From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender4-op-o11.zoho.com (sender4-op-o11.zoho.com [136.143.188.11]) (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 27A29368277 for ; Thu, 30 Jul 2026 18:55:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.11 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785437726; cv=pass; b=bryJBuljyUSaO9qX+lqundPKnd1pFCw6fBfpZ03Nfnv94I0IM78BMlA7ORAgYlknWJ+1Cs2mA9M7LhUIlrsR93wdU+OvIbxcCkRz2eDZgWkZy+meINg8HVNdTMmjAjirJ9oV8YCritlAQiSAr4AwV20nL6Crls9fHszgNcXhzHs= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785437726; c=relaxed/simple; bh=oZh0BSe7s+4S6EJJNjh0tNGV4zCJfXWjT7E4O4uSEqE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=W81HIPalB54Qi+3wYKs5//750R6o26z7Kc/jY7XlQD96puAxpYUz5h18KHAfNt/oplG/dqTUNKN/rlZBdf8J8xzFpov127mSJsszAbPUEaZBhnZaog3rMm5xa5J2qagfFtrRqKXp3gY3eL3ghZ37pl7HfXSDUZcngnAklcmaM1s= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (1024-bit key) header.d=collabora.com header.i=leandro.ribeiro@collabora.com header.b=HLl/j4xV; arc=pass smtp.client-ip=136.143.188.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=collabora.com header.i=leandro.ribeiro@collabora.com header.b="HLl/j4xV" ARC-Seal: i=1; a=rsa-sha256; t=1785437703; cv=none; d=zohomail.com; s=zohoarc; b=KF8xdYFkiAHfsZzZwCtc6DDFV1VVV320azulRXqWAZdzoZ33S883WCrUO364HDCNScjElUtMF7ZJquQgBuTJxG6xKtHppiCznOvPxnO+pB5p9pdq9J+eixLTSCdOzDwK5hdpZN2PpzD+i7sRB3rIM+BBTjJvabWFt5RJ9+u4ML0= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1785437703; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:Subject:Subject:To:To:Message-Id:Reply-To; bh=9AIxGw1TLp+p2tcxS7/F14XLcUmuxOVmyqIJY65QchY=; b=O1iPcOOrPQXk5cdFiV1wKo706fUyhY9reIdeoA3lFkOgct2DURrlUp22cyarLF/a7Mjl0FbA3kOcDtXeQDAw6ezJDIVwdrzN411WJTDuadVAjkmoLo3gjfg9nl8pkdImb5Z6gIGbE6zl7io5dkWXyEo+WqoSL3Vk049XZBKUrGY= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=leandro.ribeiro@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1785437703; s=zohomail; d=collabora.com; i=leandro.ribeiro@collabora.com; h=Message-ID:Date:Date:MIME-Version:Subject:Subject:To:To:Cc:Cc:From:From:In-Reply-To:Content-Type:Content-Transfer-Encoding:Message-Id:Reply-To; bh=9AIxGw1TLp+p2tcxS7/F14XLcUmuxOVmyqIJY65QchY=; b=HLl/j4xVw/vZVmiOdCOGpTkFDGK5kwMUuoUSEs3OkbE9kUth8Ys3F5JUqXUfkW+L aXKHjwAAD9LBGIwvUYA4drvU0CNYkuWrZXZoZJYVbszJW03vBFQ/AQ2gUi/aDf1lsR1 Ny7IJuZzGEG3FMdLR1wRLL/y9aQt//O1U0EoQybA= Received: by mx.zohomail.com with SMTPS id 1785437700926956.5335535558954; Thu, 30 Jul 2026 11:55:00 -0700 (PDT) Message-ID: <5d8ff369-8afa-4fcf-906b-ab685fa04e42@collabora.com> Date: Thu, 30 Jul 2026 15:54:55 -0300 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 1/1] drm: use drm_warn() in validate_blend_mode_for_alpha_formats() To: Tetsuo Handa , dri-devel@lists.freedesktop.org Cc: airlied@gmail.com, broonie@kernel.org, daniels@collabora.com, jani.nikula@linux.intel.com, maarten.lankhorst@linux.intel.com, miguel.ojeda.sandonis@gmail.com, mripard@kernel.org, pekka.paalanen@collabora.com, simona@ffwll.ch, tytso@mit.edu, tzimmermann@suse.de, ville.syrjala@linux.intel.com, linux-kernel@vger.kernel.org References: <20260729214505.185776-1-leandro.ribeiro@collabora.com> <20260729214505.185776-2-leandro.ribeiro@collabora.com> Content-Language: en-US From: Leandro Ribeiro In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ZohoMailClient: External On 7/29/26 7:13 PM, Tetsuo Handa wrote: > On 2026/07/30 6:45, Leandro Ribeiro wrote: >> Commit 860e748bddcc ("drm: ensure blend mode supported if pixel format >> with alpha exposed") introduced a WARN() to let driver developers know >> that a previously valid behavior should now be changed. >> >> But WARN() should not be used for that, as it's a kernel warning report >> mechanism for conditions that are not expected to happen. It also >> produces a stack trace. Instead, a simple warning-level log message >> should have been used, as drivers were expected to trigger the >> condition. >> >> This is causing problems for fuzzers, as they may stop when encountering >> a "BUG:" or "WARNING:" in the logs. >> >> Replace WARN() with drm_warn() in this function, avoiding these issues. > > Thank you. But could something like > > pr_warn("[PLANE:%d:%s] pixel format with alpha exposed but blend mode not setup. Please fix.", plane->base.id, plane->name); > dump_stack(); > > be less prone to get oversighted (because of printing about 10+ lines)? > I see the point about making the message harder to overlook, but honestly I feel like the stack trace would be overkill here. The error message is more important than the stack trace itself in this case, and I think the warning should be enough to draw attention to the issue. -- Leandro Ribeiro