From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (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 73089136358 for ; Wed, 15 Jan 2025 14:34:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736951658; cv=none; b=pXh6bd2/l9ETWKPFRjNA70nhbvIQPavRDHKNtD8Cn966MH1Roay8feuyGO9wT119BPtgHZGhX1izzjjlNMbBja/b772YXPGD8K1G0OiY1V8r1uvxafp+oXonDm2b5A6y7vl5tBesEG4BM9AslhMVUUHvkrXim1DASKc86Gl3tOY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736951658; c=relaxed/simple; bh=+BwkqpgMdP4nryge8XAwlr3ocnpSp93kPfK5dvvQhJ0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=s7k8tKSzF6Q4gVTGb7xMXb3h4i9C3EAzyxCg0d5BjjcpcrPUKiwjD5qIylGVQTZBSPVL65ot0aVNUKyzN7pVEpgLsWSk7M0LTdC16TnpQUv5QCNkubmgJxDSDrYlQL024YzsKR71o3CnP7iN8dKfNrhlsdyxE2t1bN2BJ6v3hW4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=QnVZ92kt; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="QnVZ92kt" Received: from [192.168.88.20] (91-158-153-178.elisa-laajakaista.fi [91.158.153.178]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 0EDDC526; Wed, 15 Jan 2025 15:33:14 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1736951595; bh=+BwkqpgMdP4nryge8XAwlr3ocnpSp93kPfK5dvvQhJ0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=QnVZ92ktu9XV19uGghR+pXIGNZHKmpNfERPTx2PF0SFcdW2V4R70TgSYAhSJVQzgk ilP1mAtlbiYM18tY7IHgyLvryoIIAW2bhlY+EQurqMEtd/FPj/iEHsI2HATgodbh3a 76PagALDfywQFrskQsb5P96lsmEx5hyKdm8Uh7BM= Message-ID: <0004c685-b8c6-4df1-acb4-7c80a9d3255e@ideasonboard.com> Date: Wed, 15 Jan 2025 16:34:09 +0200 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 v2 04/10] drm/fourcc: Add DRM_FORMAT_Y10_LE32 To: Geert Uytterhoeven Cc: Vishal Sagar , Anatoliy Klymenko , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Laurent Pinchart , Michal Simek , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20250115-xilinx-formats-v2-0-160327ca652a@ideasonboard.com> <20250115-xilinx-formats-v2-4-160327ca652a@ideasonboard.com> <6b084e2c-100f-4563-8797-9fd6c862ed0c@ideasonboard.com> <0b0decd1-6f19-424a-84e5-fc71dceb983c@ideasonboard.com> Content-Language: en-US From: Tomi Valkeinen Autocrypt: addr=tomi.valkeinen@ideasonboard.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 15/01/2025 16:08, Geert Uytterhoeven wrote: > Hi Tomi, > > On Wed, Jan 15, 2025 at 2:46 PM Tomi Valkeinen > wrote: >> On 15/01/2025 14:52, Geert Uytterhoeven wrote: >>> On Wed, Jan 15, 2025 at 1:42 PM Tomi Valkeinen >>> wrote: >>>> On 15/01/2025 14:33, Geert Uytterhoeven wrote: >>>>> On Wed, Jan 15, 2025 at 12:11 PM Tomi Valkeinen >>>>> wrote: >>>>>> On 15/01/2025 12:33, Geert Uytterhoeven wrote: >>>>>>> On Wed, Jan 15, 2025 at 10:04 AM Tomi Valkeinen >>>>>>> wrote: >>>>>>>> Add Y10_LE32, a 10 bit greyscale format, with 3 pixels packed into >>>>>>>> 32-bit container. >>>>>>>> >>>>>>>> Signed-off-by: Tomi Valkeinen >>>>>>> >>>>>>> Thanks for your patch! >>>>>>> >>>>>>>> --- a/include/uapi/drm/drm_fourcc.h >>>>>>>> +++ b/include/uapi/drm/drm_fourcc.h >>>>>>>> @@ -408,6 +408,7 @@ extern "C" { >>>>>>>> /* Greyscale formats */ >>>>>>>> >>>>>>>> #define DRM_FORMAT_Y8 fourcc_code('G', 'R', 'E', 'Y') /* 8-bit Y-only */ >>>>>>>> +#define