From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0FDC217A309 for ; Wed, 1 Oct 2025 06:45:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759301121; cv=none; b=X0M4MnscRbz3RiPWxq9bAb4iAbMO3EXhjOnWK/lMAs9Z3ln3StmuZU7qL4H1YaQJud/YUdtznz18USgVHXMNrDc7kU1nSy5MvKj8Pxp3R6sgoB/INahvmzyzXZx3ESVY8Pj5zablbjOGoBk0YZVpAKcQkDKFs+Cl2IF/8i4JjSs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759301121; c=relaxed/simple; bh=VxUm68KnN3zve6Y7r2MoaVHxMdaOwTiutr/1eLOAZ6c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=be3cs+2puTd1PsD/7QJkkdH6rDpQKfgM4Dj76u+up7qSgW+CQQjoxvGiD8pUdJDMeVqP8rinFf2eEWEvlYI15hRMB53b3ePwsqYK56sEzSHP9N3I6z20t54s7L4SCQbPH+qWWMmTFSuN1ObTaQcjBznC6Bc/o/y81Hv56Uk+gLc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de; spf=pass smtp.mailfrom=suse.de; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b=aUZkunx5; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b=T6/tIUcI; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b=bTFuO2ap; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b=KP33YJWM; arc=none smtp.client-ip=195.135.223.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="aUZkunx5"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="T6/tIUcI"; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="bTFuO2ap"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="KP33YJWM" Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id D47A533777; Wed, 1 Oct 2025 06:45:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1759301111; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=3PUW0GlmkITYxestkhaDP2QY5zJfTZgpkkxNAnVT6jw=; b=aUZkunx5mDUXFOlN1mJVKwdPQ+wh0GesC1xVPPwI1IJQ9bK5oBN7Q4ry0g86ln4GnxL+7f GzVAR1JeEj1beIucY9HD2M0E3F1vpIgxXQedLvbQ3+be7kHTAsvhreTtPyPk5NNjxnJORN rXs63xs2cJeWZoUYJgXzMdPgHj7GPU4= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1759301111; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=3PUW0GlmkITYxestkhaDP2QY5zJfTZgpkkxNAnVT6jw=; b=T6/tIUcIYtTeVx41yEYdrJgLRBcRQ8EIIPdUZer1jiPJCn4XWMIVf0RVmnADq3HHB/he80 hofD6XCfuOsdKjBw== Authentication-Results: smtp-out1.suse.de; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=bTFuO2ap; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=KP33YJWM DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1759301110; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=3PUW0GlmkITYxestkhaDP2QY5zJfTZgpkkxNAnVT6jw=; b=bTFuO2apah1VMvPzz0pLOMyctDvBe/cC7423V6MekBaObevQjDWX4ufFHJE8tlzqnRuD1c a6+a2/qO3fwxgnvrnTK1GMa9Mm4u9XF+KQ8Le/X16vcq9a281Id5AJb4g3ZnJRQLUwL9iB M9p7BKyw01WAKrnX26/7zV/1WMBG3a4= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1759301110; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=3PUW0GlmkITYxestkhaDP2QY5zJfTZgpkkxNAnVT6jw=; b=KP33YJWMHNcXzO7iCGx9srRd13SA2JRXlkhzWg9aoR5Dymsj71sKje1AnaW1kij7qobscH hhaF2nd8LFmnMcBw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 5C66313A3F; Wed, 1 Oct 2025 06:45:10 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id NbbPFPbN3Gh5EAAAD6G6ig (envelope-from ); Wed, 01 Oct 2025 06:45:10 +0000 Message-ID: Date: Wed, 1 Oct 2025 08:45:09 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 05/29] drm/atomic_state_helper: Fix bridge state initialization To: Maxime Ripard Cc: Maarten Lankhorst , David Airlie , Simona Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Jyri