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 93BDAC38145 for ; Wed, 7 Sep 2022 12:21:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229494AbiIGMVm (ORCPT ); Wed, 7 Sep 2022 08:21:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34612 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229464AbiIGMVk (ORCPT ); Wed, 7 Sep 2022 08:21:40 -0400 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A1924AB197; Wed, 7 Sep 2022 05:21:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1662553299; x=1694089299; h=date:from:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=i5as+3xhYVCZyfsyjas1dxePnfSBwW/4rUe+OF92EJg=; b=PswZREPHRKtqu4mITUeMg0f8+2FUiQGSLe5GY7nc1CgbqOqRQPD7Qz+N 9XvXtkRCAciiNLMPBeNJd+SLRh5Hlp16nex/DDDBTdQ6Nwx7BdE3YKgoP wrl5XR8EUvs7Por1km9MqqoY6uuHDWN4VAOzj5ptxQueoUSSgnBBaflMy NZu8zz2C2fVIOL7oe6wrfAtKGEDTOch8NeYmYP3HrCCQPPBntBrX1nY2/ lkvd9E/SNIzNzOXdmgNM59J11ix2MVCv+aituNenb0z1tivJE2ZSWtzoU q+Yakdz96dkYDy+rqQzsrL8TgKgEnq9NUN05q58u8nSOu0FI/pdMz3wIp g==; X-IronPort-AV: E=McAfee;i="6500,9779,10462"; a="360801557" X-IronPort-AV: E=Sophos;i="5.93,296,1654585200"; d="scan'208";a="360801557" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Sep 2022 05:21:39 -0700 X-IronPort-AV: E=Sophos;i="5.93,296,1654585200"; d="scan'208";a="644594732" Received: from dmatouse-mobl.ger.corp.intel.com ([10.251.223.53]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Sep 2022 05:21:30 -0700 Date: Wed, 7 Sep 2022 15:21:28 +0300 (EEST) From: =?ISO-8859-15?Q?Ilpo_J=E4rvinen?= To: Arnd Bergmann cc: Jiri Slaby , Johan Hovold , Greg Kroah-Hartman , linux-serial , LKML , Tobias Klauser , Richard Genoud , Nicolas Ferre , Alexandre Belloni , Claudiu Beznea , Vladimir Zapolskiy , Liviu Dudau , Sudeep Holla , Lorenzo Pieralisi , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , NXP Linux Team , =?ISO-8859-15?Q?Andreas_F=E4rber?= , Manivannan Sadhasivam , Russell King , Florian Fainelli , bcm-kernel-feedback-list@broadcom.com, =?ISO-8859-15?Q?Pali_Roh=E1r?= , Kevin Cernekee , Palmer Dabbelt , Paul Walmsley , Orson Zhai , Baolin Wang , Chunyan Zhang , Patrice Chotard , linux-riscv@lists.infradead.org Subject: Re: [PATCH v3 0/4] tty: TX helpers In-Reply-To: <715b40ba-1bcc-4582-bed1-ef41126c7b94@www.fastmail.com> Message-ID: References: <20220906104805.23211-1-jslaby@suse.cz> <4e9b4471-a6f2-4b16-d830-67d253ae4e6a@linux.intel.com> <715b40ba-1bcc-4582-bed1-ef41126c7b94@www.fastmail.com> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="8323329-1356709510-1662553299=:1717" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-1356709510-1662553299=:1717 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT On Wed, 7 Sep 2022, Arnd Bergmann wrote: > On Wed, Sep 7, 2022, at 12:16 PM, Ilpo Järvinen wrote: > > On Wed, 7 Sep 2022, Jiri Slaby wrote: > >> On 06. 09. 22, 13:30, Johan Hovold wrote: > >> > On Tue, Sep 06, 2022 at 12:48:01PM +0200, Jiri Slaby wrote: > >> > NAK > >> > >> I'd love to come up with something nicer. That would be a function in > >> serial-core calling hooks like I had [1] for example. But provided all those > >> CPU workarounds/thunks, it'd be quite expensive to call two functions per > >> character. > >> > >> Or creating a static inline (having ± the macro content) and the hooks as > >> parameters and hope for optimizations to eliminate thunks (also suggested in > >> the past [1]). > >> > >> [1] https://lore.kernel.org/all/20220411105405.9519-1-jslaby@suse.cz/ > > > > I second Jiri here. > > > > Saving lines in drivers is not that important compared with all removing > > all the variants of the same thing that have crept there over the years. > > > > I suspect the main reason for the variants is that everybody just used > > other drivers as examples and therefore we've a few "main" variant > > branches depending on which of the drivers was used as an example for the > > other. That is hardly a good enough reason to keep them different and as > > long as each driver keeps its own function for this, it will eventually > > lead to similar differentiation so e.g. a one-time band-aid similarization > > would not help in the long run. > > > > Also, I don't understand why you see it unreadable when the actual code is > > out in the open in that macro. It's formatted much better than e.g. > > read_poll_timeout() if you want an example of something that is hardly > > readable ;-). I agree though there's a learning-curve, albeit small, that > > it actually creates a function but that doesn't seem to me as big of an > > obstacle you seem to think. > > I think it would help to replace the macro that defines > the function with a set of macros that can be used in > function bodies. This would avoid the __VA_ARGS__ stuff > and allow readers that are unfamiliar with tty drivers to > treat it as a function call. > > So e.g. instead of > > static DEFINE_UART_PORT_TX_HELPER_LIMITED(altera_jtaguart_do_tx_chars, > true, > writel(ch, port->membase + ALTERA_JTAGUART_DATA_REG), > ({})); > > the altera_jtaguart driver would contain a function like > > static int altera_jtaguart_do_tx_chars(struct uart_port *port, > unsigned int count) > { > char ch; > > return uart_port_tx_helper_limited(port, ch, count, true, > writel(ch, port->membase + ALTERA_JTAGUART_DATA_REG), > ({})); > } > > or some variation of that. It's a few more lines, but those > extra lines would help me understand what is actually going on > while still avoiding the usual bugs and duplication. > > If the caller of that function is itself trivial (like > serial21285_tx_chars), then the intermediate function can > be omitted in order to save some of the extra complexity. I'd be ok with that. There's still a small startle factor associated to passing that writel(...) as an argument to a "function" but it's the same for other things such as read_poll_timeout() so not an end of the world. -- i. --8323329-1356709510-1662553299=:1717--