On Sat, 2020-06-27 at 17:40 +0100, Jonathan Cameron wrote:
> On Sun, 21 Jun 2020 15:33:40 +0300
> Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx> wrote:
>
> > There are plenty of bad designs we want to discourage or not have to
> > review
> > manually usually about accessing private (marked as [INTERN]) fields of
> > 'struct iio_dev'.
> >
> > Sometimes users copy drivers that are not always the best examples.
> >
> > A better idea is to hide those fields into the framework.
> > For 'struct iio_dev' this is a 'struct iio_dev_opaque' which wraps a
> > public
> > 'struct iio_dev' object.
> >
> > In the next series, some fields will be moved to this new struct, each
> > with
> > it's own rework.
> >
> > This rework will not be complete-able for a while, as many fields need
> > some
> > drivers to be reworked in order to finalize them (e.g. 'indio_dev-
> > >mlock').
> >
> > But some fields can already be moved, and in time, all of them may get
> > there (in the 'struct iio_dev_opaque' object).
> >
> > Since a lot of drivers also call 'iio_priv()', in order to preserve
> > fast-paths (where this matters), the public iio_dev object will have a
> > 'priv' field that will have the pointer to the private information
> > already
> > computed. The reference returned by this field should be guaranteed to
> > be
> > cacheline aligned.
> >
> > As for the 'iio_priv_to_dev()' helper, this needs to be hidden away.
> > There
> > aren't many users of this helper, and arguably drivers shouldn't need
> > to
> > use it in any fast-paths, as they can maintain a reference to the IIO
> > device.
> Dropped this bit as previous patch deleted iio_priv_to_dev :)
Right.
My bad.
> > The opaque parts will be moved into the 'include/linux/iio/iio-
> > opaque.h'
> > header. Should the hidden information be required for some debugging or
> > some special needs, it can be made available via this header.
> > Otherwise, only the IIO core files should include this file.
> >
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
>
> I've applied this as it stands, but I wonder if we should combine
> this with the existing iio-core.h header.
>
> Can do that later if it makes sense.
Initially, I had thought about putting all of the iio-opaque.h code in iio-
core.h, and limit the include range in drivers/iio, but then thought maybe
leave it in 'include/linux/iio/iio-opaque.h'. That way, it's probably a bit
easier for some debugging.
I am still not sure which direction is best.
But, we can move iio-core.h into iio-opaque.h (or the other way around).
>
> Jonathan
>
>
>
> > ---
> > drivers/iio/industrialio-core.c | 19 +++++++++++++------
> > include/linux/iio/iio-opaque.h | 17 +++++++++++++++++
> > include/linux/iio/iio.h | 6 +++++-
> > 3 files changed, 35 insertions(+), 7 deletions(-)
> > create mode 100644 include/linux/iio/iio-opaque.h
> >
> > diff --git a/drivers/iio/industrialio-core.c
> > b/drivers/iio/industrialio-core.c
> > index 75661661aaba..33e2953cf021 100644
> > --- a/drivers/iio/industrialio-core.c
> > +++ b/drivers/iio/industrialio-core.c
> > @@ -25,6 +25,7 @@
> > #include <linux/debugfs.h>
> > #include <linux/mutex.h>
> > #include <linux/iio/iio.h>
> > +#include <linux/iio/iio-opaque.h>
> > #include "iio_core.h"
> > #include "iio_core_trigger.h"
> > #include <linux/iio/sysfs.h>
> > @@ -1473,6 +1474,8 @@ static void iio_device_unregister_sysfs(struct
> > iio_dev *indio_dev)
> > static void iio_dev_release(struct device *device)
> > {
> > struct iio_dev *indio_dev = dev_to_iio_dev(device);
> > + struct iio_dev_opaque *iio_dev_opaque =
> > to_iio_dev_opaque(indio_dev);
> > +
> > if (indio_dev->modes & INDIO_ALL_TRIGGERED_MODES)
> > iio_device_unregister_trigger_consumer(indio_dev);
> > iio_device_unregister_eventset(indio_dev);
