktop.org,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	linux-tegra@vger.kernel.org, linux-sunxi@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 04/27] drm: Don't test for IRQ support in VBLANK ioctls
Date: Thu, 24 Jun 2021 14:03:39 +0200	[thread overview]
Message-ID: <YNR0m2DJsdIW3NAZ@orome.fritz.box> (raw)
In-Reply-To: <af21db75-584f-aec0-9659-d5386f27b4ea@suse.de>

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On Thu, Jun 24, 2021 at 11:07:57AM +0200, Thomas Zimmermann wrote:
> Hi
> 
> Am 24.06.21 um 10:51 schrieb Jani Nikula:
> > On Thu, 24 Jun 2021, Thomas Zimmermann <tzimmermann@suse.de> wrote:
> > > Hi
> > > 
> > > Am 24.06.21 um 10:06 schrieb Jani Nikula:
> > > > On Thu, 24 Jun 2021, Thomas Zimmermann <tzimmermann@suse.de> wrote:
> > > > > diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> > > > > index 3417e1ac7918..10fe16bafcb6 100644
> > > > > --- a/drivers/gpu/drm/drm_vblank.c
> > > > > +++ b/drivers/gpu/drm/drm_vblank.c
> > > > > @@ -1748,8 +1748,16 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
> > > > >    	unsigned int pipe_index;
> > > > >    	unsigned int flags, pipe, high_pipe;
> > > > > -	if (!dev->irq_enabled)
> > > > > -		return -EOPNOTSUPP;
> > > > > +#if defined(CONFIG_DRM_LEGACY)
> > > > > +	if  (unlikely(drm_core_check_feature(dev, DRIVER_LEGACY))) {
> > > > > +		if (!dev->irq_enabled)
> > > > > +			return -EOPNOTSUPP;
> > > > > +	} else /* if DRIVER_MODESET */
> > > > > +#endif
> > > > > +	{
> > > > > +		if (!drm_dev_has_vblank(dev))
> > > > > +			return -EOPNOTSUPP;
> > > > > +	}
> > > > 
> > > > Sheesh I hate this kind of inline #ifdefs.
> > > > 
> > > > Two alternate suggestions that I believe should be as just efficient:
> > > 
> > > Or how about:
> > > 
> > > static bool drm_wait_vblank_supported(struct drm_device *dev)
> > > 
> > > {
> > > 
> > > if defined(CONFIG_DRM_LEGACY)
> > > 	if  (unlikely(drm_core_check_feature(dev, DRIVER_LEGACY)))
> > > 
> > > 		return dev->irq_enabled;
> > > 
> > > #endif
> > > 	return drm_dev_has_vblank(dev);
> > > 
> > > }
> > > 
> > > 
> > > ?
> > > 
> > > It's inline, but still readable.
> > 
> > It's definitely better than the original, but it's unclear to me why
> > you'd prefer this over option 2) below. I guess the only reason I can
> > think of is emphasizing the conditional compilation. However,
> > IS_ENABLED() is widely used in this manner specifically to avoid inline
> > #if, and the compiler optimizes it away.
> 
> It's simply more readable to me as the condition is simpler. But option 2 is
> also ok.

Perhaps do something like this, then:

	if (IS_ENABLED(CONFIG_DRM_LEGACY)) {
		if (unlikely(drm_core_check_feature(dev, DRIVER_LEGACY)))
			return dev->irq_enabled;
	}

	return drm_dev_has_vblank(dev);

That's about just as readable as the variant involving the preprocessor
but has all the benefits of not using the preprocessor.

Thierry

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  parent reply	other threads:[~2021-06-24 12:01 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-24  7:28 [PATCH v3 00/27] Deprecate struct drm_device.irq_enabled Thomas Zimmermann
2021-06-24  7:28 ` [PATCH v3 01/27] drm/amdgpu: Track IRQ state in local device state Thomas Zimmermann
2021-06-24  7:28 ` [PATCH v3 02/27] drm/hibmc: Call drm_irq_uninstall() unconditionally Thomas Zimmermann
2021-06-24  7:28 ` [PATCH v3 03/27] drm/radeon: Track IRQ state in local device state Thomas Zimmermann
2021-06-24  7:28 ` [PATCH v3 04/27] drm: Don't test for IRQ support in VBLANK ioctls Thomas Zimmermann
2021-06-24  8:06   ` Jani Nikula
2021-06-24  8:19     ` Thomas Zimmermann
2021-06-24  8:28     ` Thomas Zimmermann
2021-06-24  8:51       ` Jani Nikula
2021-06-24  9:07         ` Thomas Zimmermann
2021-06-24 10:27           ` Liviu Dudau
2021-06-24 12:03           ` Thierry Reding [this message]
2021-06-24 12:36             ` Jani Nikula
2021-06-24 12:57               ` Thomas Zimmermann
2021-06-24  7:28 ` [PATCH v3 05/27] drm/armada: Don't set struct drm_device.irq_enabled Thomas Zimmermann
2021-06-24  7:28 ` [PATCH v3 06/27] drm/i915: Track IRQ state in local device state Thomas Zimmermann
2021-06-24  8:08   ` Jani Nikula
2021-06-24  7:28 ` [PATCH v3 07/27] drm/komeda: Don't set struct drm_device.irq_enabled Thomas Zimmermann
2021-06-24  7:28 ` [PATCH v3 08/27] drm/malidp: " Thomas Zimmermann
2021-06-24  7:28 ` [PATCH v3 09/27] drm/exynos: " Thomas Zimmermann
2021-06-24  7:28 ` [PATCH v3 10/27] drm/kirin: " Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 11/27] drm/imx: " Thomas Zimmermann
2021-06-24  8:25   ` Philipp Zabel
2021-06-24  7:29 ` [PATCH v3 12/27] drm/imx/dcss: " Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 13/27] drm/mediatek: " Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 14/27] drm/nouveau: " Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 15/27] drm/omapdrm: Track IRQ state in local device state Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 16/27] drm/rcar-du: Don't set struct drm_device.irq_enabled Thomas Zimmermann
2021-06-24 10:47   ` Laurent Pinchart
2021-06-24  7:29 ` [PATCH v3 17/27] drm/rockchip: " Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 18/27] drm/sti: " Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 19/27] drm/stm: " Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 20/27] drm/sun4i: " Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 21/27] drm/tegra: " Thomas Zimmermann
2021-06-24 12:04   ` Thierry Reding
2021-06-24  7:29 ` [PATCH v3 22/27] drm/tidss: Don't use " Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 23/27] drm/vc4: Don't set " Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 24/27] drm/vkms: " Thomas Zimmermann
2021-06-24 10:48   ` Laurent Pinchart
2021-06-24  7:29 ` [PATCH v3 25/27] drm/vmwgfx: " Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 26/27] drm/xlnx: " Thomas Zimmermann
2021-06-24  7:29 ` [PATCH v3 27/27] drm/zte: " Thomas Zimmermann

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