From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D8002282F10; Mon, 4 May 2026 17:29:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777915745; cv=none; b=KVBumf8RmU6oL1zagCG5Z/WfFJlkA0wV5KS+xDKPQa6KU+tJCKsfA4BmOwaSaXtSm1AuYazJs1xktwjlDpUbAM7UKRTUbU/ZmJIvKzaMkuMYrFFIx3+41uVKNVCBwvmQXbrV7MyWXHE+8NnNiicnnIbWJiG86ntiBxNxIhM17a0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777915745; c=relaxed/simple; bh=rivBCjMAfflXwt1qFSOeJbPBfqzxRqu5f/V7lLMrAdw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=j1d80GPgS2aP1Jkg/Yp57yATQ1nLmTTjgNDYkjQH5KoJxwip+Sv5Whc8eB2bQ/CGApBwinOUYOMCRitP0VP05ZiuAgRnr1i95lap/m4xmC4Ycr/ytqidUST4JxJk1IpOib6DwjO7YFehJAgjYtI7+HNXj11H0nhngauqW3bDix4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=JzbQ7tJZ; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="JzbQ7tJZ" Received: from killaraus.ideasonboard.com (2001-14ba-703d-e500--2a1.rev.dnainternet.fi [IPv6:2001:14ba:703d:e500::2a1]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 090C98F; Mon, 4 May 2026 19:28:58 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1777915738; bh=rivBCjMAfflXwt1qFSOeJbPBfqzxRqu5f/V7lLMrAdw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JzbQ7tJZxf25NmYoqnYYam36yrgF5W1S0esLviwPX3bd/5Mc0bFy+PH/bRQ4stv3S FBdYYCtlb6xIQKkVEDz1oVs7DUsA4p5Kd6S8crYGwbHzx8bQXSE0xvoX3ShNrz9HWC l1Y5cDT3YyIXLT/QrM/SKMW47xH1ATHdciNqvkps= Date: Mon, 4 May 2026 20:28:58 +0300 From: Laurent Pinchart To: Maxime Ripard Cc: Maarten Lankhorst , Thomas Zimmermann , David Airlie , Simona Vetter , Jonathan Corbet , Shuah Khan , Dmitry Baryshkov , Jyri Sarha , Tomi Valkeinen , Andrzej Hajda , Neil Armstrong , Robert Foss , Jonas Karlman , Jernej Skrabec , Simon Ser , Harry Wentland , Melissa Wen , Sebastian Wick , Alex Hung , Jani Nikula , Rodrigo Vivi , Joonas Lahtinen , Tvrtko Ursulin , Chen-Yu Tsai , Samuel Holland , Dave Stevenson , =?utf-8?B?TWHDrXJh?= Canal , Raspberry Pi Kernel Maintenance , dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Daniel Stone , intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev Subject: Re: [PATCH v3 12/20] drm/crtc: Add new atomic_create_state callback Message-ID: <20260504172858.GO1344263@killaraus.ideasonboard.com> References: <20260424-drm-mode-config-init-v3-0-8b68d9db0d8b@kernel.org> <20260424-drm-mode-config-init-v3-12-8b68d9db0d8b@kernel.org> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260424-drm-mode-config-init-v3-12-8b68d9db0d8b@kernel.org> On Fri, Apr 24, 2026 at 12:18:52PM +0200, Maxime Ripard wrote: > Commit 47b5ac7daa46 ("drm/atomic: Add new atomic_create_state callback > to drm_private_obj") introduced a new pattern for allocating drm object > states. > > Instead of relying on the reset() callback, it created a new > atomic_create_state hook. This is helpful because reset is a bit > overloaded: it's used to create the initial software state, reset it, > but also reset the hardware. > > It can also be used either at probe time, to create the initial state > and possibly reset the hardware to an expected default, but also during > suspend/resume. > > Both these cases come with different expectations too: during the > initialization, we want to initialize all states, but during > suspend/resume, drm_private_states for example are expected to be kept > around. > > reset() also isn't fallible, which makes it harder to handle > initialization errors properly. This is only really relevant for some > drivers though, since all the helpers for reset only create a new > state, and don't touch the hardware