From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out-098.synserver.de ([212.40.185.98]:1038 "EHLO smtp-out-098.synserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757721AbbAIQRA (ORCPT ); Fri, 9 Jan 2015 11:17:00 -0500 Message-ID: <54AFFEF9.5080408@metafoo.de> Date: Fri, 09 Jan 2015 17:16:57 +0100 From: Lars-Peter Clausen MIME-Version: 1.0 To: "Ivan T. Ivanov" CC: Jonathan Cameron , Hartmut Knaack , Peter Meerwald , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] iio: Simplify IIO provider access locking mechanism References: <1420817893-5858-1-git-send-email-iivanov@mm-sol.com> <54AFF6C4.9020306@metafoo.de> <1420818639.28652.5.camel@mm-sol.com> <54AFF9D3.7000007@metafoo.de> <1420820083.28652.7.camel@mm-sol.com> In-Reply-To: <1420820083.28652.7.camel@mm-sol.com> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 01/09/2015 05:14 PM, Ivan T. Ivanov wrote: > > On Fri, 2015-01-09 at 16:54 +0100, Lars-Peter Clausen wrote: >> On 01/09/2015 04:50 PM, Ivan T. Ivanov wrote: >>> On Fri, 2015-01-09 at 16:41 +0100, Lars-Peter Clausen wrote: >>>> On 01/09/2015 04:38 PM, Ivan T. Ivanov wrote: >>>>> Instead of checking whether provider module is still >>>>> loaded on every access to device just lock module to >>>>> memory when client get reference to provider device. >>>>> >>>> >>>> This has nothing to do with the module, it's about the device. In the Linux >>>> device driver model as device can be unbound at any time and the IIO >>>> framework needs to handle this. >>>> >>> >>> Hm. Probably i am missing something here, but is this >>> still true if we have reference to device structure? >> >> Yes, that only prevents the memory of device from being freed. But the >> device can still be unbound from the driver. >> >> Think of e.g. a USB device that is pulled from the USB connector. Nothing >> you can do in software about having the device disappear. >> > > Agree, but I think that the patch is still valid. Module > have to be pinned in memory as long as there are device > driver users. No, the idea of the Linux driver model is that you can remove the module of a driver at any time, which will unbind the device from the driver. Once you reinsert the module the device will be re-bound to the driver. - Lars