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 <eugen.hristev@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
---
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.
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
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