Sarha , Tomi Valkeinen , Devarsh Thakkar , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20250902-drm-state-readout-v1-0-14ad5315da3f@kernel.org> <20250902-drm-state-readout-v1-5-14ad5315da3f@kernel.org> <9f17dfd9-a4d4-41e9-b988-bd8ca858e5e7@suse.de> <20250915-heavenly-athletic-lionfish-aa7b8b@penduick> <9520bcb5-df81-452c-902a-0c4c61156716@suse.de> <20250923-dynamic-bumblebee-of-luck-d31a19@penduick> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; keydata= xsBNBFs50uABCADEHPidWt974CaxBVbrIBwqcq/WURinJ3+2WlIrKWspiP83vfZKaXhFYsdg XH47fDVbPPj+d6tQrw5lPQCyqjwrCPYnq3WlIBnGPJ4/jreTL6V+qfKRDlGLWFjZcsrPJGE0 BeB5BbqP5erN1qylK9i3gPoQjXGhpBpQYwRrEyQyjuvk+Ev0K1Jc5tVDeJAuau3TGNgah4Yc hdHm3bkPjz9EErV85RwvImQ1dptvx6s7xzwXTgGAsaYZsL8WCwDaTuqFa1d1jjlaxg6+tZsB 9GluwvIhSezPgnEmimZDkGnZRRSFiGP8yjqTjjWuf0bSj5rUnTGiyLyRZRNGcXmu6hjlABEB AAHNJ1Rob21hcyBaaW1tZXJtYW5uIDx0emltbWVybWFubkBzdXNlLmRlPsLAjgQTAQgAOAIb AwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftODH AAoJEGgNwR1TC3ojx1wH/0hKGWugiqDgLNXLRD/4TfHBEKmxIrmfu9Z5t7vwUKfwhFL6hqvo lXPJJKQpQ2z8+X2vZm/slsLn7J1yjrOsoJhKABDi+3QWWSGkaGwRJAdPVVyJMfJRNNNIKwVb U6B1BkX2XDKDGffF4TxlOpSQzdtNI/9gleOoUA8+jy8knnDYzjBNOZqLG2FuTdicBXblz0Mf vg41gd9kCwYXDnD91rJU8tzylXv03E75NCaTxTM+FBXPmsAVYQ4GYhhgFt8S2UWMoaaABLDe 7l5FdnLdDEcbmd8uLU2CaG4W2cLrUaI4jz2XbkcPQkqTQ3EB67hYkjiEE6Zy3ggOitiQGcqp j//OwE0EWznS4AEIAMYmP4M/V+T5RY5at/g7rUdNsLhWv1APYrh9RQefODYHrNRHUE9eosYb T6XMryR9hT8XlGOYRwKWwiQBoWSDiTMo/Xi29jUnn4BXfI2px2DTXwc22LKtLAgTRjP+qbU6 3Y0xnQN29UGDbYgyyK51DW3H0If2a3JNsheAAK+Xc9baj0LGIc8T9uiEWHBnCH+RdhgATnWW GKdDegUR5BkDfDg5O/FISymJBHx2Dyoklv5g4BzkgqTqwmaYzsl8UxZKvbaxq0zbehDda8lv hFXodNFMAgTLJlLuDYOGLK2AwbrS3Sp0AEbkpdJBb44qVlGm5bApZouHeJ/+n+7r12+lqdsA EQEAAcLAdgQYAQgAIAIbDBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftOH6AAoJEGgNwR1T C3ojVSkIALpAPkIJPQoURPb1VWjh34l0HlglmYHvZszJWTXYwavHR8+k6Baa6H7ufXNQtThR yIxJrQLW6rV5lm7TjhffEhxVCn37+cg0zZ3j7zIsSS0rx/aMwi6VhFJA5hfn3T0TtrijKP4A SAQO9xD1Zk9/61JWk8OysuIh7MXkl0fxbRKWE93XeQBhIJHQfnc+YBLprdnxR446Sh8Wn/2D Ya8cavuWf2zrB6cZurs048xe0UbSW5AOSo4V9M0jzYI4nZqTmPxYyXbm30Kvmz0rYVRaitYJ 4kyYYMhuULvrJDMjZRvaNe52tkKAvMevcGdt38H4KSVXAylqyQOW5zvPc4/sq9c= In-Reply-To: <20250923-dynamic-bumblebee-of-luck-d31a19@penduick> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Level: X-Spam-Flag: NO X-Rspamd-Queue-Id: D47A533777 X-Rspamd-Action: no action X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[15]; FUZZY_RATELIMITED(0.00)[rspamd.com]; MIME_TRACE(0.00)[0:+]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; FREEMAIL_CC(0.00)[linux.intel.com,gmail.com,ffwll.ch,intel.com,linaro.org,kernel.org,ideasonboard.com,kwiboo.se,iki.fi,ti.com,lists.freedesktop.org,vger.kernel.org]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from,2a07:de40:b281:106:10:150:64:167:received]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; TAGGED_RCPT(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.de:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:mid] X-Spam-Score: -3.01 Hi Am 23.09.25 um 11:33 schrieb Maxime Ripard: > On Mon, Sep 15, 2025 at 03:12:11PM +0200, Thomas Zimmermann wrote: >> Hi >> >> Am 15.09.25 um 13:27 schrieb Maxime Ripard: >>> On Tue, Sep 02, 2025 at 03:18:17PM +0200, Thomas Zimmermann wrote: >>>> Hi >>>> >>>> Am 02.09.25 um 10:32 schrieb