linux-kernel - Re: [PATCH v2 07/10] iio: adc: ad7476: Conditionally call convstart

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Message-ID: <jqq73v23juc3wj3ykq5df3mevjatnq3zb2aq4w524xnl4xgban@qemnvtvs2twn>
Date: Thu, 7 Aug 2025 13:47:36 +0100
From: Nuno Sá <noname.nuno@...il.com>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>, 
	Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich <Michael.Hennerich@...log.com>, 
	Jonathan Cameron <jic23@...nel.org>, David Lechner <dlechner@...libre.com>, 
	Nuno Sá <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, linux-iio@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 07/10] iio: adc: ad7476: Conditionally call convstart

On Thu, Aug 07, 2025 at 12:35:03PM +0300, Matti Vaittinen wrote:
> The ad7476 supports two IC variants which may have a 'convstart' -GPIO
> for starting the conversion. Currently the driver calls a function which
> tries to access the GPIO for all of the IC variants, whether they
> support 'convstart' or not. This is not an error because this function
> returns early if GPIO information is not populated.
> 
> We can do a tad better by calling this function only for the ICs which
> have the 'convstart' by providing a function pointer to the convstart
> function from the chip_info structure, and calling this function only
> for the ICs which have the function pointer set.
> 
> This does also allow to support ICs which require different convstart
> handling than the currently supported ICs.
> 
> Call convstart function only on the ICs which can support it and allow
> IC-specific convstart functions for the ICs which require different
> handling.
> 
> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
> ---
> Revision history:
>  v1 => v2:
>  - Adapt to the change which removed the chip_info pointer from the
>   driver's state structure.
> 
> The follow-up patch adding support for the ROHM BD79105 will bring
> different 'convstart' functions in use. The IC specific pointer will
> also prepare the way for this.
> ---
>  drivers/iio/adc/ad7476.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/ad7476.c b/drivers/iio/adc/ad7476.c
> index a30eb016c11c..8914861802be 100644
> --- a/drivers/iio/adc/ad7476.c
> +++ b/drivers/iio/adc/ad7476.c
> @@ -30,6 +30,7 @@ struct ad7476_chip_info {
>  	unsigned int			int_vref_mv;
>  	struct iio_chan_spec		channel[2];
>  	void (*reset)(struct ad7476_state *);
> +	void (*conversion_pre_op)(struct ad7476_state *st);
>  	bool				has_vref;
>  	bool				has_vdrive;
>  };
> @@ -37,6 +38,7 @@ struct ad7476_chip_info {
>  struct ad7476_state {
>  	struct spi_device		*spi;
>  	struct gpio_desc		*convst_gpio;
> +	void (*conversion_pre_op)(struct ad7476_state *st);

Ok, I was going to reply to patch patch 5 saying I was not sure about
the change. And now this makes it clear. My point would be that it's
fairly easiy to end up needing chip info after probe. The above function
pointer only has to exist because of patch 5. So I would better drop
patch 5 and...

>  	struct spi_transfer		xfer;
>  	struct spi_message		msg;
>  	struct iio_chan_spec		channel[2];
> @@ -68,7 +70,8 @@ static irqreturn_t ad7476_trigger_handler(int irq, void  *p)
>  	struct ad7476_state *st = iio_priv(indio_dev);
>  	int b_sent;
>  
> -	ad7091_convst(st);
> +	if (st->conversion_pre_op)
> +		st->conversion_pre_op(st);
>  
>  	b_sent = spi_sync(st->spi, &st->msg);
>  	if (b_sent < 0)
> @@ -158,12 +161,14 @@ static int ad7476_read_raw(struct iio_dev *indio_dev,
>  static const struct ad7476_chip_info ad7091_chip_info = {
>  	.channel[0] = AD7091R_CHAN(12),
>  	.channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
> +	.conversion_pre_op = ad7091_convst,
>  	.reset = ad7091_reset,
>  };
>  
>  static const struct ad7476_chip_info ad7091r_chip_info = {
>  	.channel[0] = AD7091R_CHAN(12),
>  	.channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
> +	.conversion_pre_op = ad7091_convst,
>  	.int_vref_mv = 2500,
>  	.has_vref = true,
>  	.reset = ad7091_reset,
> @@ -319,6 +324,7 @@ static int ad7476_probe(struct spi_device *spi)
>  			return ret;
>  	}
>  
> +	st->conversion_pre_op = chip_info->conversion_pre_op;

... no need for the above. There's no real reason for the above to be
done at runtime.

- Nuno Sá

>  	st->convst_gpio = devm_gpiod_get_optional(&spi->dev,
>  						  "adi,conversion-start",
>  						  GPIOD_OUT_LOW);
> -- 
> 2.50.1
>