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 8C004C3DA66 for ; Wed, 23 Aug 2023 23:04:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238845AbjHWXDm (ORCPT ); Wed, 23 Aug 2023 19:03:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51210 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238846AbjHWXDN (ORCPT ); Wed, 23 Aug 2023 19:03:13 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EEB84E6A; Wed, 23 Aug 2023 16:03:10 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 82498630CA; Wed, 23 Aug 2023 23:03:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6046FC433C7; Wed, 23 Aug 2023 23:03:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692831789; bh=3lhGl7dYZSn3kRA3t2GKh2E940LP8kb8mOLoucCwWPQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=vIZu4CTt5nrezgCKEQ+pRV2POGuEUzzVqVUBimkgsO22gS44xhngpdcGSLJVkjssF X3efN0XPNe1n02BE/5vwvI9jxXNtAW5f0PwwxvEKndJZB0B4LsfhGUhq0BiKWMmDoK ftVPWc1R7hLVysLrDBtrkfqW3qHEbGtt2LORX8xsM43GM0Rf2iOecc5HW+FWxmdwc1 mRnE8a1XdZs71A5AgFZWESFkyNgtfQ08pYgoXkWibRvIfhlRYYRgawqqbISundf4qa gbS1cqNCVGdawUC6DqjNxM+uA2QsEPrO4FDzWXAaKmQc0RD8r13hoPYOwUzwtqO2T/ DLhOX8m+yl1yw== Message-ID: <35b28bcb-13ba-fafc-a30b-d84eb3b6bbea@kernel.org> Date: Thu, 24 Aug 2023 08:03:07 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v4 2/2] ata: pata_falcon: add data_swab option to byte-swap disk data Content-Language: en-US To: Sergey Shtylyov , Michael Schmitz , linux-ide@vger.kernel.org, linux-m68k@vger.kernel.org Cc: will@sowerbutts.com, rz@linux-m68k.org, geert@linux-m68k.org, Finn Thain References: <20230822221359.31024-1-schmitzmic@gmail.com> <20230822221359.31024-3-schmitzmic@gmail.com> <56654dc7-37e7-1fd7-0d3f-647563f4cc5a@omp.ru> From: Damien Le Moal Organization: Western Digital Research In-Reply-To: <56654dc7-37e7-1fd7-0d3f-647563f4cc5a@omp.ru> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org On 8/24/23 01:35, Sergey Shtylyov wrote: > On 8/23/23 1:13 AM, Michael Schmitz wrote: > >> Some users of pata_falcon on Q40 have IDE disks in default >> IDE little endian byte order, whereas legacy disks use >> host-native big-endian byte order as on the Atari Falcon. >> >> Add module parameter 'data_swab' to allow connecting drives >> with non-native data byte order. Drives selected by the >> data_swap bit mask will have their user data byte-swapped to >> host byte order, i.e. 'pata_falcon.data_swab=2' will byte-swap >> all user data on drive B, leaving data on drive A in native >> byte order. On Q40, drives on a second IDE interface may be >> added to the bit mask as bits 2 and 3. >> >> Default setting is no byte swapping, i.e. compatibility with >> the native Falcon or Q40 operating system disk format. >> >> Cc: William R Sowerbutts >> Cc: Finn Thain >> Cc: Geert Uytterhoeven >> Tested-by: William R Sowerbutts >> Signed-off-by: Michael Schmitz > > Reviewed-by: Sergey Shtylyov > > [...] > >> diff --git a/drivers/ata/pata_falcon.c b/drivers/ata/pata_falcon.c >> index 3841ea200bcb..7cf15bd9764a 100644 >> --- a/drivers/ata/pata_falcon.c >> +++ b/drivers/ata/pata_falcon.c > [...] >> @@ -194,6 +199,9 @@ static int __init pata_falcon_init_one(struct platform_device *pdev) >> ata_port_desc(ap, "cmd %px ctl %px data %pa", >> base, ctl_base, &ap->ioaddr.data_addr); >> >> + ap->private_data = (void *)(uintptr_t)(pdev->id > 0 ? >> + pata_falcon_swap_mask >> 2 : pata_falcon_swap_mask); > > How about: > > ap->private_data = (void *)(uintptr_t)(pata_falcon_swap_mask >> > (pdev->id > 0 ? 2 : 0)); This is so hard to decode... Let's please spell this out. Something like: int shift; if (pdev->id) shift = 2; else shift = 0; ap->private_data = (uintptr_t)(pata_falcon_swap_mask >> shift); This is initialization, so no need to try to optimize and rather privilege clear code. > > [...] > > MBR, Sergey -- Damien Le Moal Western Digital Research