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From:   Alexandru Ardelean <ardeleanalex@gmail.com>
Date:   Fri, 5 Feb 2021 10:26:32 +0200
Message-ID: <CA+U=Dsq34ixRT71qD8ZTR7MQ7NDgDZV2EJ+3gT=QQ8wBz4GiGA@mail.gmail.com>
Subject: Re: [PATCH v3 07/11] iio: add reference to iio buffer on iio_dev_attr
To:     Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc:     Alexandru Ardelean <alexandru.ardelean@analog.com>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-iio <linux-iio@vger.kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        "Hennerich, Michael" <Michael.Hennerich@analog.com>,
        Jonathan Cameron <jic23@kernel.org>,
        =?UTF-8?B?TnVubyBTw6E=?= <nuno.sa@analog.com>,
        "Bogdan, Dragos" <dragos.bogdan@analog.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Precedence: bulk

On Thu, Feb 4, 2021 at 8:16 PM Jonathan Cameron
<Jonathan.Cameron@huawei.com> wrote:
>
> On Mon, 1 Feb 2021 16:51:01 +0200
> Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:
>
> > This change adds a reference to a 'struct iio_buffer' object on the
> > iio_dev_attr object. This way, we can use the created iio_dev_attr objects
> > on per-buffer basis (since they're allocated anyway).
> >
> > A minor downside of this change is that the number of parameters on
> > __iio_add_chan_devattr() grows by 1. This looks like it could do with a bit
> > of a re-think.
>
> Could use a bit of macro magic or static inline to keep the old
> version set of parameter and have __iio_add_chan_devattr_with_buf
> or similar.  I'm not sure I'd bother given we don't have that many callers.

If there isn't a strong opinion to add the
__iio_add_chan_devattr_with_buf() version + macro/inline magic, I'd
probably not do it.
In terms of patch-noise, it's not considerably better, and not
necessarily worse.

When I was thinking about the re-think of __iio_add_chan_devattr, I
was thinking of a way to maybe re-architect this.
Maybe, add some {device_}attribute that act as template [at least for
the R/W functions].
This definitely needs some thinking to make it clean and nice.

