Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934707AbbEMTKw (ORCPT ); Wed, 13 May 2015 15:10:52 -0400 Received: from mail-oi0-f49.google.com ([209.85.218.49]:35496 "EHLO mail-oi0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934590AbbEMTKt (ORCPT ); Wed, 13 May 2015 15:10:49 -0400 MIME-Version: 1.0 In-Reply-To: <20150513125102.GA2628@lukather> References: <1431462804-30467-1-git-send-email-maxime.ripard@free-electrons.com> <20150513112604.GI3066@sirena.org.uk> <20150513125102.GA2628@lukather> Date: Wed, 13 May 2015 21:10:48 +0200 X-Google-Sender-Auth: Qee0s79rfk34YTXEfJmPXvwqmyo Message-ID: Subject: Re: [PATCH] spi: Force the registration of the spidev devices From: Geert Uytterhoeven To: Maxime Ripard Cc: Mark Brown , Greg Kroah-Hartman , "linux-kernel@vger.kernel.org" , Hans de Goede , linux-spi , Martin Sperl , Michal Suchanek 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: 1385 Lines: 34 On Wed, May 13, 2015 at 2:51 PM, Maxime Ripard wrote: >> > This also adds an i2cdev-like feeling, where you get all the >> > spidev devices all the time, without any modification. >> >> I2C is a bit safer here since it's a shared bus so you can't do >> anything to devices not connected to the bus by mistake. > > I'm not sure to understand what you mean here. How is SPI different > from that aspect? If you talk to a nonexistent i2c device, nothing happens, as it just sends a message with a nonexistent address on the shared bus. If you talk to a nonexistent spi device, hell may break loose if e.g. some "smart" hardware engineer used the "unused" CS as a pull-up for the _RESET line on an external device... It's a bit like banging random "unused" GPIOs. 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/