Re: [PATCH v5 7/8] iio: adc: ad9467: convert to backend framework

["Nuno Sá" <noname.nuno@gmail.com>]

On Fri, 2024-01-12 at 17:33 +0000, Jonathan Cameron wrote:
> On Fri, 12 Jan 2024 17:40:21 +0100
> Nuno Sa via B4 Relay <devnull+nuno.sa.analog.com@kernel.org> wrote:
> 
> > From: Nuno Sa <nuno.sa@analog.com>
> > 
> > Convert the driver to use the new IIO backend framework. The device
> > functionality is expected to be the same (meaning no added or removed
> > features).
> > 
> > Also note this patch effectively breaks ABI and that's needed so we can
> > properly support this device and add needed features making use of the
> > new IIO framework.
> > 
> > Signed-off-by: Nuno Sa <nuno.sa@analog.com>
> 
> Hi Nuno,
> 
> Some trivial stuff in here (not I reviewed in reverse so might make more
> sense read that way).  Mostly little changes that will reduce what
> appears to be going on in this patch to the minimum possible
> 
> 
> > +
> >  static int ad9467_outputmode_set(struct spi_device *spi, unsigned int mode)
> >  {
> >  	int ret;
> > @@ -401,19 +419,17 @@ static int ad9467_outputmode_set(struct spi_device
> > *spi, unsigned int mode)
> >  				AN877_ADC_TRANSFER_SYNC);
> >  }
> >  
> > -static int ad9467_scale_fill(struct adi_axi_adc_conv *conv)
> > +static int ad9467_scale_fill(struct ad9467_state *st)
> >  {
> > -	const struct adi_axi_adc_chip_info *info = conv->chip_info;
> > -	struct ad9467_state *st = adi_axi_adc_conv_priv(conv);
> >  	unsigned int i, val1, val2;
> 	const struct adi_axi_adc_chip_info *info = st->info;
> I think...
> 
> Makes this patch more minimal which is nice and it's not a bad change
> in it's own right..
> 
> Same with some other cases changed by this patch.

Alright, will do it in all the places you pointed out...

> 
> >  
> > -	st->scales = devm_kmalloc_array(&st->spi->dev, info->num_scales,
> > +	st->scales = devm_kmalloc_array(&st->spi->dev, st->info-
> > >num_scales,
> >  					sizeof(*st->scales), GFP_KERNEL);
> >  	if (!st->scales)
> >  		return -ENOMEM;
> >  
> > -	for (i = 0; i < info->num_scales; i++) {
> > -		__ad9467_get_scale(conv, i, &val1, &val2);
> > +	for (i = 0; i < st->info->num_scales; i++) {
> > +		__ad9467_get_scale(st, i, &val1, &val2);
> >  		st->scales[i][0] = val1;
> >  		st->scales[i][1] = val2;
> >  	}
> > @@ -421,11 +437,27 @@ static int ad9467_scale_fill(struct adi_axi_adc_conv
> > *conv)
> >  	return 0;
> >  }
> >  
> > -static int ad9467_preenable_setup(struct adi_axi_adc_conv *conv)
> > +static int ad9467_setup(struct ad9467_state *st)
> >  {
> > -	struct ad9467_state *st = adi_axi_adc_conv_priv(conv);
> > +	struct iio_backend_data_fmt data = {
> > +		.sign_extend = true,
> > +		.enable = true,
> > +	};
> > +	unsigned int c, mode;
> > +	int ret;
> > +
> > +	mode = st->info->default_output_mode |
> > AN877_ADC_OUTPUT_MODE_TWOS_COMPLEMENT;
> 
> Bit of a long line. Perhaps break it after the |

One of those cases where I think going beyond the 80 limit col helps
readability. But I can break the line if that's your preference.
 
