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 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D07E7C35268 for ; Mon, 24 Jan 2022 19:37:18 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id F396310E1A8; Mon, 24 Jan 2022 19:37:17 +0000 (UTC) Received: from mail-oi1-x22f.google.com (mail-oi1-x22f.google.com [IPv6:2607:f8b0:4864:20::22f]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0890210E1A8 for ; Mon, 24 Jan 2022 19:37:17 +0000 (UTC) Received: by mail-oi1-x22f.google.com with SMTP id y23so8863377oia.13 for ; Mon, 24 Jan 2022 11:37:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6T+a8Bx06xvDutb5+VHfkoYO4ESKNGds/DLEsaoyVx8=; b=FMSnFxr7XrvMSHM8YrAM6NA5d3ET8kIpzVnWIzWt1EKy7/wkEHXze29Yi49fGJq+Y5 GnxGPakbkFU5mIiNUV80zkvcs5Lq3FDyau5p4lc5ZHUMincF4tlOGxC64RcVK/YGhUhh TA7kmVkXemc68K3B6H4WUIdjUnrcj0Z5AQRok= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=6T+a8Bx06xvDutb5+VHfkoYO4ESKNGds/DLEsaoyVx8=; b=3dTg2McLSy6lmMr3s81lrOfPHqZNxqXmPXH3e1zoDAEAriY1FS7QGD+EA8PrCpmie0 yWX3pRfR2uJhhds11YwF90Vqt14YAD+CokdVY6GgXEVHeYHgugXS7NGFRFt43g9A+fOz i3VEMs5Vw/OKScOCzEIhf/nEhq3NwZFhHXtDIfCoEhlHIWqAhjnM3cLtqJYjBG3bES4S XWExfWsiymt6jjzhXn7cFGL7AMSWlP8Y6BorFj8qWM3cugpVORJbaIRG1iERkdiSvcKV WEAf/yNrBBIa3zliBiGzxtFREFYrC6LZvj6U0uZ5R/78NxBKibwtFPBypmEOyFy3QY5Q r27Q== X-Gm-Message-State: AOAM531MVAIUrE+SrdqpVRvIjT+SEldyvCm8j4a5DhRCWVrlV/ex2G1r 7eMIlep1jSJO6hLTD8EF/CbqZRbXsLxvD+OZV08vP97CWfY= X-Google-Smtp-Source: ABdhPJx2AuJy+QcrAabTMb6vCZNPkX02N/uNR4+C15e6Iu9I+hPt4usCsK7v1wJ/eTUYdqctv9P8j2XhiTCfUUNkhbA= X-Received: by 2002:a05:6808:1188:: with SMTP id j8mr2716171oil.101.1643053036285; Mon, 24 Jan 2022 11:37:16 -0800 (PST) MIME-Version: 1.0 References: <87bl0amc6s.fsf@x1.stackframe.org> <20220118103323.4bae3a7d@eldfell> <20220118095352.xsb6fqacw4p276c5@sirius.home.kraxel.org> In-Reply-To: From: Daniel Vetter Date: Mon, 24 Jan 2022 20:37:04 +0100 Message-ID: Subject: Re: [PATCH] MAINTAINERS: Add Helge as fbdev maintainer To: Geert Uytterhoeven Content-Type: text/plain; charset="UTF-8" X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Linux Fbdev development list , Helge Deller , Linux Kernel Mailing List , DRI Development , Gerd Hoffmann , Thomas Zimmermann , Sven Schnelle Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Mon, Jan 24, 2022 at 7:51 PM Geert Uytterhoeven wrote: > > Hi Daniel, > > On Thu, Jan 20, 2022 at 1:33 PM Daniel Vetter wrote: > > But reading code&docs is too hard I guess, safer to assume it's just > > broken and not supported. > > I confirm there's lots of documentation (and even more code ;-), > which is always great! > But both are intimidating to me, and most of the documentation covers > features I'm not interested in, as they're only applicable to fancy > modern truecolor 3D-capable multi-buffer and multi-head hardware, while > what I am looking for is usually not documented. E.g. I had a hard > time to discover how color look-up tables work (gamma_{store,size}!), > as this is not covered in https://docs.kernel.org/gpu/index.html, > and none of the tinydrm drivers support CLUT modes. Hm yeah that part is a bit awkward since due to how Xorg works here the gamma table is abused to be the lookup table for C8. If we're adding piles of new Cx formats it might be worth it to structure this a bit better, e.g. (really just thinking on the spot here): - have a separate Cx lookup table blob in drm_plane_state (in theory you could have a different one on each plane and still have an overall gamma ramp on the crtc) - change the compat functions which map the legacy gamma ramp to redirect to the plane gamma ramp if the primary plane is set to Cx - bonus points for then correctly sizing the lookup table to match the number of bits in the Cx plane format But unfiddling this confusion properly is going to be tricky. I think just continuing the tradition we have for C8 and reusing the crtc gamma ramp for that is probably fine for now. And yes that's not documented, because when we fixed the docs for the entire degamm/CGM/gamma color correction pipeline Cx wasn't the top priority :-) Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch 