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SubjectRe: [PATCH v3 06/11] iio: inkern: add module put/get on iio dev module when requesting channels
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.


>
> return 0;
>
> @@ -256,8 +258,10 @@ static struct iio_channel *of_iio_channel_get_all(struct device *dev)
> return chans;
>
> error_free_chans:
> - for (i = 0; i < mapind; i++)
> + for (i = 0; i < mapind; i++) {
> + module_put(chans[i].indio_dev->driver_module);
> iio_device_put(chans[i].indio_dev);
> + }
> kfree(chans);
> return ERR_PTR(ret);
> }
> @@ -351,6 +355,7 @@ void iio_channel_release(struct iio_channel *channel)
> {
> if (!channel)
> return;
> + module_put(channel->indio_dev->driver_module);
> iio_device_put(channel->indio_dev);
> kfree(channel);
> }
> @@ -482,6 +487,7 @@ void iio_channel_release_all(struct iio_channel *channels)
> struct iio_channel *chan = &channels[0];
>
> while (chan->indio_dev) {
> + module_put(chan->indio_dev->driver_module);
> iio_device_put(chan->indio_dev);
> chan++;
> }

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