linux-kernel - Re: [RFC PATCH 00/12] iio: core,buffer: add support for multiple IIO buffers per IIO device

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Message-ID: <CA+U=DspcRkY9-RfAvR9wRwbo_zpy87APb6gxnBWjLHRMZesj9A@mail.gmail.com>
Date:   Mon, 23 Nov 2020 15:03:16 +0200
From:   Alexandru Ardelean <ardeleanalex@...il.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Alexandru Ardelean <alexandru.ardelean@...log.com>,
        linux-iio <linux-iio@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Lars-Peter Clausen <lars@...afoo.de>
Subject: Re: [RFC PATCH 00/12] iio: core,buffer: add support for multiple IIO
 buffers per IIO device

On Sat, Nov 21, 2020 at 8:53 PM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Tue, 17 Nov 2020 18:23:28 +0200
> Alexandru Ardelean <alexandru.ardelean@...log.com> wrote:
>
> > Continuing from:
> >   https://lore.kernel.org/linux-iio/20200517144023.6c5cb169@archlinux/
> >
> > This is a V2 of the initial attempt in the discussion above.
> > But it did not occur to me that I should mark it as V2 when I generated
> > the patches.
> > I've only tested [so far] that the current IIO buffer mechnism still works.
> > And decided to show this sketch patchset.
> >
> > This requires the ioctl() centralization mechanism, for which I sent a
> > fix earlier.
> >   https://lore.kernel.org/linux-iio/CA+U=Dsqf3UgyM666Gg9EmehpWiucDx2P0bmsC9JR--JJDT_eWQ@mail.gmail.com/T/#t
> >   https://lore.kernel.org/linux-iio/20201117095154.7189-1-alexandru.ardelean@analog.com/T/#u
> >
> > The gist of this is that now, the first IIO buffer should work as
> > before, but all extra buffers should go through the anon inodes
> > mechanism.
> > I'd need to find a device or a way or a chip to test these extra buffers
> > stuff. But I'm confident that this current form should eventually work
> > with multiple IIO buffers per 1 IIO device and with anon inodes.
> >
> > Maybe I'll take some of the patches in this set separately and send them
> > individually. The problem with patchsets like this that tackle changes
> > in a framework (like IIO) is that I become unsure after the 5th-7th patch,
> > that the approach is correct. And I get even more unsure after that.
> >
> > I'll create some userspace code to test this a bit, but I thought I'd
> > send an RFC in the meantime.
>
> From a first read, with all the warnings you give above, this looks pretty
> good to me.   The kobj stuff is a little nasty and needs more docs
> but other than that it all looks quite pleasant and readable and was
> roughly what I was expecting from earlier discussions (which is great!).
>
> Good work on this, looking forward to next steps.

Thanks.
I'll see about re-spinning this.
With the iio_buffer_set_attrs() change merged, this  patchset has a
new context that I need to take a look at.

>
> Jonathan
>
> >
> > Alexandru Ardelean (12):
> >   iio: core: register chardev only if needed
> >   iio: buffer: add back-ref from iio_buffer to iio_dev
> >   iio: buffer: rework buffer & scan_elements dir creation
> >   iio: buffer: add index to the first IIO buffer dir and symlink it back
> >   iio: core: split __iio_device_attr_init() to init only the attr object
> >   iio: buffer: re-route scan_elements via it's kobj_type
> >   iio: buffer: re-route core buffer attributes via it's new kobj_type
> >   iio: buffer: add helper to get the IIO device to which a buffer
> >     belongs
> >   iio: re-route all buffer attributes through new buffer kobj_type
> >   iio: core: wrap iio device & buffer into struct for character devices
> >   iio: buffer: introduce support for attaching more IIO buffers
> >   iio: buffer: add ioctl() to support opening extra buffers for IIO
> >     device
> >
> >  drivers/iio/accel/adxl372.c                   |  36 +-
> >  drivers/iio/accel/bmc150-accel-core.c         |  34 +-
> >  drivers/iio/adc/at91-sama5d2_adc.c            |  30 +-
> >  .../buffer/industrialio-buffer-dmaengine.c    |  13 +-
> >  .../cros_ec_sensors/cros_ec_sensors_core.c    |  30 +-
> >  .../common/hid-sensors/hid-sensor-trigger.c   |  32 +-
> >  drivers/iio/iio_core.h                        |  11 +
> >  drivers/iio/industrialio-buffer.c             | 582 ++++++++++++++----
> >  drivers/iio/industrialio-core.c               | 117 ++--
> >  include/linux/iio/buffer.h                    |   2 +
> >  include/linux/iio/buffer_impl.h               |  25 +-
> >  include/linux/iio/iio-opaque.h                |   6 +
> >  include/linux/iio/iio.h                       |   2 +-
> >  include/linux/iio/sysfs.h                     |  50 ++
> >  include/uapi/linux/iio/buffer.h               |  16 +
> >  15 files changed, 735 insertions(+), 251 deletions(-)
> >  create mode 100644 include/uapi/linux/iio/buffer.h
> >
>