[v1] iio: introduce IIO_DECLARE_BUFFER_WITH_TS

[PATCH 2/4] iio: adc: ad4695: use IIO_DECLARE_BUFFER_WITH_TS

Posted by David Lechner 7 months, 4 weeks ago

Use IIO_DECLARE_BUFFER_WITH_TS to declare the buffer that gets used with
iio_push_to_buffers_with_ts(). This makes the code a bit easier to read
and understand.

AD4695_MAX_CHANNEL_SIZE macro is dropped since it was making the line
too long and didn't add that much value.

AD4695_MAX_CHANNELS + 2 is changed to AD4695_MAX_CHANNELS + 1 because
previously we were overallocating. AD4695_MAX_CHANNELS is the number of
of voltage channels and + 1 is for the temperature channel.

Signed-off-by: David Lechner <dlechner@baylibre.com>
---
 drivers/iio/adc/ad4695.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/ad4695.c b/drivers/iio/adc/ad4695.c
index 68c6625db0d75f4cade7cb029e94191118dbcaa0..9862ff99642b61db42b16b797ae046efd99c2811 100644
--- a/drivers/iio/adc/ad4695.c
+++ b/drivers/iio/adc/ad4695.c
@@ -106,8 +106,6 @@
 
 /* Max number of voltage input channels. */
 #define AD4695_MAX_CHANNELS		16
-/* Max size of 1 raw sample in bytes. */
-#define AD4695_MAX_CHANNEL_SIZE		2
 
 enum ad4695_in_pair {
 	AD4695_IN_PAIR_REFGND,
@@ -162,8 +160,8 @@ struct ad4695_state {
 	struct spi_transfer buf_read_xfer[AD4695_MAX_CHANNELS * 2 + 3];
 	struct spi_message buf_read_msg;
 	/* Raw conversion data received. */
-	u8 buf[ALIGN((AD4695_MAX_CHANNELS + 2) * AD4695_MAX_CHANNEL_SIZE,
-		     sizeof(s64)) + sizeof(s64)] __aligned(IIO_DMA_MINALIGN);
+	IIO_DECLARE_BUFFER_WITH_TS(u8, buf, (AD4695_MAX_CHANNELS + 1) * 2)
+		__aligned(IIO_DMA_MINALIGN);
 	u16 raw_data;
 	/* Commands to send for single conversion. */
 	u16 cnv_cmd;

-- 
2.43.0

Re: [PATCH 2/4] iio: adc: ad4695: use IIO_DECLARE_BUFFER_WITH_TS

Posted by Andy Shevchenko 7 months, 4 weeks ago

On Fri, Apr 18, 2025 at 05:58:33PM -0500, David Lechner wrote:
> Use IIO_DECLARE_BUFFER_WITH_TS to declare the buffer that gets used with
> iio_push_to_buffers_with_ts(). This makes the code a bit easier to read
> and understand.
> 
> AD4695_MAX_CHANNEL_SIZE macro is dropped since it was making the line
> too long and didn't add that much value.
> 
> AD4695_MAX_CHANNELS + 2 is changed to AD4695_MAX_CHANNELS + 1 because
> previously we were overallocating. AD4695_MAX_CHANNELS is the number of
> of voltage channels and + 1 is for the temperature channel.

...

> -/* Max size of 1 raw sample in bytes. */
> -#define AD4695_MAX_CHANNEL_SIZE		2

>  	/* Raw conversion data received. */
> -	u8 buf[ALIGN((AD4695_MAX_CHANNELS + 2) * AD4695_MAX_CHANNEL_SIZE,
> -		     sizeof(s64)) + sizeof(s64)] __aligned(IIO_DMA_MINALIGN);
> +	IIO_DECLARE_BUFFER_WITH_TS(u8, buf, (AD4695_MAX_CHANNELS + 1) * 2)
> +		__aligned(IIO_DMA_MINALIGN);

I would rather expect this to be properly written as u16 / __le16 / __be16
instead of playing tricks with u8.

