Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755269AbdHYQyK (ORCPT ); Fri, 25 Aug 2017 12:54:10 -0400 Received: from mail-vk0-f46.google.com ([209.85.213.46]:36987 "EHLO mail-vk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754926AbdHYQxm (ORCPT ); Fri, 25 Aug 2017 12:53:42 -0400 X-Google-Smtp-Source: ADKCNb4bATVL3i7hDL9X7s45e8GzsAGibCV26s8Ipe/Q12UMYZMtVLXnNVdcM2gjMKkJU7JxiNsSbFzJjoTaKQ4w4js= MIME-Version: 1.0 In-Reply-To: <593cd0d3-8e06-0992-c155-1322014c0477@longlandclan.id.au> References: <1503418256-5215-1-git-send-email-oleksandrs@mellanox.com> <593cd0d3-8e06-0992-c155-1322014c0477@longlandclan.id.au> From: Rick Altherr Date: Fri, 25 Aug 2017 09:53:40 -0700 Message-ID: Subject: Re: [patch v6 0/3] JTAG driver introduction To: Stuart Longland Cc: Linus Walleij , Oleksandr Shamray , "devicetree@vger.kernel.org" , =?UTF-8?B?SmnFmcOtIFDDrXJrbw==?= , Arnd Bergmann , system-sw-low-level@mellanox.com, Greg KH , OpenBMC Maillist , "linux-kernel@vger.kernel.org" , openocd-devel-owner@lists.sourceforge.net, mec@shout.net, Rob Herring , "linux-serial@vger.kernel.org" , Tobias Klauser , "linux-api@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1112 Lines: 31 On Fri, Aug 25, 2017 at 1:50 AM, Stuart Longland wrote: > [Note: dropping vadimp@maellanox.com as SMTP server complained about the > DNS server returning NXDOMAIN. Apologies.] > On 25/08/17 18:32, Linus Walleij wrote: >> Gnah! >> Whoever writes a slot-in replacement making the character device >> take precendence wins lots of karma. > > What would such a replacement look like though? See Linus's comments about using the existing kernel GPIO chardev interface. It already supports requesting multiple GPIO line state changes in a single request. > > Some sort of system whereby you can read/write single-line commands as > if talking to a GPIO expander over a UART? > > Would you access the GPIOs one by one, or would you perhaps map them > into a bitmap (maybe arbitrarily, up to 64-bits wide) and perform masked > operations on the bitmap? > > I'm no fan of the sysfs GPIO interface, but it beats poking around at > registers behind the kernel's back. > -- > Stuart Longland (aka Redhatter, VK4MSL) > > I haven't lost my mind... > ...it's backed up on a tape somewhere. >