The register data is 12-bit big-endian data. Use be16_to_cpu() to do
the conversion, and simple bitwise AND for masking to make it more
obvious.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
---
Revision history:
v1 => v2:
 - Fix commit msg to reflect the fact there was no bug
 - Drop Fixes tag
 - Use union for rx / tx buffer to avoid casting
 - Keep the shared message protected by the mutex
---
 drivers/iio/adc/ti-adc128s052.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
index a456ea78462f..3e69a5fce010 100644
--- a/drivers/iio/adc/ti-adc128s052.c
+++ b/drivers/iio/adc/ti-adc128s052.c
@@ -28,32 +28,34 @@ struct adc128 {
 	struct regulator *reg;
 	struct mutex lock;
 
-	u8 buffer[2] __aligned(IIO_DMA_MINALIGN);
+	union {
+		__be16 rx_buffer;
+		u8 tx_buffer[2];
+	} __aligned(IIO_DMA_MINALIGN);
 };
 
 static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
 {
 	int ret;
+	char *msg = &adc->tx_buffer[0];
 
 	mutex_lock(&adc->lock);
 
-	adc->buffer[0] = channel << 3;
-	adc->buffer[1] = 0;
+	msg[0] = channel << 3;
+	msg[1] = 0;
 
-	ret = spi_write(adc->spi, &adc->buffer, 2);
+	ret = spi_write(adc->spi, msg, sizeof(adc->tx_buffer));
 	if (ret < 0) {
 		mutex_unlock(&adc->lock);
 		return ret;
 	}
 
-	ret = spi_read(adc->spi, &adc->buffer, 2);
-
+	ret = spi_read(adc->spi, &adc->rx_buffer, 2);
 	mutex_unlock(&adc->lock);
-
 	if (ret < 0)
 		return ret;
 
-	return ((adc->buffer[0] << 8 | adc->buffer[1]) & 0xFFF);
+	return be16_to_cpu(adc->rx_buffer) & 0xFFF;
 }
 
 static int adc128_read_raw(struct iio_dev *indio_dev,
-- 
2.49.0

On 4/2/25 1:09 AM, Matti Vaittinen wrote:
> The register data is 12-bit big-endian data. Use be16_to_cpu() to do
> the conversion, and simple bitwise AND for masking to make it more
> obvious.
> 
> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
> ---
> Revision history:
> v1 => v2:
>  - Fix commit msg to reflect the fact there was no bug
>  - Drop Fixes tag
>  - Use union for rx / tx buffer to avoid casting
>  - Keep the shared message protected by the mutex
> ---
>  drivers/iio/adc/ti-adc128s052.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
> index a456ea78462f..3e69a5fce010 100644
> --- a/drivers/iio/adc/ti-adc128s052.c
> +++ b/drivers/iio/adc/ti-adc128s052.c
> @@ -28,32 +28,34 @@ struct adc128 {
>  	struct regulator *reg;
>  	struct mutex lock;
>  
> -	u8 buffer[2] __aligned(IIO_DMA_MINALIGN);
> +	union {
> +		__be16 rx_buffer;
> +		u8 tx_buffer[2];
> +	} __aligned(IIO_DMA_MINALIGN);
>  };
>  
>  static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
>  {
>  	int ret;
> +	char *msg = &adc->tx_buffer[0];
>  
>  	mutex_lock(&adc->lock);
>  
> -	adc->buffer[0] = channel << 3;
> -	adc->buffer[1] = 0;
> +	msg[0] = channel << 3;
> +	msg[1] = 0;
>  
> -	ret = spi_write(adc->spi, &adc->buffer, 2);
> +	ret = spi_write(adc->spi, msg, sizeof(adc->tx_buffer));
>  	if (ret < 0) {
>  		mutex_unlock(&adc->lock);
>  		return ret;
>  	}
>  
> -	ret = spi_read(adc->spi, &adc->buffer, 2);
> -
> +	ret = spi_read(adc->spi, &adc->rx_buffer, 2);
>  	mutex_unlock(&adc->lock);
> -
>  	if (ret < 0)
>  		return ret;
>  
> -	return ((adc->buffer[0] << 8 | adc->buffer[1]) & 0xFFF);
> +	return be16_to_cpu(adc->rx_buffer) & 0xFFF;


The cast isn't exactly beautiful, but this would save a lot of
lines of diff and a few lines of code by avoiding the need for
the union and the local msg variable.

	return be16_to_cpup((__be16 *)adc->buffer) & 0xFFF;

