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 69665C4167D for ; Thu, 2 Nov 2023 08:25:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234637AbjKBIZk (ORCPT ); Thu, 2 Nov 2023 04:25:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47380 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233226AbjKBIZk (ORCPT ); Thu, 2 Nov 2023 04:25:40 -0400 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.65]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 601FC111; Thu, 2 Nov 2023 01:25:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1698913534; x=1730449534; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=ZJhkKBusAN3Lj8x111ENUnQiThkfM+G/Nik1BoS7pz4=; b=gZ/M9W4erGiwZ5Jfin/vZJlhUsLFadcwyWPqMhPZsVkYWJHVz5uuM2dY z9StfjA1MB9sk1kYYa+j5wVL9WEIFA3sJh2pQS+Ac3v9fOlP7REuipeLu OlmaxPZLwcSsx/Z85pWrjOrryvJ0+WXMUgwA+Saydpffrg6XiG9JNYYTM V4hL1AF4uUu4tHWAWcJ9ntjS95/yB2QEdYcyuVU49JRWDn/Fuv0u6jmSf yrNeB33JNgiUmB0/pdYT4NG8QO+72d29vbhA99XBdpHi23sQ0/CtSedaR 98t1bOUfEfjkIMUapTfUC2LaxGmZR9jUuBajf18qNaOlV/5A2DZVkPxEx A==; X-IronPort-AV: E=McAfee;i="6600,9927,10881"; a="392548209" X-IronPort-AV: E=Sophos;i="6.03,270,1694761200"; d="scan'208";a="392548209" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Nov 2023 01:25:33 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10881"; a="934709479" X-IronPort-AV: E=Sophos;i="6.03,270,1694761200"; d="scan'208";a="934709479" Received: from turnipsi.fi.intel.com (HELO kekkonen.fi.intel.com) ([10.237.72.44]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Nov 2023 01:25:32 -0700 Received: from kekkonen.localdomain (localhost [127.0.0.1]) by kekkonen.fi.intel.com (Postfix) with SMTP id A25C511F9E8; Thu, 2 Nov 2023 10:25:28 +0200 (EET) Date: Thu, 2 Nov 2023 08:25:28 +0000 From: Sakari Ailus To: Alexander Stein Cc: Laurent Pinchart , Mauro Carvalho Chehab , Manivannan Sadhasivam , Hans de Goede , linux-media@vger.kernel.org, Alain Volmat , stable@vger.kernel.org Subject: Re: [PATCH v2 1/2] media: v4l2-cci: Add support for little-endian encoded registers Message-ID: References: <20231101122354.270453-1-alexander.stein@ew.tq-group.com> <20231102012217.GC5933@pendragon.ideasonboard.com> <4980064.31r3eYUQgx@steina-w> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4980064.31r3eYUQgx@steina-w> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Hi Alexander, On Thu, Nov 02, 2023 at 08:51:12AM +0100, Alexander Stein wrote: > Hi, > > thanks for the feedback. > > Am Donnerstag, 2. November 2023, 07:30:44 CET schrieb Sakari Ailus: > > Hi Laurent, > > > > On Thu, Nov 02, 2023 at 03:22:17AM +0200, Laurent Pinchart wrote: > > > Hi Alexander, > > > > > > Thank you for the patch. > > > > > > On Wed, Nov 01, 2023 at 01:23:53PM +0100, Alexander Stein wrote: > > > > Some sensors, e.g. Sony, are using little-endian registers. Add support > > > > for > > > > > > I would write Sony IMX290 here, as there are Sony sensors that use big > > > endian. > > > > Almost all of them. There are a few exceptions indeed. This seems to be a > > bug. > > Let's name IMX290 here as an actual example. No need to worry about other > models here. > > > > > those by encoding the endianess into Bit 20 of the register address. > > > > > > > > Fixes: af73323b97702 ("media: imx290: Convert to new CCI register access > > > > helpers") Cc: stable@vger.kernel.org > > > > Signed-off-by: Alexander Stein > > > > --- > > > > > > > > drivers/media/v4l2-core/v4l2-cci.c | 44 ++++++++++++++++++++++++------ > > > > include/media/v4l2-cci.h | 5 ++++ > > > > 2 files changed, 41 insertions(+), 8 deletions(-) > > > > > > > > diff --git a/drivers/media/v4l2-core/v4l2-cci.c > > > > b/drivers/media/v4l2-core/v4l2-cci.c index bc2dbec019b04..673637b67bf67 > > > > 100644 > > > > --- a/drivers/media/v4l2-core/v4l2-cci.c > > > > +++ b/drivers/media/v4l2-core/v4l2-cci.c > > > > @@ -18,6 +18,7 @@ > > > > > > > > int cci_read(struct regmap *map, u32 reg, u64 *val, int *err) > > > > { > > > > > > > > + bool little_endian; > > > > > > > > unsigned int len; > > > > u8 buf[8]; > > > > int ret; > > > > > > > > @@ -25,6 +26,7 @@ int cci_read(struct regmap *map, u32 reg, u64 *val, > > > > int *err)> > > > > > if (err && *err) > > > > > > > > return *err; > > > > > > > > + little_endian = reg & CCI_REG_LE; > > > > > > You could initialize the variable when declaring it. Same below. > > > > I was thinking of the same, but then it'd be logical to move initialisation > > of all related variables there. reg is modified here though. I'd keep > > setting little_endian here. If someone wants to move it, that could be done > > in a separate patch. > > > > > > len = FIELD_GET(CCI_REG_WIDTH_MASK, reg); > > > > reg = FIELD_GET(CCI_REG_ADDR_MASK, reg); > > > > > > > > @@ -40,16 +42,28 @@ int cci_read(struct regmap *map, u32 reg, u64 *val, > > > > int *err)> > > > > > *val = buf[0]; > > > > break; > > > > > > > > case 2: > > > > - *val = get_unaligned_be16(buf); > > > > + if (little_endian) > > > > + *val = get_unaligned_le16(buf); > > > > + else > > > > + *val = get_unaligned_be16(buf); > > > > > > Unrelated to this patch, isn't buf aligned to a 4 bytes boundary ? > > > > Very probably, as it's right after len that's an unsigned int. Adding > > __aligned(8) would ensure we don't need any of the unaligned variants, and > > most likely would keep the stack layout as-is. > > You mean something like this? > > u8 __aligned(8) buf[8]; > [...] > if (little_endian) > *val = le64_to_cpup(buf); > else > *val = be64_to_cpup(buf); > > But what about 24 Bits? There is no le24_to_cpup. I would rather use the same > API for all cases. The aligned APIs are much better choice when you can use them. The 24 bit case can remain special IMO. > > > Or... how about putting it in an union with a u64? That would mean it's > > accessible as u64 alignment-wise while the alignment itself is up to the > > ABI. A comment would be good to have probably. > > An additional union seems a bit too much here. Unless something suitable > already exists for general usage. I think it's nicer than using __aligned() as you get ABI alignment that way, not something you force manually --- that's a bit crude. I wonder that others think. -- Regards, Sakari Ailus