With all comments given so far I would expect here something like:

	IIO_DECLARE_BUFFER_WITH_TS(u16, buf, AD4695_MAX_CHANNELS + 1);


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 2/4] iio: adc: ad4695: use IIO_DECLARE_BUFFER_WITH_TS

Posted by David Lechner 7 months, 4 weeks ago

On 4/19/25 11:38 AM, Andy Shevchenko wrote:
> On Fri, Apr 18, 2025 at 05:58:33PM -0500, David Lechner wrote:
>> Use IIO_DECLARE_BUFFER_WITH_TS to declare the buffer that gets used with
>> iio_push_to_buffers_with_ts(). This makes the code a bit easier to read
>> and understand.
>>
>> AD4695_MAX_CHANNEL_SIZE macro is dropped since it was making the line
>> too long and didn't add that much value.
>>
>> AD4695_MAX_CHANNELS + 2 is changed to AD4695_MAX_CHANNELS + 1 because
>> previously we were overallocating. AD4695_MAX_CHANNELS is the number of
>> of voltage channels and + 1 is for the temperature channel.
> 
> ...
> 
>> -/* Max size of 1 raw sample in bytes. */
>> -#define AD4695_MAX_CHANNEL_SIZE		2
> 
>>  	/* Raw conversion data received. */
>> -	u8 buf[ALIGN((AD4695_MAX_CHANNELS + 2) * AD4695_MAX_CHANNEL_SIZE,
>> -		     sizeof(s64)) + sizeof(s64)] __aligned(IIO_DMA_MINALIGN);
>> +	IIO_DECLARE_BUFFER_WITH_TS(u8, buf, (AD4695_MAX_CHANNELS + 1) * 2)
>> +		__aligned(IIO_DMA_MINALIGN);
> 
> I would rather expect this to be properly written as u16 / __le16 / __be16
> instead of playing tricks with u8.
> 
> With all comments given so far I would expect here something like:
> 
> 	IIO_DECLARE_BUFFER_WITH_TS(u16, buf, AD4695_MAX_CHANNELS + 1);
> 
> 

We would have to make significant changes to the driver to allow u16 instead
of u8. I don't remember why I did it that way in the first place, but I consider
changing it out of scope for this patch.

Re: [PATCH 2/4] iio: adc: ad4695: use IIO_DECLARE_BUFFER_WITH_TS

Posted by Jonathan Cameron 7 months, 3 weeks ago

On Sat, 19 Apr 2025 12:57:11 -0500
David Lechner <dlechner@baylibre.com> wrote:

> On 4/19/25 11:38 AM, Andy Shevchenko wrote:
> > On Fri, Apr 18, 2025 at 05:58:33PM -0500, David Lechner wrote:  
> >> Use IIO_DECLARE_BUFFER_WITH_TS to declare the buffer that gets used with
> >> iio_push_to_buffers_with_ts(). This makes the code a bit easier to read
> >> and understand.
> >>
> >> AD4695_MAX_CHANNEL_SIZE macro is dropped since it was making the line
> >> too long and didn't add that much value.
> >>
> >> AD4695_MAX_CHANNELS + 2 is changed to AD4695_MAX_CHANNELS + 1 because
> >> previously we were overallocating. AD4695_MAX_CHANNELS is the number of
> >> of voltage channels and + 1 is for the temperature channel.  
> > 
> > ...
> >   
> >> -/* Max size of 1 raw sample in bytes. */
> >> -#define AD4695_MAX_CHANNEL_SIZE		2  
> >   
> >>  	/* Raw conversion data received. */
> >> -	u8 buf[ALIGN((AD4695_MAX_CHANNELS + 2) * AD4695_MAX_CHANNEL_SIZE,
> >> -		     sizeof(s64)) + sizeof(s64)] __aligned(IIO_DMA_MINALIGN);
> >> +	IIO_DECLARE_BUFFER_WITH_TS(u8, buf, (AD4695_MAX_CHANNELS + 1) * 2)
> >> +		__aligned(IIO_DMA_MINALIGN);  
> > 
> > I would rather expect this to be properly written as u16 / __le16 / __be16
> > instead of playing tricks with u8.
> > 
> > With all comments given so far I would expect here something like:
> > 
> > 	IIO_DECLARE_BUFFER_WITH_TS(u16, buf, AD4695_MAX_CHANNELS + 1);
> > 
> >   
> 
> We would have to make significant changes to the driver to allow u16 instead
> of u8. I don't remember why I did it that way in the first place, but I consider
> changing it out of scope for this patch.

There are drivers where the size varies depending on the exact part.
Maybe this is a cut and paste from one of those or you thought this might get
bigger to support > 16bit channels in the future.  Either way, right now
it is always 16 bits so an appropriately sized type would be good as you
say.   I think such a change should be in a precursor patch probably
rather than left for another day.  Looks trivial to me given st->buf
is only accessed directly in 2 places.

Jonathan