Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1169499AbdDXMFK (ORCPT ); Mon, 24 Apr 2017 08:05:10 -0400 Received: from mezzanine.sirena.org.uk ([106.187.55.193]:46788 "EHLO mezzanine.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1169468AbdDXMFC (ORCPT ); Mon, 24 Apr 2017 08:05:02 -0400 Date: Mon, 24 Apr 2017 13:04:51 +0100 From: Mark Brown To: Charles Keepax Cc: Variksla , linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org Message-ID: <20170424120451.dw5nhdpockesrg3n@sirena.org.uk> References: <20170421172709.dqz7vq3vor56a5qg@sirena.org.uk> <20170424090231.GF1594@localhost.localdomain> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="6fg5njh53fvztt6x" Content-Disposition: inline In-Reply-To: <20170424090231.GF1594@localhost.localdomain> X-Cookie: To err is human, to moo bovine. User-Agent: NeoMutt/20170306 (1.8.0) X-SA-Exim-Connect-IP: 2001:470:1f1d:6b5::3 X-SA-Exim-Mail-From: broonie@sirena.org.uk Subject: Re: bug fix for registers debugfs file implementation [RFC] X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: No (on mezzanine.sirena.org.uk); Unknown failure Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1678 Lines: 40 --6fg5njh53fvztt6x Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Mon, Apr 24, 2017 at 10:02:31AM +0100, Charles Keepax wrote: > On Sat, Apr 22, 2017 at 01:28:15PM -0700, Variksla wrote: > > > On Apr 21, 2017, at 10:27 AM, Mark Brown wrote: > > > If I remember correctly this is done the way it is because seq_file has > > > to iterate through the entire file to get to the point being read by the > > > application. This is a *very* big overhead for some applications (like > > > monitoring some registers to see what they're doing) on bigger devices, > > Wondering why would the user space application be monitoring the registers? > We do have tooling that accesses and occasionally monitors > registers using the debugfs files. It is often used by hardware > types while testing/debugging issues. And as Mark points out Even without an actual program explicitly written for it interactive monitoring of the register map can be done by a person as well which is just as much of an application (and the major point of the file). --6fg5njh53fvztt6x Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAlj96eIACgkQJNaLcl1U h9C4hAf+J8jgbzC9S3m3nZd3WE4Yvj/PXyh8+V1B7U48Vn6IPYDyPvnAe8B82Egf 43/6GFgZ5RmlOfItaW/5nJepG2qCbWOTJd6vu3VXD76rM0Evs9TkoGhUYm6KoE44 HxBVTK6SEtgD8DKPGv5Spu6YhS1usXAZJfaWl9Q9gFJzYKYJfBwLX2kAONUd0XaN V2jlZ0OHB7dAy2S20K2kGQpmepghO0x/mz6BM9fcxVLSJZ4ykAwYKjbtlwa3g/gA KgUF61HRqmZJIK9OdJ4ObnRLdNHq1iDnAIs3T+Yxj7elpIzMMOIFcmqBYnVJIxGw hsa6zk+rt4+P1O0m+gPY9HRjkIFBGg== =VVT2 -----END PGP SIGNATURE----- --6fg5njh53fvztt6x--