>  }
>  
>  static int adc128_read_raw(struct iio_dev *indio_dev,

On 03/04/2025 00:04, David Lechner wrote:
> On 4/2/25 1:09 AM, Matti Vaittinen wrote:
>> The register data is 12-bit big-endian data. Use be16_to_cpu() to do
>> the conversion, and simple bitwise AND for masking to make it more
>> obvious.
>>
>> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
>> ---
>> Revision history:
>> v1 => v2:
>>   - Fix commit msg to reflect the fact there was no bug
>>   - Drop Fixes tag
>>   - Use union for rx / tx buffer to avoid casting
>>   - Keep the shared message protected by the mutex
>> ---
>>   drivers/iio/adc/ti-adc128s052.c | 18 ++++++++++--------
>>   1 file changed, 10 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
>> index a456ea78462f..3e69a5fce010 100644
>> --- a/drivers/iio/adc/ti-adc128s052.c
>> +++ b/drivers/iio/adc/ti-adc128s052.c
>> @@ -28,32 +28,34 @@ struct adc128 {
>>   	struct regulator *reg;
>>   	struct mutex lock;
>>   
>> -	u8 buffer[2] __aligned(IIO_DMA_MINALIGN);
>> +	union {
>> +		__be16 rx_buffer;
>> +		u8 tx_buffer[2];
>> +	} __aligned(IIO_DMA_MINALIGN);
>>   };
>>   
>>   static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
>>   {
>>   	int ret;
>> +	char *msg = &adc->tx_buffer[0];
>>   
>>   	mutex_lock(&adc->lock);
>>   
>> -	adc->buffer[0] = channel << 3;
>> -	adc->buffer[1] = 0;
>> +	msg[0] = channel << 3;
>> +	msg[1] = 0;
>>   
>> -	ret = spi_write(adc->spi, &adc->buffer, 2);
>> +	ret = spi_write(adc->spi, msg, sizeof(adc->tx_buffer));
>>   	if (ret < 0) {
>>   		mutex_unlock(&adc->lock);
>>   		return ret;
>>   	}
>>   
>> -	ret = spi_read(adc->spi, &adc->buffer, 2);
>> -
>> +	ret = spi_read(adc->spi, &adc->rx_buffer, 2);
>>   	mutex_unlock(&adc->lock);
>> -
>>   	if (ret < 0)
>>   		return ret;
>>   
>> -	return ((adc->buffer[0] << 8 | adc->buffer[1]) & 0xFFF);
>> +	return be16_to_cpu(adc->rx_buffer) & 0xFFF;
> 
> 
> The cast isn't exactly beautiful, but this would save a lot of
> lines of diff and a few lines of code by avoiding the need for
> the union and the local msg variable.
> 
> 	return be16_to_cpup((__be16 *)adc->buffer) & 0xFFF;

Thanks again for the review David :)

I am unsure which way to go. I kind of like having the __be16 in the 
struct, as it immediately yells "data from device is big-endian". OTOH, 
I've never loved unions (and, it silences the above "yelling" quite a 
bit). I still think this might be the first time I really see a valid 
use-case for an union :) And, you're right this adds more lines, 
besides, the cast doesn't look that ugly to me. Yet, I originally had a 
cast probably as simple as this (and I also had the __be16 in the 
struct), and Jonathan suggested using union to avoid it...

At the end of the day, I suppose I am Okay with any of these 3 
approaches. Original cast, union or this cast you suggest. Jonathan, any 
preferences on your side?

> 
>>   }
>>   
>>   static int adc128_read_raw(struct iio_dev *indio_dev,
> 

Yours,
	-- Matti

On Thu, 3 Apr 2025 08:16:43 +0300
Matti Vaittinen <mazziesaccount@gmail.com> wrote:

> On 03/04/2025 00:04, David Lechner wrote:
> > On 4/2/25 1:09 AM, Matti Vaittinen wrote:  
> >> The register data is 12-bit big-endian data. Use be16_to_cpu() to do
> >> the conversion, and simple bitwise AND for masking to make it more
> >> obvious.
> >>
> >> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
> >> ---
> >> Revision history:
> >> v1 => v2:
> >>   - Fix commit msg to reflect the fact there was no bug
> >>   - Drop Fixes tag
> >>   - Use union for rx / tx buffer to avoid casting
> >>   - Keep the shared message protected by the mutex
> >> ---
> >>   drivers/iio/adc/ti-adc128s052.c | 18 ++++++++++--------
> >>   1 file changed, 10 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
> >> index a456ea78462f..3e69a5fce010 100644
> >> --- a/drivers/iio/adc/ti-adc128s052.c
> >> +++ b/drivers/iio/adc/ti-adc128s052.c
> >> @@ -28,32 +28,34 @@ struct adc128 {
> >>   	struct regulator *reg;
> >>   	struct mutex lock;
> >>   
> >> -	u8 buffer[2] __aligned(IIO_DMA_MINALIGN);
> >> +	union {
> >> +		__be16 rx_buffer;
> >> +		u8 tx_buffer[2];
As below. Maybe
		__be16 buffer16;
		u8 buffer[2];

