Il giorno ven 13 set 2019 alle ore 08:46 Ardelean, Alexandru
<alexandru.Ardelean@xxxxxxxxxx> ha scritto:
>
> On Thu, 2019-09-12 at 16:43 +0200, Andrea Merello wrote:
> > [External]
> >
> > This driver supports 14-bits and 16-bits devices. All of them have a 14-bit
> > configuration registers. All SPI trasfers, for reading AD conversion
> > results and for writing the configuration register, fit in two bytes.
> >
> > The driver always uses 4-bytes xfers which seems at least pointless (maybe
> > even harmful). This patch trims the SPI xfer len and the buffer size to
> > two bytes.
> >
>
> The length reduction proposal is fine.
>
> But, this patch raises a question about endianess.
> I'm actually wondering here if we need to see about maybe using a __be16 vs u16.
>
> I'm not that kernel-savy yet about some of these low-level things to be completely sure here.
> So, I'd let someone else maybe handle it.
Good point.. It seems that indeed not much care has been taken about
endianess here.. Probably we need also some le16_to_cpu() and
firends..
Maybe another separate patch can be made to take care about endianess later on?
BTW Also, the ____cacheline_aligned is a bit scaring :) I don't know
what is that for...
>
> Thanks
> Alex
>
> > Signed-off-by: Andrea Merello <andrea.merello@xxxxxxxxx>
> > ---
> > drivers/iio/adc/ad7949.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> > index 518044c31a73..5c2b3446fa4a 100644
> > --- a/drivers/iio/adc/ad7949.c
> > +++ b/drivers/iio/adc/ad7949.c
> > @@ -54,7 +54,7 @@ struct ad7949_adc_chip {
> > u8 resolution;
> > u16 cfg;
> > unsigned int current_channel;
> > - u32 buffer ____cacheline_aligned;
> > + u16 buffer ____cacheline_aligned;
> > };
> >
> > static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val,
> > @@ -67,7 +67,7 @@ static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val,
> > struct spi_transfer tx[] = {
> > {
> > .tx_buf = &ad7949_adc->buffer,
> > - .len = 4,
> > + .len = 2,
> > .bits_per_word = bits_per_word,
> > },
> > };
> > @@ -95,7 +95,7 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
> > struct spi_transfer tx[] = {
> > {
> > .rx_buf = &ad7949_adc->buffer,
> > - .len = 4,
> > + .len = 2,
> > .bits_per_word = bits_per_word,
> > },
> > };
