From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.10]) (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 7FAF63C9ED6 for ; Wed, 1 Apr 2026 12:56:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775048177; cv=none; b=nyfyekGhWDtVmQyR9Im6uaFcfkz/l6wdtUMpv1th5p0YkSLG8KtQW8KdfR0KNpkaCxQ50tZ5ynEwikkBQgczg+ItNpKo+WwZzDGb+Kdo0FC8H0u/oB8BH5jzhlT9u6XJlgqrT0aPzoGU2b1eqB9kiXM/p/U8K0OojLx3+/fVHs8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775048177; c=relaxed/simple; bh=5zPr3Fy9/dtEUiFn8VgaF3h/MqP5no3JhMn4H+5M3hU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HJe1k77W3mH83V+rQ53AQe/xOZEdoWm5TkKbiYIul6QoHkihq3TLGYby8nF9W2qprR2fdQ9yaFIxQnSRSME3RCdap+4WmsnpdJQQHpiyWtcD631fIYvp/CPPK0x9fjC5pO4YbGI2Xf2Rk+GzIixDeu2sXAzGC8f+nniTxIhcagY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Vn+nwUSX; arc=none smtp.client-ip=192.198.163.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Vn+nwUSX" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1775048175; x=1806584175; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=5zPr3Fy9/dtEUiFn8VgaF3h/MqP5no3JhMn4H+5M3hU=; b=Vn+nwUSXKvFcODGNfMjPOtQQazRgON6d3KaHRDdLnXqzZLXMUPs8OmoI dGQcaJoEF26dqIO0S/SbmPYl3fD8t+I/2pPbTqmxqmSWh0seijj+QJw1Z CdGlZ9Lst0lkoWn9ykyldQjIwIrXwpuDUY3+W7K3809t4FqJ/rZwqYhS4 Ya0RJFFsybe31pMaeFa9xz9s/g6bgtE6VtPu1twB4j8/a2++Cjgu/8JRa ONm7QEsSsqdqiXGw0eu0ORIYaySbUcm0Mcaa1s+Qj4jnqyQH+SQyYpnqK NVlyuCtiB7cjhIyYVLb/ee6dyX531Aj4BBXiecmAMjYZcl5L+uSLQeDHf A==; X-CSE-ConnectionGUID: hT8mLeQVRG2RADrMi0qalg== X-CSE-MsgGUID: Uwhry7FURJC+rmFzrwToHA== X-IronPort-AV: E=McAfee;i="6800,10657,11745"; a="87472603" X-IronPort-AV: E=Sophos;i="6.23,153,1770624000"; d="scan'208";a="87472603" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by fmvoesa104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Apr 2026 05:56:14 -0700 X-CSE-ConnectionGUID: E2XgVs58T3igKGA2NhJL8w== X-CSE-MsgGUID: G4/O/++ERsq34MnbY6ttEQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,153,1770624000"; d="scan'208";a="221813823" Received: from pgcooper-mobl3.ger.corp.intel.com (HELO localhost) ([10.245.244.199]) by fmviesa006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Apr 2026 05:56:10 -0700 Date: Wed, 1 Apr 2026 15:56:06 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Daniel Stone Cc: Xaver Hugl , Nicolas Frattaroli , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Harry Wentland , Leo Li , Rodrigo Siqueira , Alex Deucher , Christian =?iso-8859-1?Q?K=F6nig?= , Daniel Stone , Dmitry Baryshkov , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, kernel@collabora.com, Derek Foreman , Marius Vlad , wayland-devel@lists.freedesktop.org Subject: Re: [PATCH v5 0/3] Add "link bpc" DRM property Message-ID: References: <20260319-link-bpc-v5-0-5306cd04a708@collabora.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Patchwork-Hint: comment Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs Bertel Jungin Aukio 5, 02600 Espoo, Finland On Wed, Apr 01, 2026 at 01:25:31PM +0100, Daniel Stone wrote: > On Wed, 1 Apr 2026 at 13:11, Ville Syrjälä > wrote: > > I think the idea of some kind of feedback properties in the atomic > > commit has come up before, but no one has ever tried to implement them. > > Yeah, if you're looking for context on these, the last place I > remember it coming up was wanting to know which other objects would > potentially be dragged into a commit. For example, on ye olde (?) > Intel platforms, if programming a different mode is actually > stop-the-world where all other CRTCs get affected by a CDCLK change, > being able to know that those other CRTCs would be affected before it > happens, rather than random -EBUSY after the fact. For the success cases I think it should be pretty straightforward to just walk the props in the commit again after the atomic check and write back all the feedback values from the computed state. I think adding this for error cases would be much harder. We'd have to somehow make sure the value(s) we write back to userspace are at least somewhat valid even though the state check may have failed half way through. Although that specific -EBUSY you mention I think is checked after the actual atomic check, so it would work there. Assuming we'd have a place for eg. the affected crtcs bitmask in the ioctl structure... And speaking of which, if you'll permit me to go off on another tangent, I have occasionally pondered introducing per-device properties. We could introduce a new object type for the whole device, and add a new enumeration thing to find it. Then per-device properties could be added to atomic commits exactly like any other properties. My original idea was to use this for some kind of device wide "power vs. performance" knob, but it could also be used for this affected crtcs bitmask feedback. -- Ville Syrjälä Intel