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From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Jonathan Cameron <jic23@kernel.org>
Cc: Eugen Hristev <eugen.hristev@microchip.com>,
	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
Subject: Re: [PATCH v3 06/11] iio: inkern: add module put/get on iio dev module when requesting channels
Date: Mon, 16 Apr 2018 16:58:21 -0700	[thread overview]
Message-ID: <20180416235821.GF77055@dtor-ws> (raw)
In-Reply-To: <20180415203321.1aaaf91e@archlinux>

On Sun, Apr 15, 2018 at 08:33:21PM +0100, Jonathan Cameron wrote:
> On Tue, 10 Apr 2018 11:57:52 +0300
> Eugen Hristev <eugen.hristev@microchip.com> 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 <eugen.hristev@microchip.com>
> > ---
> >  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 <linux/slab.h>
> >  #include <linux/mutex.h>
> >  #include <linux/of.h>
> > +#include <linux/module.h>
> >  
> >  #include <linux/iio/iio.h>
> >  #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.

-- 
Dmitry

  reply	other threads:[~2018-04-16 23:58 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-10  8:57 [PATCH v3 00/11] Add support for SAMA5D2 touchscreen Eugen Hristev
2018-04-10  8:57 ` [PATCH v3 01/11] iio: adc: at91-sama5d2_adc: fix channel configuration for differential channels Eugen Hristev
2018-04-15 19:23   ` Jonathan Cameron
2018-04-10  8:57 ` [PATCH v3 02/11] MAINTAINERS: add generic resistive touchscreen adc Eugen Hristev
2018-04-10  8:57 ` [PATCH v3 03/11] iio: Add channel for Position Relative Eugen Hristev
2018-04-15 19:29   ` Jonathan Cameron
2018-04-17  7:30     ` Eugen Hristev
2018-04-18  9:32       ` Jonathan Cameron
2018-04-10  8:57 ` [PATCH v3 04/11] dt-bindings: input: touchscreen: add pressure threshold touchscreen property Eugen Hristev
2018-04-13 18:33   ` Rob Herring
2018-04-10  8:57 ` [PATCH v3 05/11] dt-bindings: input: touchscreen: resistive-adc-touch: create bindings Eugen Hristev
2018-04-13 18:34   ` Rob Herring
2018-04-10  8:57 ` [PATCH v3 06/11] iio: inkern: add module put/get on iio dev module when requesting channels Eugen Hristev
2018-04-15 19:33   ` Jonathan Cameron
2018-04-16 23:58     ` Dmitry Torokhov [this message]
2018-04-17  7:39       ` Eugen Hristev
2018-04-17 19:19         ` Dmitry Torokhov
2018-04-18  9:35           ` Jonathan Cameron
2018-04-18 12:37             ` Lars-Peter Clausen
2018-04-10  8:57 ` [PATCH v3 07/11] iio: adc: at91-sama5d2_adc: add support for position and pressure channels Eugen Hristev
2018-04-15 19:45   ` Jonathan Cameron
2018-04-10  8:57 ` [PATCH v3 08/11] input: touchscreen: resistive-adc-touch: add generic resistive ADC touchscreen Eugen Hristev
2018-04-23 23:22   ` Dmitry Torokhov
2018-04-23 23:24     ` Dmitry Torokhov
2018-04-10  8:57 ` [PATCH v3 09/11] dt-bindings: iio: adc: at91-sama5d2_adc: add channel specific consumer info Eugen Hristev
2018-04-10  8:57 ` [PATCH v3 10/11] ARM: dts: at91: sama5d2: add channel cells for ADC device Eugen Hristev
2018-04-10  8:57 ` [PATCH v3 11/11] ARM: dts: at91: sama5d2: Add resistive touch device Eugen Hristev

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