linux-kernel - Re: [PATCH v1 13/17] iio: chemical: bme680: Add read buffers in DMA safe region

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Date: Mon, 3 Jun 2024 20:27:30 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Vasileios Amoiridis <vassilisamir@...il.com>
Cc: lars@...afoo.de, himanshujha199640@...il.com, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 13/17] iio: chemical: bme680: Add read buffers in DMA
 safe region

On Sun, 2 Jun 2024 21:33:10 +0200
Vasileios Amoiridis <vassilisamir@...il.com> wrote:

> On Sun, Jun 02, 2024 at 01:59:08PM +0100, Jonathan Cameron wrote:
> > On Mon, 27 May 2024 20:38:01 +0200
> > Vasileios Amoiridis <vassilisamir@...il.com> wrote:
> >   
> > > Move the buffers that are used in order to read data from the
> > > device in a DMA-safe region. Also create defines for the number
> > > of bytes that are being read from the device and don't use
> > > magic numbers.
> > > 
> > > Signed-off-by: Vasileios Amoiridis <vassilisamir@...il.com>  
> > 
> > Same response as previous.  I don't think it's necessary because
> > of the custom regmap implementation.
> > 
> > My first instinct was the same as yours though!
> > 
> > Jonathan
> > 
> >   
> Well, even if we end up not needing it, I would keep the values inside
> the union just becasue it saves some space, and it keeps all the read
> buffers in the same place. What do you think?
> 
Sure. The union is fine as long as you have made sure there can't be
concurrent access to the different members. It will save space on x86_64
at least as that has very low IIO_DMA_MINALIGN.  Less likely to make
a difference on arm64.