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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A5CE5C433FE for ; Mon, 24 Jan 2022 20:38:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1386436AbiAXUfa (ORCPT ); Mon, 24 Jan 2022 15:35:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34352 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353760AbiAXUNr (ORCPT ); Mon, 24 Jan 2022 15:13:47 -0500 Received: from mail-oi1-x22c.google.com (mail-oi1-x22c.google.com [IPv6:2607:f8b0:4864:20::22c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EFB2BC0604D9 for ; Mon, 24 Jan 2022 11:37:16 -0800 (PST) Received: by mail-oi1-x22c.google.com with SMTP id s9so27115347oib.11 for ; Mon, 24 Jan 2022 11:37:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6T+a8Bx06xvDutb5+VHfkoYO4ESKNGds/DLEsaoyVx8=; b=FMSnFxr7XrvMSHM8YrAM6NA5d3ET8kIpzVnWIzWt1EKy7/wkEHXze29Yi49fGJq+Y5 GnxGPakbkFU5mIiNUV80zkvcs5Lq3FDyau5p4lc5ZHUMincF4tlOGxC64RcVK/YGhUhh TA7kmVkXemc68K3B6H4WUIdjUnrcj0Z5AQRok= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=6T+a8Bx06xvDutb5+VHfkoYO4ESKNGds/DLEsaoyVx8=; b=USjnHWCAHxFR2z+6VYgIrxV1MD84Ilax/Vh67XgRu67jAj6Xy0gF93VfHqSz3ofEjU chbsVld2aR6OGnBK6h6ErRyDDn2l4SD0ZENuwq3FuWI/rGzERjTLpDKmB1VweQBAXb/V 2KBA8Bowd2Lga5NU7UbGbR2J0emjKZ/YyTn5hMx8IOq73X76OGHjnDBDpbKXd0SxvoN5 EWnSz34f+0+beOIqUw4pK1p0wBlGL9O0urFG5qY8+7Ub0JtC+WLPUDucSIuLialu2DQ/ 4wGUgSx+vidKwAQkkDtOa/ygmY5wPNDIPETSP536joPowBlgUi9CUy40xDTWi20xO4/r 8YTQ== X-Gm-Message-State: AOAM532z/O1bQyQtPqKHuvKwI1A//B3IYKZfyxr6YaGS+6b0xTtLK99/ ufCpkHurba9PlMiXfR8ZhETZH0c7hHJbVoe5FgvMSQ== X-Google-Smtp-Source: ABdhPJx2AuJy+QcrAabTMb6vCZNPkX02N/uNR4+C15e6Iu9I+hPt4usCsK7v1wJ/eTUYdqctv9P8j2XhiTCfUUNkhbA= X-Received: by 2002:a05:6808:1188:: with SMTP id j8mr2716171oil.101.1643053036285; Mon, 24 Jan 2022 11:37:16 -0800 (PST) MIME-Version: 1.0 References: <87bl0amc6s.fsf@x1.stackframe.org> <20220118103323.4bae3a7d@eldfell> <20220118095352.xsb6fqacw4p276c5@sirius.home.kraxel.org> In-Reply-To: From: Daniel Vetter Date: Mon, 24 Jan 2022 20:37:04 +0100 Message-ID: Subject: Re: [PATCH] MAINTAINERS: Add Helge as fbdev maintainer To: Geert Uytterhoeven Cc: Gerd Hoffmann , Linux Fbdev development list , Helge Deller , Linux Kernel Mailing List , DRI Development , Thomas Zimmermann , Sven Schnelle Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 24, 2022 at 7:51 PM Geert Uytterhoeven wrote: > > Hi Daniel, > > On Thu, Jan 20, 2022 at 1:33 PM Daniel Vetter wrote: > > But reading code&docs is too hard I guess, safer to assume it's just > > broken and not supported. > > I confirm there's lots of documentation (and even more code ;-), > which is always great! > But both are intimidating to me, and most of the documentation covers > features I'm not interested in, as they're only applicable to fancy > modern truecolor 3D-capable multi-buffer and multi-head hardware, while > what I am looking for is usually not documented. E.g. I had a hard > time to discover how color look-up tables work (gamma_{store,size}!), > as this is not covered in https://docs.kernel.org/gpu/index.html, > and none of the tinydrm drivers support CLUT modes. Hm yeah that part is a bit awkward since due to how Xorg works here the gamma table is abused to be the lookup table for C8. If we're adding piles of new Cx formats it might be worth it to structure this a bit better, e.g. (really just thinking on the spot here): - have a separate Cx lookup table blob in drm_plane_state (in theory you could have a different one on each plane and still have an overall gamma ramp on the crtc) - change the compat functions which map the legacy gamma ramp to redirect to the plane gamma ramp if the primary plane is set to Cx - bonus points for then correctly sizing the lookup table to match the number of bits in the Cx plane format But unfiddling this confusion properly is going to be tricky. I think just continuing the tradition we have for C8 and reusing the crtc gamma ramp for that is probably fine for now. And yes that's not documented, because when we fixed the docs for the entire degamm/CGM/gamma color correction pipeline Cx wasn't the top priority :-) Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch