Return-path: Received: from smtp.codeaurora.org ([198.145.29.96]:51464 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752769AbcHQKb2 (ORCPT ); Wed, 17 Aug 2016 06:31:28 -0400 From: Kalle Valo To: torvalds@linux-foundation.org, akpm@linux-foundation.org, gregkh@linuxfoundation.org, davem@davemloft.net Cc: linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, dinan.gunawardena@netronome.com, Jakub Kicinski Subject: Re: [PATCHv6 1/2] add basic register-field manipulation macros References: <1471360704-10507-1-git-send-email-jakub.kicinski@netronome.com> <1471360704-10507-2-git-send-email-jakub.kicinski@netronome.com> Date: Wed, 17 Aug 2016 13:31:21 +0300 In-Reply-To: <1471360704-10507-2-git-send-email-jakub.kicinski@netronome.com> (Jakub Kicinski's message of "Tue, 16 Aug 2016 16:18:23 +0100") Message-ID: <8737m3bsau.fsf@kamboji.qca.qualcomm.com> (sfid-20160817_123201_762066_2679F75F) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-wireless-owner@vger.kernel.org List-ID: Jakub Kicinski writes: > Common approach to accessing register fields is to define > structures or sets of macros containing mask and shift pair. > Operations on the register are then performed as follows: > > field = (reg >> shift) & mask; > > reg &= ~(mask << shift); > reg |= (field & mask) << shift; > > Defining shift and mask separately is tedious. Ivo van Doorn > came up with an idea of computing them at compilation time > based on a single shifted mask (later refined by Felix) which > can be used like this: > > #define REG_FIELD 0x000ff000 > > field = FIELD_GET(REG_FIELD, reg); > > reg &= ~REG_FIELD; > reg |= FIELD_PUT(REG_FIELD, field); > > FIELD_{GET,PUT} macros take care of finding out what the > appropriate shift is based on compilation time ffs operation. > > GENMASK can be used to define registers (which is usually > less error-prone and easier to match with datasheets). > > This approach is the most convenient I've seen so to limit code > multiplication let's move the macros to a global header file. > Attempts to use static inlines instead of macros failed due > to false positive triggering of BUILD_BUG_ON()s, especially with > GCC < 6.0. > > Signed-off-by: Jakub Kicinski > Reviewed-by: Dinan Gunawardena Are people ok with this? I think they are useful and I can take these through my tree, but I would prefer to get an ack from other maintainers first. Dave? Andrew? Full patches here: https://patchwork.kernel.org/patch/9284153/ https://patchwork.kernel.org/patch/9284155/ -- Kalle Valo