From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932927Ab1ERQ0A (ORCPT ); Wed, 18 May 2011 12:26:00 -0400 Received: from opensource.wolfsonmicro.com ([80.75.67.52]:55483 "EHLO opensource2.wolfsonmicro.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932387Ab1ERQZ6 (ORCPT ); Wed, 18 May 2011 12:25:58 -0400 Date: Wed, 18 May 2011 09:25:58 -0700 From: Mark Brown To: Linus Walleij Cc: linux-kernel@vger.kernel.org, Bibek BASU , Sascha Hauer , Catalin Marinas , Juergen Beisert , Alan Cox Subject: Re: Smartcard/SIM card subsystem, LDO regulator and signal modelling Message-ID: <20110518162558.GA16414@opensource.wolfsonmicro.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Cookie: Don't read everything you believe. User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 18, 2011 at 12:36:17PM +0200, Linus Walleij wrote: > It's basically an LDO for powering a SIM card (which in turn is basically > a smartcard), but apart from plain regulation also expose some other > electrical properties of the interface to software: > - Select pull-up resistance on some I/O lines > - Select weak pull-down on some data lines > - Select load capacitance limits on the data lines > - Select whether to run in low impedance or transmission gate mode > I think these will be mostly similar so what other SIM card controllers > will need to have. All the stuff needs to have userspace interfaces > since the stuff is usually controlled on behalf of another CPU > running the modem (and also performing the actual traffic on > the SIM data lines). The above also sounds rather like the standard sort of stuff you get with pin muxes - the pulls are certainly very common for random GPIO or I2C use, for example. No real idea on the SIM interface itself.