On Mon, 2024-06-24 at 18:26 +0200, Olivier MOYSAN wrote: > Hi Nuno, > > On 6/24/24 17:22, Nuno Sá wrote: > > Hi Olivier, > > > > On Mon, 2024-06-24 at 14:43 +0200, Olivier MOYSAN wrote: > > > Hi Jonathan, > > > > > > On 6/23/24 17:11, Jonathan Cameron wrote: > > > > On Tue, 18 Jun 2024 18:08:33 +0200 > > > > Olivier Moysan <olivier.moysan@xxxxxxxxxxx> wrote: > > > > > > > > > Add a generic driver to support sigma delta modulators. > > > > > Typically, this device is a hardware connected to an IIO device > > > > > in charge of the conversion. The device is exposed as an IIO backend > > > > > device. This backend device and the associated conversion device > > > > > can be seen as an aggregate device from IIO framework. > > > > > > > > > > Signed-off-by: Olivier Moysan <olivier.moysan@xxxxxxxxxxx> > > > > > > > > Trivial comments inline. > > > > > > > > > diff --git a/drivers/iio/adc/sd_adc_backend.c > > > > > b/drivers/iio/adc/sd_adc_backend.c > > > > > new file mode 100644 > > > > > index 000000000000..556a49dc537b > > > > > --- /dev/null > > > > > +++ b/drivers/iio/adc/sd_adc_backend.c > > > > > @@ -0,0 +1,110 @@ > > > > > +// SPDX-License-Identifier: GPL-2.0-only > > > > > +/* > > > > > + * Generic sigma delta modulator IIO backend > > > > > + * > > > > > + * Copyright (C) 2024, STMicroelectronics - All Rights Reserved > > > > > + */ > > > > > + > > > > > +#include <linux/iio/backend.h> > > > > > +#include <linux/iio/iio.h> > > > > > +#include <linux/module.h> > > > > > +#include <linux/mod_devicetable.h> > > > > > +#include <linux/platform_device.h> > > > > > +#include <linux/regulator/consumer.h> > > > > > + > > > > > +struct iio_sd_backend_priv { > > > > > + struct regulator *vref; > > > > > + int vref_mv; > > > > > +}; > > > > > + > > > > > +static int sd_backend_enable(struct iio_backend *backend) > > > > > +{ > > > > > + struct iio_sd_backend_priv *priv = > > > > > iio_backend_get_priv(backend); > > > > > + > > > > > + return regulator_enable(priv->vref); > > > > > +}; > > > > > + > > > > > +static void sd_backend_disable(struct iio_backend *backend) > > > > > +{ > > > > > + struct iio_sd_backend_priv *priv = > > > > > iio_backend_get_priv(backend); > > > > > + > > > > > + regulator_disable(priv->vref); > > > > > +}; > > > > > + > > > > > +static int sd_backend_read(struct iio_backend *backend, int *val, int > > > > > *val2, > > > > > long mask) > > > > Nothing to do with this patch as such: > > > > > > > > One day I'm going to bit the bullet and fix that naming. > > > > Long long ago when the Earth was young it actually was a bitmap which > > > > I miscalled a mask - it only had one bit ever set, which was a dumb > > > > bit of API. It's not been true for a long time. > > > > Anyhow, one more instances isn't too much of a problem I guess. > > > > > > > > > > I changed the callback .read_raw to .ext_info_get to take Nuno's comment > > > about iio_backend_read_raw() API, into account. > > > So, I changed this function to > > > static int sd_backend_ext_info_get(struct iio_backend *back, uintptr_t > > > private, const struct iio_chan_spec *chan, char *buf) > > > for v2 version. > > > > > > > Maybe I'm missing something but I think I did not explained myself very > > well. What I > > had in mind was that since you're calling .read_raw() from > > IIO_CHAN_INFO_SCALE and > > IIO_CHAN_INFO_OFFSET, it could make sense to have more dedicated API's. > > Meaning: > > > > iio_backend_read_scale(...) > > iio_backend_read_offset(...) > > > > The iio_backend_read_raw() may make sense when frontends call > > iio_backend_extend_chan_spec() and have no idea what the backend may have > > added to > > the channel. So, in those cases something like this could make sense: > > > > switch (mask) > > IIO_CHAN_INFO_RAW: > > > > ... > > > > default: > > return iio_backend_read_raw(); > > > > but like I said maybe this is me over-complicating and a simple > > iio_backend_read_raw() is sufficient. But I think I never mentioned > > something like > > .read_raw -> .ext_info_get. > > > > Thanks for clarification. Your previous message was actually clear > enough regarding iio_backend_read_raw() API. > > However, your comment about extend_chan_spec(), let me think that I > could maybe spare a new API, and just re-use iio_backend_ext_info_get() > callback. > Nevertheless, this API cannot be used directly, as it can be used only > for a frontend associated to a single backend. There is a comment in > iio_backend_ext_info_get() about the need of another API for such case. > > So I considered introducing this new API (instead of read_raw): > ssize_t iio_backend_ext_info_get_from_backend(struct iio_backend *back, > uintptr_t private, const struct iio_chan_spec *chan, char *buf) > (I'm not sure this name is the most relevant). Yeah, don't think that's the way to go... If you have multiple backends the idea is to add a .get_backend() callback into struct iio_info so we can get the backend handle of the frontend device. It was not done because we still don't have a valid user for such a callback. But having the said the above, I also don't think we should use any extended info API to handle scale and offset as those are standard attributes. That would open a dangerous precedence :). > > But if you don't like this alternative too much, I will keep the initial > "catch all" iio_backend_read_raw() API. Right... - Nuno Sá > > >