at all. > > It was thus decided to create a new hook that would allocate and > initialize a pristine state without any side effect: > atomic_create_state to untangle a bit some of it, and to separate the > initialization with the actual reset one might need during a > suspend/resume. > > Continue the transition to the new pattern with CRTCs. > > Reviewed-by: Dmitry Baryshkov > Signed-off-by: Maxime Ripard > --- > drivers/gpu/drm/drm_atomic_state_helper.c | 47 +++++++++++++++++++++++++++++++ > drivers/gpu/drm/drm_mode_config.c | 21 +++++++++++++- > include/drm/drm_atomic_state_helper.h | 4 +++ > include/drm/drm_crtc.h | 16 +++++++++++ > 4 files changed, 87 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c > index 9cd8550cabb7..b7da134c8c50 100644 > --- a/drivers/gpu/drm/drm_atomic_state_helper.c > +++ b/drivers/gpu/drm/drm_atomic_state_helper.c > @@ -103,10 +103,32 @@ __drm_atomic_helper_crtc_reset(struct drm_crtc *crtc, > > crtc->state = crtc_state; > } > EXPORT_SYMBOL(__drm_atomic_helper_crtc_reset); > > +/** > + * __drm_atomic_helper_crtc_create_state - initializes crtc state "Initialize a CRTC state" The name of the function is misleading ("*_create_*" while you state it performs initialization). > + * @crtc: crtc object > + * @state: new state to initialize > + * > + * Initializes the newly allocated @state, usually required when > + * initializing the drivers. > + * > + * @state is assumed to be zeroed. > + * > + * This is useful for drivers that subclass @drm_crtc_state. > + */ > +void __drm_atomic_helper_crtc_create_state(struct drm_crtc *crtc, > + struct drm_crtc_state *state) > +{ > + __drm_atomic_helper_crtc_state_init(state, crtc); > + > + if (drm_dev_has_vblank(crtc->dev)) > + drm_crtc_vblank_reset(crtc); This is confusing to me (at least before reading the rest of the series), and itn't mentioned in the function documentation or in the commit message. Furthermore, __drm_atomic_helper_crtc_create_state() is later used in tidss_crtc_create_state(), which is the drm_crtc_funcs.atomic_create_state() implementation of the tidss driver. The atomic_create_state documentation states that "This callback must have no side effect", and drm_crtc_vblank_reset() has side effects. > +} > +EXPORT_SYMBOL(__drm_atomic_helper_crtc_create_state); > + > /** > * drm_atomic_helper_crtc_reset - default &drm_crtc_funcs.reset hook for CRTCs > * @crtc: drm CRTC > * > * Resets the atomic state for @crtc by freeing the state pointer (which might > @@ -122,10 +144,35 @@ void drm_atomic_helper_crtc_reset(struct drm_crtc *crtc) > > __drm_atomic_helper_crtc_reset(crtc, crtc_state); > } > EXPORT_SYMBOL(drm_atomic_helper_crtc_reset); > > +/** > + * drm_atomic_helper_crtc_create_state - default &drm_crtc_funcs.atomic_create_state hook for crtcs Same comment as in patch 10/20. > + * @crtc: crtc object > + * > + * Initializes a pristine @drm_crtc_state. "Allocate and initialize ..." > + * > + * This is useful for drivers that don't subclass @drm_crtc_state. > + * > + * RETURNS: > + * Pointer to new crtc state, or ERR_PTR on failure. > + */ > +struct drm_crtc_state *drm_atomic_helper_crtc_create_state(struct drm_crtc *crtc) > +{ > + struct drm_crtc_state *state; > + > + state = kzalloc_obj(*state); > + if (!state) > + return ERR_PTR(-ENOMEM); > + > + __drm_atomic_helper_crtc_create_state(crtc, state); > + > + return state; > +} > +EXPORT_SYMBOL(drm_atomic_helper_crtc_create_state); > + > /** > * __drm_atomic_helper_crtc_duplicate_state - copy atomic CRTC state > * @crtc: CRTC