> > @@ -1481,7 +1484,7 @@ static void iio_dev_release(struct device
> > *device)
> > iio_buffer_put(indio_dev->buffer);
> >
> > ida_simple_remove(&iio_ida, indio_dev->id);
> > - kfree(indio_dev);
> > + kfree(iio_dev_opaque);
> > }
> >
> > struct device_type iio_device_type = {
> > @@ -1495,10 +1498,11 @@ struct device_type iio_device_type = {
> > **/
> > struct iio_dev *iio_device_alloc(struct device *parent, int
> > sizeof_priv)
> > {
> > + struct iio_dev_opaque *iio_dev_opaque;
> > struct iio_dev *dev;
> > size_t alloc_size;
> >
> > - alloc_size = sizeof(struct iio_dev);
> > + alloc_size = sizeof(struct iio_dev_opaque);
> > if (sizeof_priv) {
> > alloc_size = ALIGN(alloc_size, IIO_ALIGN);
> > alloc_size += sizeof_priv;
> > @@ -1506,11 +1510,14 @@ struct iio_dev *iio_device_alloc(struct device
> > *parent, int sizeof_priv)
> > /* ensure 32-byte alignment of whole construct ? */
> > alloc_size += IIO_ALIGN - 1;
> >
> > - dev = kzalloc(alloc_size, GFP_KERNEL);
> > - if (!dev)
> > + iio_dev_opaque = kzalloc(alloc_size, GFP_KERNEL);
> > + if (!iio_dev_opaque)
> > return NULL;
> >
> > - dev->dev.parent = parent;
> > + dev = &iio_dev_opaque->indio_dev;
> > + dev->priv = (char *)iio_dev_opaque +
> > + ALIGN(sizeof(struct iio_dev_opaque), IIO_ALIGN);
> > +
> > dev->dev.groups = dev->groups;
> > dev->dev.type = &iio_device_type;
> > dev->dev.bus = &iio_bus_type;
> > @@ -1524,7 +1531,7 @@ struct iio_dev *iio_device_alloc(struct device
> > *parent, int sizeof_priv)
> > if (dev->id < 0) {
> > /* cannot use a dev_err as the name isn't available */
> > pr_err("failed to get device id\n");
> > - kfree(dev);
> > + kfree(iio_dev_opaque);
> > return NULL;
> > }
> > dev_set_name(&dev->dev, "iio:device%d", dev->id);
> > diff --git a/include/linux/iio/iio-opaque.h b/include/linux/iio/iio-
> > opaque.h
> > new file mode 100644
> > index 000000000000..1375674f14cd
> > --- /dev/null
> > +++ b/include/linux/iio/iio-opaque.h
> > @@ -0,0 +1,17 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +
> > +#ifndef _INDUSTRIAL_IO_OPAQUE_H_
> > +#define _INDUSTRIAL_IO_OPAQUE_H_
> > +
> > +/**
> > + * struct iio_dev_opaque - industrial I/O device opaque information
> > + * @indio_dev: public industrial I/O device
> > information
> > + */
> > +struct iio_dev_opaque {
> > + struct iio_dev indio_dev;
> > +};
> > +
> > +#define to_iio_dev_opaque(indio_dev) \
> > + container_of(indio_dev, struct iio_dev_opaque, indio_dev)
> > +
> > +#endif
> > diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> > index 10a6d97a8e3e..86112e35ae5f 100644
> > --- a/include/linux/iio/iio.h
> > +++ b/include/linux/iio/iio.h
> > @@ -522,6 +522,8 @@ struct iio_buffer_setup_ops {
> > * @flags: [INTERN] file ops related flags including busy
> > flag.
> > * @debugfs_dentry: [INTERN] device specific debugfs dentry.
> > * @cached_reg_addr: [INTERN] cached register address for
> > debugfs reads.
> > + * @priv: [DRIVER] reference to driver's private information
> > + * **MUST** be accessed **ONLY** via iio_priv() helper
> > */
> > struct iio_dev {
> > int id;
> > @@ -571,6 +573,7 @@ struct iio_dev {
> > char read_buf[20];
> > unsigned int read_buf_len;
> > #endif
> > + void *priv;
> > };
> >
> > const struct iio_chan_spec
> > @@ -698,9 +701,10 @@ static inline void *iio_device_get_drvdata(const
> > struct iio_dev *indio_dev)
> > #define IIO_ALIGN L1_CACHE_BYTES
> > struct iio_dev *iio_device_alloc(struct device *parent, int
> > sizeof_priv);
> >
> > +/* The information at the returned address is guaranteed to be
> > cacheline aligned */
> > static inline void *iio_priv(const struct iio_dev *indio_dev)
> > {
> > - return (char *)indio_dev + ALIGN(sizeof(struct iio_dev),
> > IIO_ALIGN);
> > + return indio_dev->priv;
> > }
> >
> > void iio_device_free(struct iio_dev *indio_dev);
