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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 23188C4360C for ; Thu, 10 Oct 2019 06:29:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EBDF920B7C for ; Thu, 10 Oct 2019 06:29:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732917AbfJJG3b (ORCPT ); Thu, 10 Oct 2019 02:29:31 -0400 Received: from mail-oi1-f195.google.com ([209.85.167.195]:36687 "EHLO mail-oi1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726983AbfJJG3b (ORCPT ); Thu, 10 Oct 2019 02:29:31 -0400 Received: by mail-oi1-f195.google.com with SMTP id k20so3945959oih.3; Wed, 09 Oct 2019 23:29:30 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=+Cx2nK6QRBgJuBNcUtpzK8FDH7ngKKIhRfZFf1NmTFQ=; b=kHPIj9KjP0SBjIgczu72EL/eRPNB35Ybua9nkVZSeG5OKbrLqXPWK4rRquBMLAluyK EVb5jjYJvHYTkt1XmoB+2kbtcVEDyuyVkaVu+YNHY65wkCjFVGVcIFbErLVIZlfdYFV1 +ULDkchJXV5Sfe6wkuWn6PkGeAKVPvmutHcnlh1r6lQrEkraXax7ZbIpKXDpYbIGpOvn AmmKuugV6T3g9exwUOIJt3kK1/b5pj9oeFIYRfUJFMWwFxKyeGo4YJPR2yHaVDeKl1Jd UTVfZa725Oe45w1o7xout7BhvtvvIQ14ys0keOtbL9MgfVw5wCvybKXtT4okRea88r13 RdiA== X-Gm-Message-State: APjAAAXoF2R7ndOyiWKrqGvIFKAii27vIQwg76UOjN7hKgQxg1Vl7m4j JnXGqeWUZ1SiKlMt93PgcZqCZ8nxYu20fQP/rDc= X-Google-Smtp-Source: APXvYqxmAwoB1fEOxz3+Xl/nikYsLddSYKE5o75tBiCX/ExRRXKw9htkShc664JHnVxtveTq0QU4eZt/Zpliy/z2V/0= X-Received: by 2002:a05:6808:3b4:: with SMTP id n20mr5863396oie.131.1570688969834; Wed, 09 Oct 2019 23:29:29 -0700 (PDT) MIME-Version: 1.0 References: <893c3b4f03266c9496137cc98ac2b1bd27f92c73.1570633189.git.vilhelm.gray@gmail.com> <20191009170917.GG32742@smile.fi.intel.com> In-Reply-To: From: Geert Uytterhoeven Date: Thu, 10 Oct 2019 08:29:17 +0200 Message-ID: Subject: Re: [PATCH v17 01/14] bitops: Introduce the for_each_set_clump8 macro To: Andy Shevchenko Cc: Masahiro Yamada , Andy Shevchenko , William Breathitt Gray , Linus Walleij , Bartosz Golaszewski , Andrew Morton , "open list:GPIO SUBSYSTEM" , Linux Kernel Mailing List , linux-arch , Rasmus Villemoes , linux-arm-kernel , Linux PM mailing list , Phil Reid , Lukas Wunner , sean.nyekjaer@prevas.dk, morten.tiljeset@prevas.dk, Arnd Bergmann Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Andy, On Thu, Oct 10, 2019 at 7:49 AM Andy Shevchenko wrote: > On Thu, Oct 10, 2019 at 5:31 AM Masahiro Yamada > wrote: > > On Thu, Oct 10, 2019 at 3:54 AM Geert Uytterhoeven wrote: > > > On Wed, Oct 9, 2019 at 7:09 PM Andy Shevchenko > > > wrote: > > > > On Thu, Oct 10, 2019 at 01:28:08AM +0900, Masahiro Yamada wrote: > > > > > On Thu, Oct 10, 2019 at 12:27 AM William Breathitt Gray > > > > > wrote: > > > > > > > > > > > > This macro iterates for each 8-bit group of bits (clump) with set bits, > > > > > > within a bitmap memory region. For each iteration, "start" is set to the > > > > > > bit offset of the found clump, while the respective clump value is > > > > > > stored to the location pointed by "clump". Additionally, the > > > > > > bitmap_get_value8 and bitmap_set_value8 functions are introduced to > > > > > > respectively get and set an 8-bit value in a bitmap memory region. > > > > > > > > > Why is the return type "unsigned long" where you know > > > > > it return the 8-bit value ? > > > > > > > > Because bitmap API operates on unsigned long type. This is not only > > > > consistency, but for sake of flexibility in case we would like to introduce > > > > more calls like clump16 or so. > > > > > > TBH, that doesn't convince me: those functions explicitly take/return an > > > 8-bit value, and have "8" in their name. The 8-bit value is never > > > really related to, retrieved from, or stored in a full "unsigned long" > > > element of a bitmap, only to/from/in a part (byte) of it. > > > > > > Following your rationale, all of iowrite{8,16,32,64}*() should take an > > > "unsigned long" value, too. > > > > > > > +1 > > > > Using u8/u16/u32/u64 looks more consistent with other bitmap helpers. > > > > void bitmap_from_arr32(unsigned long *bitmap, const u32 *buf, unsigned > > int nbits); > > void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, unsigned int nbits); > > static inline void bitmap_from_u64(unsigned long *dst, u64 mask); > > > > > > > > If you want to see more examples from other parts, > > Geert's and yours examples both are not related. They are about > fixed-width properies when we know that is the part of protocol. > Here we have no protocol which stricts us to the mentioned fixed-width types. Yes you have: they are functions to store/retrieve an 8-bit value from the middle of the bitmap, which is reflected in their names ("clump8", "value8"). The input/output value is clearly separated from the actual bitmap, which is referenced by the "unsigned long *". If you add new "value16" functions, they will be intended to store/retrieve 16-bit values. Besides, if retrieving an 8-bit value requires passing an "unsigned long *", the caller needs two variables: one unsigned long to pass the address of, and one u8 to copy the returned value into. > So, I can tell an opposite, your arguments didn't convince me. > > Imagine the function which does an or / and / xor operation on bitmap. > Now, when I supply unsigned long, I will see > operations on one type in _one_ function independently of the size. > Your proposal will make an unneded churn. Depends on what kind of value you will use to do the logical operation with the bitmap: - Full bitmap => unsigned long * + size, - Single bitmap "word" => unsigned long, - 8-bit value => u8, - 16-bit value => u16 Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds