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 A701CEE49A4 for ; Tue, 22 Aug 2023 11:46:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235187AbjHVLqG (ORCPT ); Tue, 22 Aug 2023 07:46:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43612 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234461AbjHVLqG (ORCPT ); Tue, 22 Aug 2023 07:46:06 -0400 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB1EFE7F; Tue, 22 Aug 2023 04:45:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1692704740; x=1724240740; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=yWJeFjh0gbuONuUENqg06iKxJfhh+cE8CuDrcCOmYDk=; b=GtSGpWMv0q7QXVjlhtikWpntEz20sK+RQdtDP3EmJzWNkPRtOXdVPWai suMjGEbwsC1tfcJOqoI5yZzMmaWVWqHsuAFIFWyEUTI7EfHfQAk798j7K Gj2XVQVNk8nz1KjwS1ID1NwkXQwa1N0ILuy7+1/LUpZVbePQzLd4yAnra AKX9DH4VC7wCJN50gDcq+aoLy/AQy/vl8tEDGkzsGRqU9w9e9LbGc1iPZ mPQT535/njqTWKrMxih8iqHQesZXKw/oqQfVbZzuKzxp6oVOUH+Xy9uSg E1S4Iv66smM4D6F1pZsT4Oy77r6Khge5VOBiNbletbSeLUpmdC7zBA9Fo A==; X-IronPort-AV: E=McAfee;i="6600,9927,10809"; a="404858534" X-IronPort-AV: E=Sophos;i="6.01,192,1684825200"; d="scan'208";a="404858534" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Aug 2023 04:44:50 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10809"; a="736182765" X-IronPort-AV: E=Sophos;i="6.01,192,1684825200"; d="scan'208";a="736182765" Received: from smile.fi.intel.com ([10.237.72.54]) by orsmga002.jf.intel.com with ESMTP; 22 Aug 2023 04:44:46 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.96) (envelope-from ) id 1qYPoS-008eMe-1r; Tue, 22 Aug 2023 14:44:44 +0300 Date: Tue, 22 Aug 2023 14:44:44 +0300 From: Andy Shevchenko To: Geert Uytterhoeven Cc: Biju Das , Guenter Roeck , Heikki Krogerus , Greg Kroah-Hartman , linux-usb@vger.kernel.org, Geert Uytterhoeven , Dmitry Torokhov , Andi Shyti , linux-renesas-soc@vger.kernel.org, "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Rob Herring , Conor Dooley , Frank Rowand Subject: Re: [PATCH 2/4] usb: typec: tcpci_rt1711h: Convert enum->pointer for data in the match tables Message-ID: References: <20230820184402.102486-1-biju.das.jz@bp.renesas.com> <20230820184402.102486-3-biju.das.jz@bp.renesas.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Tue, Aug 22, 2023 at 09:21:19AM +0200, Geert Uytterhoeven wrote: > On Mon, Aug 21, 2023 at 7:09 PM Andy Shevchenko > wrote: > > On Mon, Aug 21, 2023 at 05:40:05PM +0200, Geert Uytterhoeven wrote: > > > On Mon, Aug 21, 2023 at 5:25 PM Andy Shevchenko > > > wrote: > > > > On Mon, Aug 21, 2023 at 03:27:43PM +0200, Geert Uytterhoeven wrote: > > > > > On Mon, Aug 21, 2023 at 3:04 PM Andy Shevchenko > > > > > wrote: > > > > > > On Sun, Aug 20, 2023 at 07:44:00PM +0100, Biju Das wrote: ... > > > > > > For all your work likes this as I noted in the reply to Guenter that > > > > > > the couple of the selling points here are: > > > > > > 1) avoidance of the pointer abuse in OF table > > > > > > (we need that to be a valid pointer); > > > > > > > > > > There is no pointer abuse: both const void * (in e.g. of_device_id) > > > > > and kernel_ulong_t (in e.g. i2c_device_id) can be used by drivers > > > > > to store a magic cookie, being either a pointer, or an integer value. > > > > > The same is true for the various unsigned long and void * "driver_data" > > > > > fields in subsystem-specific driver structures. > > > > > > > > (void *)5 is the abuse of the pointer. > > > > We carry something which is not a valid pointer from kernel perspective. > > > > > > But the data field is not required to be a valid pointer. > > > What kind and type of information it represents is specific to the driver. > > > > Where to find necessary information which is not always an integer constant. > > For example, for the driver data that has callbacks it can't be invalid pointer. > > If the driver uses it to store callbacks, of course it needs to be a > valid pointer. But that is internal to the driver. It is not that > we're passing random integer values to a function that expects a > pointer that can actually be dereferenced. > > > Since OF ID table structure is universal, it uses pointers. Maybe you need to > > update it to use plain integer instead? > > It is fairly common in the kernel to use void * to indicate a > driver-specific cookie, being either a real pointer or an integral > value, that is passed verbatim. See also e.g. the "dev" parameter > of request_irq(). Yes, that parameter is void * due to calling kfree(free_irq(...)). So, that's argument for my concerns. > > I think there is no more sense to continue this. We have to admit we have > > a good disagreement on this and I do not see any way I can agree with your > > arguments. Note, I'm fine if you "fix" OF ID structure to use kernel_ulong_t. > > of_device_id is also used in userspace (e.g. modutils), but I believe > that uses a copy of the structure definition, not the definition from > the kernel headers. Nope, it uses the very same mod_devicetable.h in both. > Still, changing the type would be a lot of work, > for IMHO no real gain. So, stale mate here, then? > > The only objection there is that it may not carry on the const qualifier, > > which I personally find being a huge downside of the whole driver_data. > > I believe you haven't objected that. > > Having const is nice, indeed. At least something we have agreed on :-) -- With Best Regards, Andy Shevchenko