object > * @state: atomic CRTC state > * > diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c > index 10b7815cbe48..182d9a8104e7 100644 > --- a/drivers/gpu/drm/drm_mode_config.c > +++ b/drivers/gpu/drm/drm_mode_config.c > @@ -196,10 +196,26 @@ static int drm_mode_config_plane_create_state(struct drm_plane *plane) > plane->state = plane_state; > > return 0; > } > > +static int drm_mode_config_crtc_create_state(struct drm_crtc *crtc) > +{ > + struct drm_crtc_state *crtc_state; > + > + if (!crtc->funcs->atomic_create_state) > + return 0; > + > + crtc_state = crtc->funcs->atomic_create_state(crtc); > + if (IS_ERR(crtc_state)) > + return PTR_ERR(crtc_state); > + > + crtc->state = crtc_state; > + > + return 0; > +} > + > /** > * drm_mode_config_reset - call ->reset callbacks > * @dev: drm device > * > * This functions calls all the crtc's, encoder's and connector's ->reset > @@ -227,13 +243,16 @@ void drm_mode_config_reset(struct drm_device *dev) > plane->funcs->reset(plane); > else if (plane->funcs->atomic_create_state) > drm_mode_config_plane_create_state(plane); > } > > - drm_for_each_crtc(crtc, dev) > + drm_for_each_crtc(crtc, dev) { > if (crtc->funcs->reset) > crtc->funcs->reset(crtc); > + else if (crtc->funcs->atomic_create_state) > + drm_mode_config_crtc_create_state(crtc); > + } > > drm_for_each_encoder(encoder, dev) > if (encoder->funcs && encoder->funcs->reset) > encoder->funcs->reset(encoder); > > diff --git a/include/drm/drm_atomic_state_helper.h b/include/drm/drm_atomic_state_helper.h > index e7fbbfdc5d69..129762b99de6 100644 > --- a/include/drm/drm_atomic_state_helper.h > +++ b/include/drm/drm_atomic_state_helper.h > @@ -43,10 +43,14 @@ struct drm_device; > void __drm_atomic_helper_crtc_state_init(struct drm_crtc_state *state, > struct drm_crtc *crtc); > void __drm_atomic_helper_crtc_reset(struct drm_crtc *crtc, > struct drm_crtc_state *state); > void drm_atomic_helper_crtc_reset(struct drm_crtc *crtc); > +void __drm_atomic_helper_crtc_create_state(struct drm_crtc *crtc, > + struct drm_crtc_state *state); > +struct drm_crtc_state * > +drm_atomic_helper_crtc_create_state(struct drm_crtc *crtc); > void __drm_atomic_helper_crtc_duplicate_state(struct drm_crtc *crtc, > struct drm_crtc_state *state); > struct drm_crtc_state * > drm_atomic_helper_crtc_duplicate_state(struct drm_crtc *crtc); > void __drm_atomic_helper_crtc_destroy_state(struct drm_crtc_state *state); > diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h > index 312fc1e745d2..41ea6eadf36f 100644 > --- a/include/drm/drm_crtc.h > +++ b/include/drm/drm_crtc.h > @@ -636,10 +636,26 @@ struct drm_crtc_funcs { > * 0 on success or a negative error code on failure. > */ > int (*set_property)(struct drm_crtc *crtc, > struct drm_property *property, uint64_t val); > > + /** > + * @atomic_create_state: > + * > + * Allocates a pristine, initialized, state for the CRTC object s/Allocates/Allocate/ > + * and returns it. This callback must have no side effects: in > + * particular, the returned state must not be assigned to the > + * object's state pointer and it must not affect the hardware > + * state. > + * > + * RETURNS: > + * > + * A new, pristine, CRTC state instance or an error pointer > + * on failure. > + */ > + struct drm_crtc_state *(*atomic_create_state)(struct drm_crtc *crtc); > + > /** > * @atomic_duplicate_state: > * > * Duplicate the current atomic state for this CRTC and return it. > * The core and helpers guarantee that any atomic state duplicated with -- Regards, Laurent Pinchart