> >> +	} __aligned(IIO_DMA_MINALIGN);
> >>   };
> >>   
> >>   static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
> >>   {
> >>   	int ret;
> >> +	char *msg = &adc->tx_buffer[0];
> >>   
> >>   	mutex_lock(&adc->lock);
> >>   
> >> -	adc->buffer[0] = channel << 3;
> >> -	adc->buffer[1] = 0;
> >> +	msg[0] = channel << 3;
> >> +	msg[1] = 0;
> >>   
> >> -	ret = spi_write(adc->spi, &adc->buffer, 2);
> >> +	ret = spi_write(adc->spi, msg, sizeof(adc->tx_buffer));

I'd get rid of msg as it's now just confusing given we are
using the sizeof() here.

> >>   	if (ret < 0) {
> >>   		mutex_unlock(&adc->lock);
> >>   		return ret;
> >>   	}
> >>   
> >> -	ret = spi_read(adc->spi, &adc->buffer, 2);
> >> -
> >> +	ret = spi_read(adc->spi, &adc->rx_buffer, 2);

sizeof(adc->rx_buffer)

> >>   	mutex_unlock(&adc->lock);
> >> -
> >>   	if (ret < 0)
> >>   		return ret;
> >>   
> >> -	return ((adc->buffer[0] << 8 | adc->buffer[1]) & 0xFFF);
> >> +	return be16_to_cpu(adc->rx_buffer) & 0xFFF;  
> > 
> > 
> > The cast isn't exactly beautiful, but this would save a lot of
> > lines of diff and a few lines of code by avoiding the need for
> > the union and the local msg variable.
> > 
> > 	return be16_to_cpup((__be16 *)adc->buffer) & 0xFFF;  

The cast only works because we have forced the alignment for DMA safety.
That to me is a little fragile.

You could do get_unaligned_be16() which doesn't need the cast then carry
on using the original buffer.  

> 
> Thanks again for the review David :)
> 
> I am unsure which way to go. I kind of like having the __be16 in the 
> struct, as it immediately yells "data from device is big-endian". OTOH, 
> I've never loved unions (and, it silences the above "yelling" quite a 
> bit). I still think this might be the first time I really see a valid 
> use-case for an union :) And, you're right this adds more lines, 
> besides, the cast doesn't look that ugly to me. Yet, I originally had a 
> cast probably as simple as this (and I also had the __be16 in the 
> struct), and Jonathan suggested using union to avoid it...
> 
> At the end of the day, I suppose I am Okay with any of these 3 
> approaches. Original cast, union or this cast you suggest. Jonathan, any 
> preferences on your side?

Majority of the diff is really about renaming buffer to tx_buffer.
Could just not bother doing that and instead have buffer and buffer16
as the two union elements. With msg gone as suggested above, then the diff
becomes only a few lines and you get to keep the nicety of it being either
a pair of u8s or a __be16.

Jonathan

> 
> >   
> >>   }
> >>   
> >>   static int adc128_read_raw(struct iio_dev *indio_dev,  
> >   
> 
> Yours,
> 	-- Matti
>

On 05/04/2025 20:29, Jonathan Cameron wrote:
> On Thu, 3 Apr 2025 08:16:43 +0300
> Matti Vaittinen <mazziesaccount@gmail.com> wrote:
> 
>> On 03/04/2025 00:04, David Lechner wrote:
>>> On 4/2/25 1:09 AM, Matti Vaittinen wrote:
>>>> The register data is 12-bit big-endian data. Use be16_to_cpu() to do
>>>> the conversion, and simple bitwise AND for masking to make it more
>>>> obvious.
>>>>
>>>> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
>>>> ---
>>>> Revision history:
>>>> v1 => v2:
>>>>    - Fix commit msg to reflect the fact there was no bug
>>>>    - Drop Fixes tag
>>>>    - Use union for rx / tx buffer to avoid casting
>>>>    - Keep the shared message protected by the mutex
>>>> ---
>>>>    drivers/iio/adc/ti-adc128s052.c | 18 ++++++++++--------
>>>>    1 file changed, 10 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
>>>> index a456ea78462f..3e69a5fce010 100644
>>>> --- a/drivers/iio/adc/ti-adc128s052.c
>>>> +++ b/drivers/iio/adc/ti-adc128s052.c
>>>> @@ -28,32 +28,34 @@ struct adc128 {
>>>>    	struct regulator *reg;
>>>>    	struct mutex lock;
>>>>    
>>>> -	u8 buffer[2] __aligned(IIO_DMA_MINALIGN);
>>>> +	union {
>>>> +		__be16 rx_buffer;
>>>> +		u8 tx_buffer[2];
> As below. Maybe
> 		__be16 buffer16;
> 		u8 buffer[2];

Ok.

