From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752027AbeDQHmF (ORCPT ); Tue, 17 Apr 2018 03:42:05 -0400 Received: from esa3.microchip.iphmx.com ([68.232.153.233]:27197 "EHLO esa3.microchip.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751057AbeDQHmC (ORCPT ); Tue, 17 Apr 2018 03:42:02 -0400 X-IronPort-AV: E=Sophos;i="5.48,462,1517900400"; d="scan'208";a="13311792" Subject: Re: [PATCH v3 06/11] iio: inkern: add module put/get on iio dev module when requesting channels To: Dmitry Torokhov , Jonathan Cameron CC: , , , , , , , , References: <1523350677-27106-1-git-send-email-eugen.hristev@microchip.com> <1523350677-27106-7-git-send-email-eugen.hristev@microchip.com> <20180415203321.1aaaf91e@archlinux> <20180416235821.GF77055@dtor-ws> From: Eugen Hristev Message-ID: <67771f4c-d30c-4a28-2a9b-d5585186d60a@microchip.com> Date: Tue, 17 Apr 2018 10:39:24 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180416235821.GF77055@dtor-ws> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17.04.2018 02:58, Dmitry Torokhov wrote: > On Sun, Apr 15, 2018 at 08:33:21PM +0100, Jonathan Cameron wrote: >> On Tue, 10 Apr 2018 11:57:52 +0300 >> Eugen Hristev wrote: >> >>> When requesting channels for a particular consumer device, >>> besides requesting the device (incrementing the reference counter), also >>> do it for the driver module of the iio dev. This will avoid the situation >>> where the producer IIO device can be removed and the consumer is still >>> present in the kernel. >>> >>> Signed-off-by: Eugen Hristev >>> --- >>> drivers/iio/inkern.c | 8 +++++++- >>> 1 file changed, 7 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c >>> index ec98790..68d9b87 100644 >>> --- a/drivers/iio/inkern.c >>> +++ b/drivers/iio/inkern.c >>> @@ -11,6 +11,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> >>> #include >>> #include "iio_core.h" >>> @@ -152,6 +153,7 @@ static int __of_iio_channel_get(struct iio_channel *channel, >>> if (index < 0) >>> goto err_put; >>> channel->channel = &indio_dev->channels[index]; >>> + try_module_get(channel->indio_dev->driver_module); >> >> And if it fails? (the module we are trying to get is going away...) >> >> We should try and handle it I think. Be it by just erroring out of here. > > Even more, this has nothing to do with modules. A device can go away for > any number of reasons (we unbind it manually via sysfs, we pull the USB > plug from the host in case it is USB-connected device, we unload I2C > adapter for the bus device resides on, we kick underlying PCI device) > and we should be able to handle this in some fashion. Handling errors > from reads and ignoring garbage is one of methods. > > FWIW this is a NACK from me. > > Thanks. Hello, This patch is actually a "best effort attempt" for the consumer driver (touch driver) to get a reference to the producer of the data (the IIO device), when it requests the specific channels. As of this moment, there is no attempt whatsoever for the consumer to have a reference on the producer driver. Thus, the producer can be removed at any time, and the consumer will fail ungraciously. I can change the perspective from "best effort" to "mandatory" to get a reference to the producer, or you wish to stop trying to get any reference at all (remove this patch completely) ? Thanks, Eugen > From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eugen Hristev Subject: Re: [PATCH v3 06/11] iio: inkern: add module put/get on iio dev module when requesting channels Date: Tue, 17 Apr 2018 10:39:24 +0300 Message-ID: <67771f4c-d30c-4a28-2a9b-d5585186d60a@microchip.com> References: <1523350677-27106-1-git-send-email-eugen.hristev@microchip.com> <1523350677-27106-7-git-send-email-eugen.hristev@microchip.com> <20180415203321.1aaaf91e@archlinux> <20180416235821.GF77055@dtor-ws> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180416235821.GF77055@dtor-ws> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Dmitry Torokhov , Jonathan Cameron Cc: ludovic.desroches@microchip.com, alexandre.belloni@bootlin.com, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org, linux-input@vger.kernel.org, nicolas.ferre@microchip.com, robh@kernel.org List-Id: devicetree@vger.kernel.org On 17.04.2018 02:58, Dmitry Torokhov wrote: > On Sun, Apr 15, 2018 at 08:33:21PM +0100, Jonathan Cameron wrote: >> On Tue, 10 Apr 2018 11:57:52 +0300 >> Eugen Hristev wrote: >> >>> When requesting channels for a particular consumer device, >>> besides requesting the device (incrementing the reference counter), also >>> do it for the driver module of the iio dev. This will avoid the situation >>> where the producer IIO device can be removed and the consumer is still >>> present in the