[IIO] Help understanding iio_priv(..)

[IIO] Help understanding iio_priv(..)

[Aishwarya Pant]

Hi

I have been looking at the IIO task and came across this function
iio_priv(..). It is defined as-


static inline void *iio_priv(const struct iio_dev *indio_dev)
{
        return (char *)indio_dev + ALIGN(sizeof(struct iio_dev),
	IIO_ALIGN);
}

It returns a void pointer and used as struct dev_state = iio_priv(indio_dev).
Looks like it is used to store an iio device state private to the file.

Could someone help me understand what exactly is happening inside here?

Thanks
Aishwarya

Re: [Outreachy kernel] [IIO] Help understanding iio_priv(..)

[Julia Lawall]

On Tue, 14 Mar 2017, Aishwarya Pant wrote:

> Hi
>
> I have been looking at the IIO task and came across this function
> iio_priv(..). It is defined as-
>
>
> static inline void *iio_priv(const struct iio_dev *indio_dev)
> {
>         return (char *)indio_dev + ALIGN(sizeof(struct iio_dev),
> 	IIO_ALIGN);
> }
>
> It returns a void pointer and used as struct dev_state = iio_priv(indio_dev).
> Looks like it is used to store an iio device state private to the file.
>
> Could someone help me understand what exactly is happening inside here?

Probably it would help to look at how the priv pointer is initialized.

julia

>
> Thanks
> Aishwarya
>
>
>
> --
> You received this message because you are subscribed to the Google Groups "outreachy-kernel" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to outreachy-kernel+unsubscribe@googlegroups.com.
> To post to this group, send email to outreachy-kernel@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/outreachy-kernel/20170313201511.GA12957%40aishwarya.
> For more options, visit https://groups.google.com/d/optout.
>

Re: [Outreachy kernel] [IIO] Help understanding iio_priv(..)

[Aishwarya Pant]

On Tue, Mar 14, 2017 at 01:43:08PM +0100, Julia Lawall wrote:
> 
> 
> On Tue, 14 Mar 2017, Aishwarya Pant wrote:
> 
> > Hi
> >
> > I have been looking at the IIO task and came across this function
> > iio_priv(..). It is defined as-
> >
> >
> > static inline void *iio_priv(const struct iio_dev *indio_dev)
> > {
> >         return (char *)indio_dev + ALIGN(sizeof(struct iio_dev),
> > 	IIO_ALIGN);
> > }
> >
> > It returns a void pointer and used as struct dev_state = iio_priv(indio_dev).
> > Looks like it is used to store an iio device state private to the file.
> >
> > Could someone help me understand what exactly is happening inside here?
> 
> Probably it would help to look at how the priv pointer is initialized.

Looking at how iio_dev is defined helped :)

struct iio_dev indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*chip))

> 
> julia
> 
> >
> > Thanks
> > Aishwarya
> >
> >
> >
> > --
> > You received this message because you are subscribed to the Google Groups "outreachy-kernel" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to outreachy-kernel+unsubscribe@googlegroups.com.
> > To post to this group, send email to outreachy-kernel@googlegroups.com.
> > To view this discussion on the web visit https://groups.google.com/d/msgid/outreachy-kernel/20170313201511.GA12957%40aishwarya.
> > For more options, visit https://groups.google.com/d/optout.
> >