linux-kernel - Re: [PATCH 2/3] iio: pressure: Support ROHM BU1390

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Date:   Thu, 14 Sep 2023 14:47:44 +0300
From:   Matti Vaittinen <mazziesaccount@...il.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Angel Iglesias <ang.iglesiasg@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andreas Klinger <ak@...klinger.de>, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] iio: pressure: Support ROHM BU1390

On 9/10/23 16:22, Jonathan Cameron wrote:
> On Wed, 6 Sep 2023 15:37:48 +0300
> Matti Vaittinen <mazziesaccount@...il.com> wrote:
> 
>> Support for the ROHM BM1390 pressure sensor. The BM1390GLV-Z can measure
>> pressures ranging from 300 hPa to 1300 hPa with configurable measurement
>> averaging and internal FIFO. The sensor does also provide temperature
>> measurements.
>>
>> Sensor does also contain IIR filter implemented in HW. The data-sheet
>> says the IIR filter can be configured to be "weak", "middle" or
>> "strong". Some RMS noise figures are provided in data sheet but no
>> accurate maths for the filter configurations is provided. Hence, the IIR
>> filter configuration is not supported by this driver and the filter is
>> configured to the "middle" setting (at least not for now).

>> +
>> +static irqreturn_t bm1390_irq_thread_handler(int irq, void *private)
>> +{
>> +	struct iio_dev *idev = private;
>> +	struct bm1390_data *data = iio_priv(idev);
>> +	int ret = IRQ_NONE;
>> +
>> +	mutex_lock(&data->mutex);
>> +
>> +	if (data->trigger_enabled) {
>> +		iio_trigger_poll_nested(data->trig);
>> +		ret = IRQ_HANDLED;
>> +	}
>> +
>> +	if (data->state == BM1390_STATE_FIFO) {
> 
> Can this and trigger_enabled be true?

Thanks for asking this question. Intention was that these are mutually 
exclusive. However, I think that the check
if (iio_device_get_current_mode(idev) == INDIO_BUFFER_TRIGGERED)
in bm1390_buffer_postenable(), before calling the bm1390_fifo_enable() 
is not 100% race free.

I, however, like the idea of having this check in the buffer-enable 
function - I think it makes the design much more obvious. What I will do 
is adding another check for:
	if (data->trigger_enable) {
		ret = -EBUSY;
		goto unlock_out;
	}

inside the bm1390_fifo_enable() to the section which holds the mutex.


Yours,
	-- Matti



-- 
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

~~ When things go utterly wrong vim users can always type :help! ~~