linux-kernel - Re: [PATCH 3/4] iio: dac: adi-axi-dac: add data source get

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Message-ID: <7bacip7jwyz7w2fsnnpwbhxg67pwakej46a7bpwxilwkl265d5@jfz7yee7arly>
Date: Mon, 31 Mar 2025 16:40:23 +0200
From: Angelo Dureghello <adureghello@...libre.com>
To: Nuno Sá <noname.nuno@...il.com>
Cc: Nuno Sá <nuno.sa@...log.com>, 
	Jonathan Cameron <jic23@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>, 
	Jonathan Corbet <corbet@....net>, Olivier Moysan <olivier.moysan@...s.st.com>, 
	Michael Hennerich <Michael.Hennerich@...log.com>, linux-iio@...r.kernel.org, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] iio: dac: adi-axi-dac: add data source get

On 28.03.2025 08:15, Nuno Sá wrote:
> On Fri, 2025-03-21 at 21:28 +0100, Angelo Dureghello wrote:
> > From: Angelo Dureghello <adureghello@...libre.com>
> > 
> > Add data source getter.
> > 
> > Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
> > ---
> >  drivers/iio/dac/adi-axi-dac.c | 27 +++++++++++++++++++++++++++
> >  1 file changed, 27 insertions(+)
> > 
> > diff --git a/drivers/iio/dac/adi-axi-dac.c b/drivers/iio/dac/adi-axi-dac.c
> > index
> > 892d770aec69c4259de777058801c9ab33c79923..a6abd828ebdb34800cc08a2151e52a9acda9eba1
> > 100644
> > --- a/drivers/iio/dac/adi-axi-dac.c
> > +++ b/drivers/iio/dac/adi-axi-dac.c
> > @@ -514,6 +514,32 @@ static int axi_dac_data_source_set(struct iio_backend *back,
> > unsigned int chan,
> >  	}
> >  }
> >  
> > +static int axi_dac_data_source_get(struct iio_backend *back, unsigned int chan,
> > +				   enum iio_backend_data_source *data)
> > +{
> > +	struct axi_dac_state *st = iio_backend_get_priv(back);
> > +	int ret;
> > +	u32 val;
> > +
> > +	ret = regmap_read(st->regmap, AXI_DAC_CHAN_CNTRL_7_REG(chan), &val);
> > +	if (ret)
> > +		return ret;
> 
> Is chan something that we can validate? Do we reliable know max number of channels?
>

Ack, will set it to 15, 0 to 15 is what the documentation says.
But at this point should be set in a diffetrent patch for the "set"
too.

Btw, there is something odd here. I tested the generator and it works,
i am enabling RAMP for both channels 0 and 1.
The channel offset here is 0x40, while in ad3552r and generic dac doc
it is 0x58. So, since ramp is working i am supposing the documentation 
can be wrong. 
 
> > +
> > +	switch (val) {
> > +	case AXI_DAC_DATA_INTERNAL_TONE:
> > +		*data = IIO_BACKEND_INTERNAL_CONTINUOUS_WAVE;
> > +		return 0;
> > +	case AXI_DAC_DATA_DMA:
> > +		*data = IIO_BACKEND_EXTERNAL;
> > +		return 0;
> > +	case AXI_DAC_DATA_INTERNAL_RAMP_16BIT:
> > +		*data = IIO_BACKEND_INTERNAL_RAMP_16BIT;
> > +		return 0;
> > +	default:
> > +		return -EINVAL;
> 
> More of a nitpick comment but I would some other error code. This is not really an
> "Invalid argument" situation. Maybe -EIO as the HW is giving something unexpected? or
> ENOTSUPP (likely not exactly like this)...
>
Correct, will set EIO.
 
> - Nuno Sá
> 
> >  	.ddr_disable = axi_dac_ddr_disable,
> >  	.data_stream_enable = axi_dac_data_stream_enable,
> > 
>