Date: Fri, 15 Mar 2024 14:28:30 +0100
From: Angel Iglesias <ang.iglesiasg@...il.com>
To: Vasileios Amoiridis <vassilisamir@...il.com>
Cc: Jonathan Cameron <jic23@...nel.org>, lars@...afoo.de, 
 andriy.shevchenko@...ux.intel.com, mazziesaccount@...il.com,
 ak@...klinger.de,  petre.rodan@...dimension.ro, linus.walleij@...aro.org,
 phil@...pberrypi.com,  579lpy@...il.com, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/6] iio: pressure: Simplify and make more clear
 temperature readings

On Fri, 2024-03-15 at 10:05 +0100, Vasileios Amoiridis wrote:
> On Fri, Mar 15, 2024 at 12:22:50AM +0100, Angel Iglesias wrote:
> > On Thu, 2024-03-14 at 21:17 +0100, Vasileios Amoiridis wrote:
> > > On Thu, Mar 14, 2024 at 03:09:59PM +0000, Jonathan Cameron wrote:
> > > > On Wed, 13 Mar 2024 18:40:05 +0100
> > > > Vasileios Amoiridis <vassilisamir@...il.com> wrote:
> > > > 
> > > > > The read_press/read_humid functions need the updated t_fine value
> > > > > in order to calculate the current pressure/humidity. Temperature
> > > > > reads should be removed from the read_press/read_humid functions
> > > > > and should be placed in the oneshot captures before the pressure
> > > > > and humidity reads. This makes the code more intuitive.
> > > > > 
> > > > > Signed-off-by: Vasileios Amoiridis <vassilisamir@...il.com>
> > > > 
> > > > To me this makes the use of these calls less obvious than they were
> > > > previously.  The calls are made close to where t_fine is used and
> > > > don't have to go via the indirection of chip_info.
> > > > 
> > > > So I disagree. I think this change makes the code a lot less
> > > > clear.
> > > > 
> > > 
> > > This was mainly driven by the fact that I wanted to avoid reading
> > > the temperature 3 times in case temp, press and humid are enabled
> > > and there are consecutive buffer readings. But thank you for the
> > > proposal I really appreciate it!
> > > 
> > 
> > Hi, just a side note reflecting on this. Depending on your sampling
> > frequency
> > and registers data shadowing, to avoid compensating with different samples
> > between readings, we should be doing burst readings to get a bundle of the
> > temperature+pressure and/or humidity.
> > On the bmp/bme280 and bmp380 this can be done as registers are contiguous on
> > the
> > memory. On the bmp580 this is not a problem as the values are already
> > compensated, you`ll get always the latest reading.
> > 
> > Kind regard,
> > Angel
> 
> Hi Angel,
> 
> Thank you for pointing this out! Indeed that's true but I noticed that this is
> not
> the case for the BMP{085/180} devices. I just feel that some changes might
> make
> data acquisition/processing faster for a device (like the one you proposed)
> but
> it might make the code much more unreadable and unmaintanable. I will try and
> see if something could be done in that sense but I feel that keeping it simple
> will
> be good for everyone!
> 
> Cheers,
> Vasilis

Yeah, data adquisition on bmp085/180 is already different as they don't support
continuous mode as the newer models and you have to warm-up the sensor and do
one-shot readings. There's already a different code path in place for that
models. I guess that is the price to pay to support that wide range of
sensors...
Anyway, this patches are already big and you're doing quite a lot of heavy-
lifting right now, so don't pay much attention to my ramblings! Regardless,
happy to help with tasks polishing and updating this driver :)

Kind regards,
Angel

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