From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7E6E9C43215 for ; Tue, 19 Nov 2019 21:52:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5150A2244A for ; Tue, 19 Nov 2019 21:52:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="WRee5CdG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727340AbfKSVwI (ORCPT ); Tue, 19 Nov 2019 16:52:08 -0500 Received: from perceval.ideasonboard.com ([213.167.242.64]:34246 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727007AbfKSVwI (ORCPT ); Tue, 19 Nov 2019 16:52:08 -0500 Received: from pendragon.ideasonboard.com (unknown [122.147.213.64]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id AE238311; Tue, 19 Nov 2019 22:52:03 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1574200324; bh=pKZDqAW7w4txIjgW/O76GhUK4fuak7MVT9x4SR5v3Xw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WRee5CdGqK3CWtUitBFBWteB96nmWUDDo8wYDa0hSo2WvE11HN+ChBhHyGsmn7Yt0 alF01lHubVjJY5KkWVmlmXjIqxYCsCMCIrNL3ndVwIWZCZMGzMHc17v9Jfd+dVroOX I1Opj5bCZ0SsAbz0iYhR/1CmsgNVqp7rpQ2gWG8c= Date: Tue, 19 Nov 2019 23:51:55 +0200 From: Laurent Pinchart To: Fabrizio Castro Cc: Neil Armstrong , David Airlie , Daniel Vetter , Rob Herring , Mark Rutland , Andrzej Hajda , Simon Horman , Geert Uytterhoeven , Magnus Damm , Peter Rosin , "dri-devel@lists.freedesktop.org" , "devicetree@vger.kernel.org" , "linux-renesas-soc@vger.kernel.org" , Chris Paterson , Biju Das , Kieran Bingham , Jacopo Mondi Subject: Re: [PATCH v4 12/13] [HACK] drm/bridge: lvds-codec: Enforce device specific compatible strings Message-ID: <20191119215155.GB17590@pendragon.ideasonboard.com> References: <1573660292-10629-1-git-send-email-fabrizio.castro@bp.renesas.com> <1573660292-10629-13-git-send-email-fabrizio.castro@bp.renesas.com> <20191119001616.GL5171@pendragon.ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi Fabrizio, On Tue, Nov 19, 2019 at 11:17:34AM +0000, Fabrizio Castro wrote: > On 19 November 2019 00:16 Laurent Pinchart wrote: > > On Wed, Nov 13, 2019 at 03:51:31PM +0000, Fabrizio Castro wrote: > > > The lvds-codec driver is a generic stub for transparent LVDS > > > encoders and decoders. > > > It's good practice to list a device specific compatible string > > > > s/good practice/mandatory/ > > Will fix > > > > before the generic fallback (if any) in the DT node for the relevant > > > LVDS encoder/decoder, and it's also required by the dt-bindings. > > > A notable exception to the generic fallback mechanism is the case > > > of "thine,thc63lvdm83d", as documented in: > > > Documentation/devicetree/bindings/display/bridge/thine,thc63lvdm83d.txt > > > This patch enforces the adoption of a device specific compatible > > > string (as fist string in the list), by using markers for the > > > > s/fist/first/ > > Well spotted > > > > > > compatible string we match against and the index of the matching > > > compatible string in the list. > > > > > > Signed-off-by: Fabrizio Castro > > > > > > --- > > > Hi Laurent, > > > > > > I don't think we need to do anything in the driver to address your > > > comment, as we can "enforce" this with the bindings (please see the > > > next patch, as it would help with the "enforcing" of the compatible > > > string for the thine device). > > > I am sending this patch only so that you can see what a possible > > > solution in the driver could look like. > > > > > > v3->v4: > > > * New patch addressing the below comment from Laurent: > > > "I think the lvds-decoder driver should error out at probe time if only > > > one compatible string is listed." > > > --- > > > drivers/gpu/drm/bridge/lvds-codec.c | 55 +++++++++++++++++++++++++++++++++---- > > > 1 file changed, 49 insertions(+), 6 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/bridge/lvds-codec.c b/drivers/gpu/drm/bridge/lvds-codec.c > > > index 784bbd3..145c25d 100644 > > > --- a/drivers/gpu/drm/bridge/lvds-codec.c > > > +++ b/drivers/gpu/drm/bridge/lvds-codec.c > > > @@ -14,11 +14,16 @@ > > > #include > > > #include > > > > > > +struct lvds_codec_data { > > > + u32 connector_type; > > > + bool device_specific; > > > +}; > > > + > > > struct lvds_codec { > > > struct drm_bridge bridge; > > > struct drm_bridge *panel_bridge; > > > struct gpio_desc *powerdown_gpio; > > > - u32 connector_type; > > > + const struct lvds_codec_data *data; > > > }; > > > > > > static int lvds_codec_attach(struct drm_bridge *bridge) > > > @@ -65,7 +70,30 @@ static int lvds_codec_probe(struct platform_device *pdev) > > > if (!lvds_codec) > > > return -ENOMEM; > > > > > > - lvds_codec->connector_type = (u32)of_device_get_match_data(&pdev->dev); > > > + lvds_codec->data = of_device_get_match_data(&pdev->dev); > > > + if (!lvds_codec->data) > > > + return -EINVAL; > > > + > > > + /* > > > + * If we haven't matched a device specific compatible string, we need > > > + * to work out if the generic compatible string we matched against was > > > + * listed first in the compatible property. > > > + */ > > > > Can't we do this unconditionally, and thus drop the lvds_codec_data > > structure ? > > I don't think so, and the reason for this is that we have a corner case for > thine,thc63lvdm83d. Here is what's allowed (according to the documentation) > from what's supported upstream (+ this series): > "ti,ds90c185", "lvds-encoder" > "ti,ds90c187", "lvds-encoder" > "ti,sn75lvds83", "lvds-encoder" > "ti,ds90cf384a", "lvds-decoder" > "thine,thc63lvdm83d" > > As you can see from the examples above, in most cases it's enough to say it's > all good when we match a compatible string with index > 0, but for the thine > device you _have_ to match the string with index 0 as that's what's currently > documented (please see thine,thc63lvdm83d.txt) and that's what's supported > by device trees already (please see arch/arm/boot/dts/r8a7779-marzen.dts). How about the following logic ? if (match_index("lvds-encoder") == 0 || match_index("lvds-decoder") == 0) return -EINVAL; ? > This patch "classifies" compatible strings, and it considers a good match > device specific compatible strings, or generic compatible strings as long > as they are not listed first. > > These days you can leverage the yaml files to validate the device trees, > therefore we should be focusing on writing yaml files in such a way we only > pass the checks we mean to, and by checks I mean: > make dtbs_check > > or more specifically, for this series: > make dtbs_check DT_SCHEMA_FILES=Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml > > and that's of course on top of make dt_binding_check. Sure, but that doesn't prevent anyone ignoring the validation. > It's a very common requirement to have a part number specific compatible > string first followed by a generic (fallback) compatible string in the device trees, > most drivers for Renesas SoCs have similar requirements. > > If we start doing this here, we'll end up doing it elsewhere as well, and I really > think we shouldn't, but others may see things differently, so I'll wait for others > (and yourself with further comments) to jump in before doing any more work > on this patch. I agree with this argument, it would set a precedent, and is probably not worth duplicating similar code in all drivers. I wonder if this is something we could handle with core helpers, but maybe it's overkill. > > > + if (!lvds_codec->data->device_specific) { > > > + const struct of_device_id *match; > > > + int compatible_index; > > > + > > > + match = of_match_node(dev->driver->of_match_table, > > > + dev->of_node); > > > + compatible_index = of_property_match_string(dev->of_node, > > > + "compatible", > > > + match->compatible); > > > + if (compatible_index == 0) { > > > + dev_err(dev, "Device specific compatible needed\n"); > > > + return -EINVAL; > > > + } > > > + } > > > + > > > lvds_codec->powerdown_gpio = devm_gpiod_get_optional(dev, "powerdown", > > > GPIOD_OUT_HIGH); > > > if (IS_ERR(lvds_codec->powerdown_gpio)) { > > > @@ -92,7 +120,7 @@ static int lvds_codec_probe(struct platform_device *pdev) > > > > > > lvds_codec->panel_bridge = > > > devm_drm_panel_bridge_add_typed(dev, panel, > > > - lvds_codec->connector_type); > > > + lvds_codec->data->connector_type); > > > if (IS_ERR(lvds_codec->panel_bridge)) > > > return PTR_ERR(lvds_codec->panel_bridge); > > > > > > @@ -119,18 +147,33 @@ static int lvds_codec_remove(struct platform_device *pdev) > > > return 0; > > > } > > > > > > +static const struct lvds_codec_data lvds_codec_decoder_data = { > > > + .connector_type = DRM_MODE_CONNECTOR_DPI, > > > + .device_specific = false, > > > +}; > > > + > > > +static const struct lvds_codec_data lvds_codec_encoder_data = { > > > + .connector_type = DRM_MODE_CONNECTOR_LVDS, > > > + .device_specific = false, > > > +}; > > > + > > > +static const struct lvds_codec_data lvds_codec_thc63lvdm83d_data = { > > > + .connector_type = DRM_MODE_CONNECTOR_LVDS, > > > + .device_specific = true, > > > +}; > > > + > > > static const struct of_device_id lvds_codec_match[] = { > > > { > > > .compatible = "lvds-decoder", > > > - .data = (void *)DRM_MODE_CONNECTOR_DPI, > > > + .data = &lvds_codec_decoder_data, > > > }, > > > { > > > .compatible = "lvds-encoder", > > > - .data = (void *)DRM_MODE_CONNECTOR_LVDS, > > > + .data = &lvds_codec_encoder_data, > > > }, > > > { > > > .compatible = "thine,thc63lvdm83d", > > > - .data = (void *)DRM_MODE_CONNECTOR_LVDS, > > > + .data = &lvds_codec_thc63lvdm83d_data, > > > }, > > > {}, > > > }; -- Regards, Laurent Pinchart