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

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Date:   Sun, 17 Sep 2023 10:26:15 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Matti Vaittinen <mazziesaccount@...il.com>
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 Thu, 14 Sep 2023 14:47:44 +0300
Matti Vaittinen <mazziesaccount@...il.com> wrote:

> 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.

You could make the exclusive nature obvious in the thread_handler by using an
else if () above. 

> 
> 
> Yours,
> 	-- Matti
> 
> 
>