linux-kernel - Re: [PATCH v2 19/22] iio: accel: adxl345: prepare FIFO watermark handling

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Message-ID: <20241124190525.51cc08ff@jic23-huawei>
Date: Sun, 24 Nov 2024 19:05:25 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Lothar Rubusch <l.rubusch@...il.com>
Cc: lars@...afoo.de, Michael.Hennerich@...log.com,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
 eraretuya@...il.com
Subject: Re: [PATCH v2 19/22] iio: accel: adxl345: prepare FIFO watermark
 handling

On Sun, 17 Nov 2024 18:26:48 +0000
Lothar Rubusch <l.rubusch@...il.com> wrote:

> Add the feature of the adxl345 and related sensors to manage a FIFO in
> stream mode by a watermark level. Provide means to set the watermark
> through the IIO api and sysfs interface.
> 
> Signed-off-by: Lothar Rubusch <l.rubusch@...il.com>

> +/*
> + * NB: The buffer/hwfifo_watermark is a read-only entry to display the
> + * currently set hardware FIFO watermark. First set a value to buffer0/length.
> + * This allows to configure buffer0/watermark. After enabling buffer0/enable
> + * the hwfifo_watermark shall show the configured FIFO watermark value.
> + *
> + * ref: Documentation/ABI/testing/sysfs-bus-iio
> + */
> +IIO_STATIC_CONST_DEVICE_ATTR(hwfifo_watermark_min, "1");
> +IIO_STATIC_CONST_DEVICE_ATTR(hwfifo_watermark_max,
> +			     __stringify(ADXL34x_FIFO_SIZE));
> +static IIO_DEVICE_ATTR(hwfifo_watermark, 0444,
> +		       adxl345_get_fifo_watermark, NULL, 0);
> +static IIO_DEVICE_ATTR(hwfifo_enabled, 0444,
> +		       adxl345_get_fifo_enabled, NULL, 0);
> +
> +static IIO_DEVICE_ATTR_RW(watermark_en, 0);
> +
>  static const struct iio_dev_attr *adxl345_fifo_attributes[] = {
> +	&iio_dev_attr_hwfifo_watermark_min,
> +	&iio_dev_attr_hwfifo_watermark_max,
> +	&iio_dev_attr_hwfifo_watermark,
> +	&iio_dev_attr_hwfifo_enabled,
>  	NULL,
Introduce the whole array only when you bring in the entries (so here).
>  };
>  
> @@ -345,6 +434,7 @@ static IIO_CONST_ATTR_SAMP_FREQ_AVAIL(
>  
>  static struct attribute *adxl345_attrs[] = {
>  	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
> +	&iio_dev_attr_watermark_en.dev_attr.attr,

Non standard ABI.  This should be indirectly controlled by the
watermark on the software buffer IIRC. (it's been a while
since I last looked at that). 

If the watermark passed to hwfifo_set_watermark is 0 then turn it off.
Otherwise turn it on.


Jonathan

>  	NULL
>  };