DRM_FORMAT_Y10_LE32 fourcc_code('Y', 'P', 'A', '4') /* [31:0] x:Y2:Y1:Y0 2:10:10:10 little endian */ >>>>>>> >>>>>>> R10_LE32? Or R10_PA4? >>>>>> >>>>>> Can we discuss the "R" vs "Y" question under the cover letter? There's >>>>>> some more context about it in there. >>>>> >>>>> Sorry, hadn't read the cover letter. I got attracted by "Y8" and "Y10". >>>>> >>>>>> I took the "LE32" from Gstreamer's format. Maybe it's a bit pointless. >>>>>> >>>>>> I don't know if it makes sense to add the fourcc to the DRM format name. >>>>>> The fourcc is very limited. Rather, we could, say, have >>>>>> DRM_FORMAT_Y10_PACKED_32 (or "R", if you insist =). >>>>>> >>>>>>> Does LE32 have a meaning? My first guess just reading the subject >>>>>>> was wrong ("little endian 32-bit" ;-) >>>>>> >>>>>> I'm not sure I follow. It's little-endian. The pixel group/unit is a >>>>>> 32-bit number, where the leftmost pixel on the screen is in bits 9-0, >>>>>> and the padding is in bits 31-30, and stored in memory as little-endian. >>>>> >>>>> Ah, the "LE" applies to the pixels inside each word. >>>> >>>> No, to the 32-bit container. >>>> >>>>> DRM formats stored in memory are always little-endian, unless the >>>>> DRM_FORMAT_BIG_ENDIAN bit is set, which is what I was hinting >>>>> at... >>>> >>>> Indeed you're right. The "LE" is pointless. So back to the bike-shedding >>>> about the name =). >>> >>> As the order inside the container is Y2:Y1:Y0, it _is_ little endian. >>> Cfr. >>> >>> #define DRM_FORMAT_YUYV fourcc_code('Y', 'U', 'Y', 'V') /* [31:0] >>> Cr0:Y1:Cb0:Y0 8:8:8:8 little endian */ >> >> Hmm, I see. I hadn't thought LE in that context, but I think it makes >> sense when there are multiple pixels in one container. So the "little >> endian" above would refer to the order of Y1 and Y0. So is Y1 the >> least-significant-pixel? =) > > No, Y0 is the least-significant member of the container, which > corresponds to the first pixel ("little end first"). In the number 0x1234, 0x34 is the least-significant byte, and stored first in memory in little endian. So, similarly, with Y0:Y1, Y1 is stored first in little-endian order, so it's the least-significant-pixel =). >> But, say, in >> >> #define DRM_FORMAT_RG88 fourcc_code('R', 'G', '8', '8') /* [15:0] R:G >> 8:8 little endian */ >> >> the "little endian" refers to the 16-bit value itself? Which is not >> necessary, as the default assumption is little endian. > > I think so. > >> In any case, when considering your latest point... "LE" in the name >> makes sense? But with a quick look I didn't find any formats that would >> have "big endian pixel order", so maybe we can just assume little endian >> pixel order too. > > [CDR][124] have. See the descriptions of the commits that introduced > them for the rationale behind this: > > b92db7e4fe740daa drm/fourcc: Add DRM_FORMAT_D[1248] > d093100b425df6fe drm/fourcc: Add DRM_FORMAT_R[124] > e5bd7e3e4a68f0be drm/fourcc: Add DRM_FORMAT_C[124] Ah, I see. But they don't call the pixel ordering "big endian". Well, this is all somewhat beside the point. So is "_Y10_32" (or "_R10_32" if we use R) fine? Tomi