kernel. >>> >>> Signed-off-by: Eugen Hristev >>> --- >>> drivers/iio/inkern.c | 8 +++++++- >>> 1 file changed, 7 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c >>> index ec98790..68d9b87 100644 >>> --- a/drivers/iio/inkern.c >>> +++ b/drivers/iio/inkern.c >>> @@ -11,6 +11,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> >>> #include >>> #include "iio_core.h" >>> @@ -152,6 +153,7 @@ static int __of_iio_channel_get(struct iio_channel *channel, >>> if (index < 0) >>> goto err_put; >>> channel->channel = &indio_dev->channels[index]; >>> + try_module_get(channel->indio_dev->driver_module); >> >> And if it fails? (the module we are trying to get is going away...) >> >> We should try and handle it I think. Be it by just erroring out of here. > > Even more, this has nothing to do with modules. A device can go away for > any number of reasons (we unbind it manually via sysfs, we pull the USB > plug from the host in case it is USB-connected device, we unload I2C > adapter for the bus device resides on, we kick underlying PCI device) > and we should be able to handle this in some fashion. Handling errors > from reads and ignoring garbage is one of methods. > > FWIW this is a NACK from me. > > Thanks. Hello, This patch is actually a "best effort attempt" for the consumer driver (touch driver) to get a reference to the producer of the data (the IIO device), when it requests the specific channels. As of this moment, there is no attempt whatsoever for the consumer to have a reference on the producer driver. Thus, the producer can be removed at any time, and the consumer will fail ungraciously. I can change the perspective from "best effort" to "mandatory" to get a reference to the producer, or you wish to stop trying to get any reference at all (remove this patch completely) ? Thanks, Eugen > From mboxrd@z Thu Jan 1 00:00:00 1970 From: eugen.hristev@microchip.com (Eugen Hristev) Date: Tue, 17 Apr 2018 10:39:24 +0300 Subject: [PATCH v3 06/11] iio: inkern: add module put/get on iio dev module when requesting channels In-Reply-To: <20180416235821.GF77055@dtor-ws> References: <1523350677-27106-1-git-send-email-eugen.hristev@microchip.com> <1523350677-27106-7-git-send-email-eugen.hristev@microchip.com> <20180415203321.1aaaf91e@archlinux> <20180416235821.GF77055@dtor-ws> Message-ID: <67771f4c-d30c-4a28-2a9b-d5585186d60a@microchip.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 17.04.2018 02:58, Dmitry Torokhov wrote: > On Sun, Apr 15, 2018 at 08:33:21PM +0100, Jonathan Cameron wrote: >> On Tue, 10 Apr 2018 11:57:52 +0300 >> Eugen Hristev wrote: >> >>> When requesting channels for a particular consumer device, >>> besides requesting the device (incrementing the reference counter), also >>> do it for the driver module of the iio dev. This will avoid the situation >>> where the producer IIO device can be removed and the consumer is still >>> present in the kernel. >>> >>> Signed-off-by: Eugen Hristev >>> --- >>> drivers/iio/inkern.c | 8 +++++++- >>> 1 file changed, 7 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c >>> index ec98790..68d9b87 100644 >>> --- a/drivers/iio/inkern.c >>> +++ b/drivers/iio/inkern.c >>> @@ -11,6 +11,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> >>> #include >>> #include "iio_core.h" >>> @@ -152,6 +153,7 @@ static int __of_iio_channel_get(struct iio_channel *channel, >>> if (index < 0) >>> goto err_put; >>> channel->channel = &indio_dev->channels[index]; >>> + try_module_get(channel->indio_dev->driver_module); >> >> And if it fails? (the module we are trying to get is going away...) >> >> We should try and handle it I think. Be it by just erroring out of here. > > Even more, this has nothing to do with modules. A device can go away for > any number of reasons (we unbind it manually via sysfs, we pull the USB > plug from the host in case it is USB-connected device, we unload I2C > adapter for the bus device resides on, we kick underlying PCI device) > and we should be able to handle this in some fashion. Handling errors > from reads and ignoring garbage is one of methods. > > FWIW this is a NACK from me. > > Thanks. Hello, This patch is actually a "best effort attempt" for the consumer driver (touch driver) to get a reference to the producer of the data (the IIO device), when it requests the specific channels. As of this moment, there is no attempt whatsoever for the consumer to have a reference on the producer driver. Thus, the producer can be removed at any time, and the consumer will fail ungraciously. I can change the perspective from "best effort" to "mandatory" to get a reference to the producer, or you wish to stop trying to get any reference at all (remove this patch completely) ? Thanks, Eugen >