Re: [PATCH v3 1/5] iio: core: register buffer fileops only if buffer present

["Ardelean, Alexandru" <alexandru.Ardelean@analog.com>]

On Tue, 2020-04-14 at 05:20 +0000, Ardelean, Alexandru wrote:
> [External]
> 
> On Mon, 2020-04-13 at 16:47 +0100, Jonathan Cameron wrote:
> > [External]
> > 
> > On Fri, 10 Apr 2020 17:17:25 +0300
> > Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:
> > 
> > > The intent is to localize all buffer ops into the industrialio-buffer.c
> > > file, to be able to add support for multiple buffers per IIO device.
> > > 
> > > We still need to allocate a chardev in __iio_device_register() to be able
> > > to pass event ioctl commands. So, if the IIO device has no buffer, we
> > > create the legacy chardev for the event ioctl() command.
> > > 
> > > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> > 
> > Whilst we are here, can we avoid allocating the chardev at all if
> > we have neither buffer support, nor events?  So don't add the chrdev to the
> > device.
> 
> That should happen after patch 5/5.
> If there aren't any buffers, and 'indio_dev->event_interface' is NULL, no
> chardev should exist.
> 
> Maybe I can reduce this, given the fact that this goes away into files later.
> I did things in very-small incremental steps that I later squashed.
> 
> This patch kind of highlights an intermediate step towards the final rework
> [moving chardevs into files]

oh...
silly me
we can check if 'indio_dev->event_interface' is NULL here as well


> 
> > That covers quite a wide range of slow devices and is a nice incidental
> > improvement (to be honest I'd forgotten we actually created a chardev
> > in those circumstance :(
> > 
> > Jonathan
> > 
> > > ---
> > >  drivers/iio/industrialio-core.c | 14 +++++++++++++-
> > >  1 file changed, 13 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-
> > > core.c
> > > index 157d95a24faa..c8c074602709 100644
> > > --- a/drivers/iio/industrialio-core.c
> > > +++ b/drivers/iio/industrialio-core.c
> > > @@ -1707,6 +1707,15 @@ static int iio_check_unique_scan_index(struct
> > > iio_dev
> > > *indio_dev)
> > >  
> > >  static const struct iio_buffer_setup_ops noop_ring_setup_ops;
> > >  
> > > +static const struct file_operations iio_event_fileops = {
> > > +	.release = iio_chrdev_release,
> > > +	.open = iio_chrdev_open,
> > > +	.owner = THIS_MODULE,
> > > +	.llseek = noop_llseek,
> > > +	.unlocked_ioctl = iio_ioctl,
> > > +	.compat_ioctl = compat_ptr_ioctl,
> > > +};
> > > +
> > >  int __iio_device_register(struct iio_dev *indio_dev, struct module
> > > *this_mod)
> > >  {
> > >  	int ret;
> > > @@ -1757,7 +1766,10 @@ int __iio_device_register(struct iio_dev
> > > *indio_dev,
> > > struct module *this_mod)
> > >  		indio_dev->setup_ops == NULL)
> > >  		indio_dev->setup_ops = &noop_ring_setup_ops;
> > >  
> > > -	cdev_init(&indio_dev->chrdev, &iio_buffer_fileops);
> > > +	if (indio_dev->buffer)
> > > +		cdev_init(&indio_dev->chrdev, &iio_buffer_fileops);
> > > +	else
> > > +		cdev_init(&indio_dev->chrdev, &iio_event_fileops);
> > >  
> > >  	indio_dev->chrdev.owner = this_mod;
> > >