>>>> +	} __aligned(IIO_DMA_MINALIGN);
>>>>    };
>>>>    
>>>>    static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
>>>>    {
>>>>    	int ret;
>>>> +	char *msg = &adc->tx_buffer[0];
>>>>    
>>>>    	mutex_lock(&adc->lock);
>>>>    
>>>> -	adc->buffer[0] = channel << 3;
>>>> -	adc->buffer[1] = 0;
>>>> +	msg[0] = channel << 3;
>>>> +	msg[1] = 0;
>>>>    
>>>> -	ret = spi_write(adc->spi, &adc->buffer, 2);
>>>> +	ret = spi_write(adc->spi, msg, sizeof(adc->tx_buffer));
> 
> I'd get rid of msg as it's now just confusing given we are
> using the sizeof() here.

Ok.

>>>>    	if (ret < 0) {
>>>>    		mutex_unlock(&adc->lock);
>>>>    		return ret;
>>>>    	}
>>>>    
>>>> -	ret = spi_read(adc->spi, &adc->buffer, 2);
>>>> -
>>>> +	ret = spi_read(adc->spi, &adc->rx_buffer, 2);
> 
> sizeof(adc->rx_buffer)

I was thinking of this but went with raw 2 - because we need to read 
exactly 2 bytes from the device. Sizeof buffer is matter of software 
where as the 2 bytes is dictated by the device. (Sure the size of buffer 
needs to be large enough).

I don't care it that much though, so I can go with the sizeof() if 
that's what you prefer. Just explaining that the '2' here was a 
conscious choice :)

>>>>    	mutex_unlock(&adc->lock);
>>>> -
>>>>    	if (ret < 0)
>>>>    		return ret;
>>>>    
>>>> -	return ((adc->buffer[0] << 8 | adc->buffer[1]) & 0xFFF);
>>>> +	return be16_to_cpu(adc->rx_buffer) & 0xFFF;
>>>
>>>
>>> The cast isn't exactly beautiful, but this would save a lot of
>>> lines of diff and a few lines of code by avoiding the need for
>>> the union and the local msg variable.
>>>
>>> 	return be16_to_cpup((__be16 *)adc->buffer) & 0xFFF;
> 
> The cast only works because we have forced the alignment for DMA safety.
> That to me is a little fragile.
> 
> You could do get_unaligned_be16() which doesn't need the cast then carry
> on using the original buffer.
>>
>> Thanks again for the review David :)
>>
>> I am unsure which way to go. I kind of like having the __be16 in the
>> struct, as it immediately yells "data from device is big-endian". OTOH,
>> I've never loved unions (and, it silences the above "yelling" quite a
>> bit). I still think this might be the first time I really see a valid
>> use-case for an union :) And, you're right this adds more lines,
>> besides, the cast doesn't look that ugly to me. Yet, I originally had a
>> cast probably as simple as this (and I also had the __be16 in the
>> struct), and Jonathan suggested using union to avoid it...
>>
>> At the end of the day, I suppose I am Okay with any of these 3
>> approaches. Original cast, union or this cast you suggest. Jonathan, any
>> preferences on your side?
> 
> Majority of the diff is really about renaming buffer to tx_buffer.
> Could just not bother doing that and instead have buffer and buffer16
> as the two union elements. With msg gone as suggested above, then the diff
> becomes only a few lines and you get to keep the nicety of it being either
> a pair of u8s or a __be16.

I was tempted to try using the spi_write_then_read() - but I suppose 
this may be kind of a hot path.

I'll go with (not)renaming the buffer and dropping the msg, to squeeze 
the diff.