Maxime Ripard: >>>>> Bridges implement their state using a drm_private_obj and an >>>>> hand-crafted reset implementation. >>>>> >>>>> Since drm_private_obj doesn't have a set of reset helper like the other >>>>> states, __drm_atomic_helper_bridge_reset() was initializing both the >>>>> drm_private_state and the drm_bridge_state structures. >>>>> >>>>> This initialization however was missing the drm_private_state.obj >>>>> pointer to the drm_private_obj the state was allocated for, creating a >>>>> NULL pointer dereference when trying to access it. >>>>> >>>>> Fixes: 751465913f04 ("drm/bridge: Add a drm_bridge_state object") >>>>> Signed-off-by: Maxime Ripard >>>>> --- >>>>> drivers/gpu/drm/drm_atomic_state_helper.c | 8 ++++++++ >>>>> 1 file changed, 8 insertions(+) >>>>> >>>>> diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c >>>>> index 7142e163e618ea0d7d9d828e1bd9ff2a6ec0dfeb..b962c342b16aabf4e3bea52a914e5deb1c2080ce 100644 >>>>> --- a/drivers/gpu/drm/drm_atomic_state_helper.c >>>>> +++ b/drivers/gpu/drm/drm_atomic_state_helper.c >>>>> @@ -707,10 +707,17 @@ void drm_atomic_helper_connector_destroy_state(struct drm_connector *connector, >>>>> __drm_atomic_helper_connector_destroy_state(state); >>>>> kfree(state); >>>>> } >>>>> EXPORT_SYMBOL(drm_atomic_helper_connector_destroy_state); >>>>> +static void __drm_atomic_helper_private_obj_reset(struct drm_private_obj *obj, >>>>> + struct drm_private_state *state) >>>>> +{ >>>>> + memset(state, 0, sizeof(*state)); >>>> This argument is guaranteed to be zero'd, I think. No need for a memset. >>>> >>>>> + state->obj = obj; >>>>> +} >>>>> + >>>>> /** >>>>> * __drm_atomic_helper_private_obj_duplicate_state - copy atomic private state >>>>> * @obj: CRTC object >>>>> * @state: new private object state >>>>> * >>>>> @@ -796,10 +803,11 @@ EXPORT_SYMBOL(drm_atomic_helper_bridge_destroy_state); >>>>> */ >>>>> void __drm_atomic_helper_bridge_reset(struct drm_bridge *bridge, >>>>> struct drm_bridge_state *state) >>>>> { >>>>> memset(state, 0, sizeof(*state)); >>>> Another unnecessary memset? >>> I guess the two can be seen as redundant, but I'd argue the one in >>> __drm_atomic_helper_private_obj_reset should still be there. >>> >>> What guarantees that the pointer points to a zero'd structure? >> We only call this helper after allocation AFAICT. And the DRM APIs already >> assume that allocation clears to zero. > Really? Do we have that documented anywhere? I don't think it's documented anywhere, but that's what Sima told me when I tried to write similar code. The rule was to alloc zero'd memory and than have init functions only set what is necessary, but keep others to zero. I think it can be seen in certain places, where drivers set a variety of flags or fields before calling an init helper. Creating a GEM object from shmem is an example. [1] [1] https://elixir.bootlin.com/linux/v6.17/source/drivers/gpu/drm/drm_gem_shmem_helper.c#L52 Best regards Thomas > > And even then, there's nothing that requires that helper to be called > straight-away after allocation. > > More importantly, do we really care about skipping them? Like, all the > other reset helpers are doing it, it's cheap, safe, why should we remove > it? > > Maxime -- -- 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)