From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751956AbcFWInm (ORCPT ); Thu, 23 Jun 2016 04:43:42 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:33670 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751933AbcFWIni (ORCPT ); Thu, 23 Jun 2016 04:43:38 -0400 Date: Thu, 23 Jun 2016 10:43:35 +0200 From: Thierry Reding To: Tomeu Vizoso Cc: Jani Nikula , Daniel Vetter , Daniel Vetter , Emil Velikov , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" Subject: Re: [PATCH v1 2/3] drm: Add API for capturing frame CRCs Message-ID: <20160623084335.GC8136@ulmo.ba.sec> References: <1466507202-23222-1-git-send-email-tomeu.vizoso@collabora.com> <1466507202-23222-3-git-send-email-tomeu.vizoso@collabora.com> <20160621150758.GB21079@ulmo.ba.sec> <20160622133216.GL26943@ulmo.ba.sec> <20160622143144.GN26943@ulmo.ba.sec> <8760t0jox2.fsf@intel.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ZwgA9U+XZDXt4+m+" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --ZwgA9U+XZDXt4+m+ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jun 23, 2016 at 10:24:46AM +0200, Tomeu Vizoso wrote: > On 23 June 2016 at 10:21, Jani Nikula wrote: > > On Wed, 22 Jun 2016, Daniel Vetter wrote: > >> On Wed, Jun 22, 2016 at 4:31 PM, Thierry Reding > >> wrote: > >>> Perhaps another way to avoid that would be to put the two files into a > >>> separate directory, as in: > >>> > >>> /sys/kernel/debug/dri//crtc-/crc/ > >>> +-- control > >>> +-- data > >>> > >>> That's slightly on the deeply nested side, but on the other hand it > >>> nicely uses the filesystem for namespacing, which is what filesystems > >>> are really good at. > >> > >> crtc-/crc/(control|data) sounds great. > > > > Side note, we should eventually do the same for sink CRCs, but I guess > > under the connectors. i915 currently has a special cased version for eDP > > (named "i915_sink_crc_eDP1"...), reading the data from DPCD. >=20 > Was hoping we could just add one more source to this interface to expose = those. I don't think that would be easy to achieve. You'd have to determine that a sink source is connected to the CRTC and then ajdust the list of possible sources dynamically. For connectors we already have separate directories in debugfs and a sink can easily be found from the connector it is attached to. It's also possible, though I don't know of any that do so currently, that eventually sinks will support several types (i.e. "sources") of CRC, which will further complicate to represent this in the CRTC's list of CRC sources. And it may also be useful to have both CRCs at the same time. The eDP specification for example defines a very specific polynomial that is used to compute the CRC, whereas not all display hardware uses a CRC algorithm that's documented. Finally, the data that will be checksummed by the CRTC isn't necessarily the same as that arriving at the sink. Thierry --ZwgA9U+XZDXt4+m+ Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAABCAAGBQJXa6E0AAoJEN0jrNd/PrOhrUMQAKWx1vyKDMq8adLY+oJLNiAG CqhstPr7y4AWT39oAENRHaMw+UM8tXnelrXacsmIj2Cr9O1Bv8QncMZXN/hXFuCZ m2dL6wnYcHIP8E/wn62gNe3Yq3wRVMl8BQv0qvq6YbnIzVrQtVuu21cg0D/wXTCR 26ouCQW+zm/yVM//MeB9/wHP5hcl3xuoy7zAG4dFT/eqjRLyDNgaOpzKr2A7+KYt QGgpVYxkkK/fzEb/tTrRgxv9iY3B8p8o4rK0aoOsfYBeqiMLS8Of31sVIvkFUhWe ZG1Gr1mXGu3cfuDLP0kWUeMtUwt86UACCsmbYbjM1KhZnDtXNoQyrcA/ex0v2vSO /ztVtl8ZFzw387Px7XTz6F9xfi2/fHZqjCYTWx+QEmZIZvxyBo9997BuP+yhPeIC +0ECIV7bGx8mBy6UWFHr08mHodOBCfG7p8yOyxev8bJoLAo0rKrnooTm6HQsCbZx gTIx3PcLbAxtGEywaNVHrU+loyM+qcKqmFUO/mvFtfVwxWAk9x95xQawywo1BfvV +9K0xBZYIt+qzJVgB9arUhgZ5QXM1TLts9tbf8CTBsCXFSAjVw//F/1bKH8dnAhx 0zqxAlv6dQU8u76gr0eAv2s3JEO4cknPd+nsfKvRDmpKZpdH7VjCOnosJH8pwlPa HKuItrJJd6qtwxDwc/5x =x1hM -----END PGP SIGNATURE----- --ZwgA9U+XZDXt4+m+--