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 B665E3E3DAE; Mon, 4 May 2026 16:52:32 +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=1777913554; cv=none; b=QTqQmI376WJsUhB2qAw92XC46B+5lhQI8K6Vk93/mIeQk5ExP+wxH0Bb9ACkvMPuAP4/ZZwsSXsydNATsd1/qDw7nwBvEJZ9mxQjPAqo1HQTQB2pvgc+dSQyOCCFgzksTr3Mmx1w0SX8VDmZl/inOulvpqdjLmOYpvYh2A7LsgQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777913554; c=relaxed/simple; bh=Zp02atCQOj7Mvz8FpD9o1Rib3JYiNwqY/fzhTQloymc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HuC9qCn8zxmRuReuyUZGGfs6stEEK+6Mlb+2cnTsciMvO10esPTirPr2ICGKq5B6x+zsyS9yF/nvr4I612feV46iIqBNSGqmK7DnCkftEwR/ozwffqzwnpqivO+1DwCexgQKXMqXZjipls212ZrvzEsfRxCTgQEU3PhYHbzHG+o= 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=apQMfJez; 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="apQMfJez" 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 4F3B79C; Mon, 4 May 2026 18:52:28 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1777913548; bh=Zp02atCQOj7Mvz8FpD9o1Rib3JYiNwqY/fzhTQloymc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=apQMfJezBXKACeI7uQn/oz/Lcn5MEWfk1oZq+4/QwXjK4nd490DgyWBu45eZIV78V oG6cukUKj4q26+bcvBlCyV4+vCJ07TZ41wfzmQ93Z73XT8XzHkRyqZY1OXQuMthKKo Uy+VcIEaS1+FAh3h5pLW3a03re+ils9QLAHjOAl8= Date: Mon, 4 May 2026 19:52:29 +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 10/20] drm/plane: Add new atomic_create_state callback Message-ID: <20260504165229.GM1344263@killaraus.ideasonboard.com> References: <20260424-drm-mode-config-init-v3-0-8b68d9db0d8b@kernel.org> <20260424-drm-mode-config-init-v3-10-8b68d9db0d8b@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-v3-10-8b68d9db0d8b@kernel.org> Hi Maxime, Thank you for the patch. On Fri, Apr 24, 2026 at 12:18:50PM +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 planes. > > Signed-off-by: Maxime Ripard > --- > drivers/gpu/drm/drm_atomic_state_helper.c | 25 +++++++++++++++++++++++++ > drivers/gpu/drm/drm_mode_config.c | 21 ++++++++++++++++++++- > include/drm/drm_atomic_state_helper.h | 2 ++ > include/drm/drm_plane.h | 16 ++++++++++++++++ > 4 files changed, 63 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c > index 285efbf29520..50fe4eec41a8 100644 > --- a/drivers/gpu/drm/drm_atomic_state_helper.c > +++ b/drivers/gpu/drm/drm_atomic_state_helper.c > @@ -338,10 +338,35 @@ void drm_atomic_helper_plane_reset(struct drm_plane *plane) > if (plane->state) > __drm_atomic_helper_plane_reset(plane, plane->state); > } > EXPORT_SYMBOL(drm_atomic_helper_plane_reset); > > +/** > + * drm_atomic_helper_plane_create_state - default &drm_plane_funcs.atomic_create_state hook for planes drm_atomic_helper_colorop_create_state() states "Allocates and initializes colorop atomic state", while here you document it as "default hook for planes". Consistency would be good. > + * @plane: plane object > + * > + * Initializes a pristine @drm_plane_state. "Allocate and initialize ..." > + * > + * This is useful for drivers that don't subclass @drm_plane_state. > + * > + * RETURNS: > + * Pointer to new plane state, or ERR_PTR on failure. > + */ > +struct drm_plane_state *drm_atomic_helper_plane_create_state(struct drm_plane *plane) > +{ > + struct drm_plane_state *state; > + > + state = kzalloc_obj(*state); > + if (!state) > + return ERR_PTR(-ENOMEM); > + > + __drm_atomic_helper_plane_state_init(state, plane); > + > + return