> 
> > +	ret = ad9467_outputmode_set(st->spi, mode);
> > +	if (ret)
> > +		return ret;
> >  
> > -	return ad9467_outputmode_set(st->spi, st->output_mode);
> > +	for (c = 0; c < st->info->num_channels; c++) {
> > +		ret = iio_backend_data_format_set(st->back, c, &data);
> > +		if (ret)
> > +			return ret;
> > +	}
> > +
> > +	return 0;
> >  }
> >  
> >  static int ad9467_reset(struct device *dev)
> > @@ -443,25 +475,64 @@ static int ad9467_reset(struct device *dev)
> >  	return 0;
> >  }
> >  
> > +static int ad9467_iio_backend_get(struct ad9467_state *st)
> > +{
> > +	struct device *dev = &st->spi->dev;
> > +	struct device_node *__back;
> > +
> > +	st->back = devm_iio_backend_get(&st->spi->dev, NULL);
> > +	/* If not found, don't error out as we might have legacy DT
> > property */
> > +	if (IS_ERR(st->back) && PTR_ERR(st->back) != -ENOENT)
> > +		return PTR_ERR(st->back);
> > +	if (!IS_ERR(st->back))
> > +		return 0;
> Why not do this one first? I know I normally moan about having error handlers
> out of line, but in this case the good is out of line whatever.
> 
> 	if (!IS_ERR(st->back)
> 		return 0;
> 
> 	if (PTR_ERR(st->back) != ENOENT)
> 		return PTR_ERR(st->back);
> 
> 	...

Yeah, really because I wanted to have the error condition checked first. But I
agree in this particular case it makes the code simpler by not doing it that
way.

> 
> 
> > +	/*
> > +	 * if we don't get the backend using the normal API's, use the
> > legacy
> > +	 * 'adi,adc-dev' property. So we get all nodes with that property,
> > and
> > +	 * look for the one pointing at us. Then we directly lookup that
> > fwnode
> > +	 * on the backend list of registered devices. This is done so we
> > don't
> > +	 * make io-backends mandatory which would break DT ABI.
> > +	 */
> > +	for_each_node_with_property(__back, "adi,adc-dev") {
> > +		struct device_node *__me;
> > +
> > +		__me = of_parse_phandle(__back, "adi,adc-dev", 0);
> > +		if (!__me)
> > +			continue;
> > +
> > +		if (!device_match_of_node(dev, __me)) {
> > +			of_node_put(__me);
> > +			continue;
> > +		}
> > +
> > +		of_node_put(__me);
> > +		st->back = __devm_iio_backend_get_from_fwnode_lookup(dev,
> > +								    
> > of_fwnode_handle(__back));
> > +		of_node_put(__back);
> > +		return PTR_ERR_OR_ZERO(st->back);
> > +	}
> > +
> > +	return -ENODEV;
> > +}
> > +
> >  static int ad9467_probe(struct spi_device *spi)
> >  {
> > 
> 
> >  
> > -	st->output_mode = info->default_output_mode |
> > -			  AN877_ADC_OUTPUT_MODE_TWOS_COMPLEMENT;
> > +	ret = ad9467_iio_backend_get(st);
> > +	if (ret)
> > +		return ret;
> >  
> > -	return 0;
> > +	ret = devm_iio_backend_request_buffer(&spi->dev, st->back,
> > indio_dev);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = iio_backend_enable(st->back);
> > +	if (ret)
> > +		return ret;
> 
> I'm curious there is no iio_backend_disable() to be done in the exit path?
> 

Ehehe something I have in my mind, yes. I'm just not disabling the core because
it was the same with the previous approach. My goal was to have (more or less)
the same state before vs after introducing the backend. I was thinking in adding
a devm_iio_backend_enable() as a follow up patch and use it in here (or actually
use it for the first axi-dac/dds user as that one will be come from a "clean"
state).

If you prefer I can already turn iio_backend_enable() ->
devm_iio_backend_enable() and use it in this patch.

- Nuno Sá
>