linux-kernel - Re: [PATCH 22/29] drm/tidss: crtc: Cleanup reset implementation

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Message-ID: <4dfb851d-cd13-47cf-9965-774396bb0071@suse.de>
Date: Tue, 2 Sep 2025 15:54:16 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Maxime Ripard <mripard@...nel.org>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Jyri Sarha <jyri.sarha@....fi>,
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: Devarsh Thakkar <devarsht@...com>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 22/29] drm/tidss: crtc: Cleanup reset implementation



Am 02.09.25 um 10:32 schrieb Maxime Ripard:
> The tidss_crtc_reset() function will (rightfully) destroy any
> pre-existing state.
>
> However, the tidss CRTC driver has its own CRTC state structure that
> subclasses drm_crtc_state, and yet will destroy the previous state
> by calling __drm_atomic_helper_crtc_destroy_state() and kfree() on its
> drm_crtc_state pointer.
>
> It works only because the drm_crtc_state is the first field in the
> structure, and thus its offset is 0. It's incredibly fragile however, so
> let's call our destroy implementation in such a case to deal with it
> properly.
>
> Signed-off-by: Maxime Ripard <mripard@...nel.org>

Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>

> ---
>   drivers/gpu/drm/tidss/tidss_crtc.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/tidss/tidss_crtc.c b/drivers/gpu/drm/tidss/tidss_crtc.c
> index eb431a238b11d22349d61f0e17f05994f50d5f2f..8fcc6a2f94770ae825eeb2a3b09856a2bf2d6a1e 100644
> --- a/drivers/gpu/drm/tidss/tidss_crtc.c
> +++ b/drivers/gpu/drm/tidss/tidss_crtc.c
> @@ -355,13 +355,11 @@ static void tidss_crtc_destroy_state(struct drm_crtc *crtc,
>   static void tidss_crtc_reset(struct drm_crtc *crtc)
>   {
>   	struct tidss_crtc_state *tstate;
>   
>   	if (crtc->state)
> -		__drm_atomic_helper_crtc_destroy_state(crtc->state);
> -
> -	kfree(crtc->state);
> +		tidss_crtc_destroy_state(crtc, crtc->state);
>   
>   	tstate = kzalloc(sizeof(*tstate), GFP_KERNEL);
>   	if (!tstate) {
>   		crtc->state = NULL;
>   		return;
>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)