state; > +} > +EXPORT_SYMBOL(drm_atomic_helper_plane_create_state); > + > /** > * __drm_atomic_helper_plane_duplicate_state - copy atomic plane state > * @plane: plane object > * @state: atomic plane state > * > diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c > index c33382a38191..10b7815cbe48 100644 > --- a/drivers/gpu/drm/drm_mode_config.c > +++ b/drivers/gpu/drm/drm_mode_config.c > @@ -180,10 +180,26 @@ int drm_mode_getresources(struct drm_device *dev, void *data, > drm_connector_list_iter_end(&conn_iter); > > return ret; > } > > +static int drm_mode_config_plane_create_state(struct drm_plane *plane) > +{ > + struct drm_plane_state *plane_state; > + > + if (!plane->funcs->atomic_create_state) > + return 0; > + > + plane_state = plane->funcs->atomic_create_state(plane); > + if (IS_ERR(plane_state)) > + return PTR_ERR(plane_state); > + > + plane->state = plane_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 > @@ -204,13 +220,16 @@ void drm_mode_config_reset(struct drm_device *dev) > struct drm_connector_list_iter conn_iter; > > drm_for_each_colorop(colorop, dev) > drm_colorop_reset(colorop); > > - drm_for_each_plane(plane, dev) > + drm_for_each_plane(plane, dev) { > if (plane->funcs->reset) > plane->funcs->reset(plane); > + else if (plane->funcs->atomic_create_state) > + drm_mode_config_plane_create_state(plane); > + } > > drm_for_each_crtc(crtc, dev) > if (crtc->funcs->reset) > crtc->funcs->reset(crtc); > > diff --git a/include/drm/drm_atomic_state_helper.h b/include/drm/drm_atomic_state_helper.h > index 44e8850aae7f..df371b2eef3e 100644 > --- a/include/drm/drm_atomic_state_helper.h > +++ b/include/drm/drm_atomic_state_helper.h > @@ -53,10 +53,12 @@ void __drm_atomic_helper_crtc_destroy_state(struct drm_crtc_state *state); > void drm_atomic_helper_crtc_destroy_state(struct drm_crtc *crtc, > struct drm_crtc_state *state); > > void __drm_atomic_helper_plane_state_init(struct drm_plane_state *state, > struct drm_plane *plane); > +struct drm_plane_state * > +drm_atomic_helper_plane_create_state(struct drm_plane *plane); > void __drm_atomic_helper_plane_reset(struct drm_plane *plane, > struct drm_plane_state *state); > void drm_atomic_helper_plane_reset(struct drm_plane *plane); > void __drm_atomic_helper_plane_duplicate_state(struct drm_plane *plane, > struct drm_plane_state *state); > diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h > index 703ef4d1bbbc..886e219c4609 100644 > --- a/include/drm/drm_plane.h > +++ b/include/drm/drm_plane.h > @@ -386,10 +386,26 @@ struct drm_plane_funcs { > * 0 on success or a negative error code on failure. > */ > int (*set_property)(struct drm_plane *plane, > struct drm_property *property, uint64_t val); > > + /** > + * @atomic_create_state: > + * > + * Allocates a pristine, initialized, state for the plane object s/Allocates/Allocate/ based on the documentation of other callbacks, and the fact that imperative style is the usual standard in kernel documentation. Reviewed-by: Laurent Pinchart > + * 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, plane state instance or an error pointer > + * on failure. > + */ > + struct drm_plane_state *(*atomic_create_state)(struct drm_plane *plane); > + > /** > * @atomic_duplicate_state: > * > * Duplicate the current atomic state for this plane and return it. > * The core and helpers guarantee that any atomic state duplicated with -- Regards, Laurent Pinchart