>
> >
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> > ---
> >  drivers/iio/iio_core.h            | 2 ++
> >  drivers/iio/industrialio-buffer.c | 4 ++++
> >  drivers/iio/industrialio-core.c   | 6 ++++++
> >  drivers/iio/industrialio-event.c  | 1 +
> >  include/linux/iio/sysfs.h         | 3 +++
> >  5 files changed, 16 insertions(+)
> >
> > diff --git a/drivers/iio/iio_core.h b/drivers/iio/iio_core.h
> > index 7d5b179c1fe7..731f5170d5b9 100644
> > --- a/drivers/iio/iio_core.h
> > +++ b/drivers/iio/iio_core.h
> > @@ -12,6 +12,7 @@
> >  #include <linux/kernel.h>
> >  #include <linux/device.h>
> >
> > +struct iio_buffer;
> >  struct iio_chan_spec;
> >  struct iio_dev;
> >
> > @@ -43,6 +44,7 @@ int __iio_add_chan_devattr(const char *postfix,
> >                          u64 mask,
> >                          enum iio_shared_by shared_by,
> >                          struct device *dev,
> > +                        struct iio_buffer *buffer,
> >                          struct list_head *attr_list);
> >  void iio_free_chan_devattr_list(struct list_head *attr_list);
> >
> > diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> > index f82decf92b7c..a525e88b302f 100644
> > --- a/drivers/iio/industrialio-buffer.c
> > +++ b/drivers/iio/industrialio-buffer.c
>
> > @@ -447,6 +447,7 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
> >                                    0,
> >                                    IIO_SEPARATE,
> >                                    &indio_dev->dev,
> > +                                  buffer,
> >                                    &buffer->scan_el_dev_attr_list);
> >       if (ret)
> >               return ret;
> > @@ -458,6 +459,7 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
> >                                    0,
> >                                    0,
> >                                    &indio_dev->dev,
> > +                                  buffer,
> >                                    &buffer->scan_el_dev_attr_list);
> >       if (ret)
> >               return ret;
> > @@ -470,6 +472,7 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
> >                                            chan->scan_index,
> >                                            0,
> >                                            &indio_dev->dev,
> > +                                          buffer,
> >                                            &buffer->scan_el_dev_attr_list);
> >       else
> >               ret = __iio_add_chan_devattr("en",
> > @@ -479,6 +482,7 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
> >                                            chan->scan_index,
> >                                            0,
> >                                            &indio_dev->dev,
> > +                                          buffer,
> >                                            &buffer->scan_el_dev_attr_list);
> >       if (ret)
> >               return ret;
> > diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> > index ccd7aaff6d13..c68130885d83 100644
> > --- a/drivers/iio/industrialio-core.c
> > +++ b/drivers/iio/industrialio-core.c
> > @@ -1114,6 +1114,7 @@ int __iio_add_chan_devattr(const char *postfix,
> >                          u64 mask,
> >                          enum iio_shared_by shared_by,
> >                          struct device *dev,
> > +                        struct iio_buffer *buffer,
> >                          struct list_head *attr_list)
> >  {
> >       int ret;
> > @@ -1129,6 +1130,7 @@ int __iio_add_chan_devattr(const char *postfix,
> >               goto error_iio_dev_attr_free;
> >       iio_attr->c = chan;
> >       iio_attr->address = mask;
> > +     iio_attr->buffer = buffer;
> >       list_for_each_entry(t, attr_list, l)
> >               if (strcmp(t->dev_attr.attr.name,
> >                          iio_attr->dev_attr.attr.name) == 0) {
> > @@ -1165,6 +1167,7 @@ static int iio_device_add_channel_label(struct iio_dev *indio_dev,
> >                                    0,
> >                                    IIO_SEPARATE,
> >                                    &indio_dev->dev,
> > +                                  NULL,
> >                                    &iio_dev_opaque->channel_attr_list);
> >       if (ret < 0)
> >               return ret;
> > @@ -1190,6 +1193,7 @@ static int iio_device_add_info_mask_type(struct iio_dev *indio_dev,
> >                                            i,
> >                                            shared_by,
> >                                            &indio_dev->dev,
> > +                                          NULL,
> >                                            &iio_dev_opaque->channel_attr_list);
> >               if ((ret == -EBUSY) && (shared_by != IIO_SEPARATE))
> >                       continue;
> > @@ -1226,6 +1230,7 @@ static int iio_device_add_info_mask_type_avail(struct iio_dev *indio_dev,
> >                                            i,
> >                                            shared_by,
> >                                            &indio_dev->dev,
> > +                                          NULL,
> >                                            &iio_dev_opaque->channel_attr_list);
> >               kfree(avail_postfix);
> >               if ((ret == -EBUSY) && (shared_by != IIO_SEPARATE))
> > @@ -1322,6 +1327,7 @@ static int iio_device_add_channel_sysfs(struct iio_dev *indio_dev,
> >                                       i,
> >                                       ext_info->shared,
> >                                       &indio_dev->dev,
> > +                                     NULL,
> >                                       &iio_dev_opaque->channel_attr_list);
> >                       i++;
> >                       if (ret == -EBUSY && ext_info->shared)
> > diff --git a/drivers/iio/industrialio-event.c b/drivers/iio/industrialio-event.c
> > index ea8947cc21e4..a30e289fc362 100644
> > --- a/drivers/iio/industrialio-event.c
> > +++ b/drivers/iio/industrialio-event.c
> > @@ -385,6 +385,7 @@ static int iio_device_add_event(struct iio_dev *indio_dev,
> >
> >               ret = __iio_add_chan_devattr(postfix, chan, show, store,
> >                        (i << 16) | spec_index, shared_by, &indio_dev->dev,
> > +                      NULL,
> >                       &iio_dev_opaque->event_interface->dev_attr_list);
> >               kfree(postfix);
> >
> > diff --git a/include/linux/iio/sysfs.h b/include/linux/iio/sysfs.h
> > index b532c875bc24..e51fba66de4b 100644
> > --- a/include/linux/iio/sysfs.h
> > +++ b/include/linux/iio/sysfs.h
> > @@ -9,6 +9,7 @@
> >  #ifndef _INDUSTRIAL_IO_SYSFS_H_
> >  #define _INDUSTRIAL_IO_SYSFS_H_
> >
> > +struct iio_buffer;
> >  struct iio_chan_spec;
> >
> >  /**
> > @@ -17,12 +18,14 @@ struct iio_chan_spec;
> >   * @address: associated register address
> >   * @l:               list head for maintaining list of dynamically created attrs
> >   * @c:               specification for the underlying channel
> > + * @buffer:  the IIO buffer to which this attribute belongs to (if any)
> >   */
> >  struct iio_dev_attr {
> >       struct device_attribute dev_attr;
> >       u64 address;
> >       struct list_head l;
> >       struct iio_chan_spec const *c;
> > +     struct iio_buffer *buffer;
> >  };
> >
> >  #define to_iio_dev_attr(_dev_attr)                           \
>