Yours,
	-- Matti

On Mon, 7 Apr 2025 08:23:07 +0300
Matti Vaittinen <mazziesaccount@gmail.com> wrote:

> On 05/04/2025 20:29, Jonathan Cameron wrote:
> > On Thu, 3 Apr 2025 08:16:43 +0300
> > Matti Vaittinen <mazziesaccount@gmail.com> wrote:
> >   
> >> On 03/04/2025 00:04, David Lechner wrote:  
> >>> On 4/2/25 1:09 AM, Matti Vaittinen wrote:  
> >>>> The register data is 12-bit big-endian data. Use be16_to_cpu() to do
> >>>> the conversion, and simple bitwise AND for masking to make it more
> >>>> obvious.
> >>>>
> >>>> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
> >>>> ---
> >>>> Revision history:
> >>>> v1 => v2:
> >>>>    - Fix commit msg to reflect the fact there was no bug
> >>>>    - Drop Fixes tag
> >>>>    - Use union for rx / tx buffer to avoid casting
> >>>>    - Keep the shared message protected by the mutex
> >>>> ---
> >>>>    drivers/iio/adc/ti-adc128s052.c | 18 ++++++++++--------
> >>>>    1 file changed, 10 insertions(+), 8 deletions(-)
> >>>>
> >>>> diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
> >>>> index a456ea78462f..3e69a5fce010 100644
> >>>> --- a/drivers/iio/adc/ti-adc128s052.c
> >>>> +++ b/drivers/iio/adc/ti-adc128s052.c
> >>>> @@ -28,32 +28,34 @@ struct adc128 {
> >>>>    	struct regulator *reg;
> >>>>    	struct mutex lock;
> >>>>    
> >>>> -	u8 buffer[2] __aligned(IIO_DMA_MINALIGN);
> >>>> +	union {
> >>>> +		__be16 rx_buffer;
> >>>> +		u8 tx_buffer[2];  
> > As below. Maybe
> > 		__be16 buffer16;
> > 		u8 buffer[2];  
> 
> Ok.
> 
> >>>> +	} __aligned(IIO_DMA_MINALIGN);
> >>>>    };
> >>>>    
> >>>>    static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
> >>>>    {
> >>>>    	int ret;
> >>>> +	char *msg = &adc->tx_buffer[0];
> >>>>    
> >>>>    	mutex_lock(&adc->lock);
> >>>>    
> >>>> -	adc->buffer[0] = channel << 3;
> >>>> -	adc->buffer[1] = 0;
> >>>> +	msg[0] = channel << 3;
> >>>> +	msg[1] = 0;
> >>>>    
> >>>> -	ret = spi_write(adc->spi, &adc->buffer, 2);
> >>>> +	ret = spi_write(adc->spi, msg, sizeof(adc->tx_buffer));  
> > 
> > I'd get rid of msg as it's now just confusing given we are
> > using the sizeof() here.  
> 
> Ok.
> 
> >>>>    	if (ret < 0) {
> >>>>    		mutex_unlock(&adc->lock);
> >>>>    		return ret;
> >>>>    	}
> >>>>    
> >>>> -	ret = spi_read(adc->spi, &adc->buffer, 2);
> >>>> -
> >>>> +	ret = spi_read(adc->spi, &adc->rx_buffer, 2);  
> > 
> > sizeof(adc->rx_buffer)  
> 
> I was thinking of this but went with raw 2 - because we need to read 
> exactly 2 bytes from the device. Sizeof buffer is matter of software 
> where as the 2 bytes is dictated by the device. (Sure the size of buffer 
> needs to be large enough).
> 
> I don't care it that much though, so I can go with the sizeof() if 
> that's what you prefer. Just explaining that the '2' here was a 
> conscious choice :)

Hmm. If we have a case where we read less than 2 bytes into that buffer
then fair enough.  Otherwise it's correctly sized so having sizeof(buffer)
and having to check that size in only one place is a tiny bit preferable.


> 
> >>>>    	mutex_unlock(&adc->lock);
> >>>> -
> >>>>    	if (ret < 0)
> >>>>    		return ret;
> >>>>    
> >>>> -	return ((adc->buffer[0] << 8 | adc->buffer[1]) & 0xFFF);
> >>>> +	return be16_to_cpu(adc->rx_buffer) & 0xFFF;  
> >>>
> >>>
> >>> The cast isn't exactly beautiful, but this would save a lot of
> >>> lines of diff and a few lines of code by avoiding the need for
> >>> the union and the local msg variable.
> >>>
> >>> 	return be16_to_cpup((__be16 *)adc->buffer) & 0xFFF;  
> > 
> > The cast only works because we have forced the alignment for DMA safety.
> > That to me is a little fragile.
> > 
> > You could do get_unaligned_be16() which doesn't need the cast then carry
> > on using the original buffer.  
> >>
> >> Thanks again for the review David :)
> >>
> >> I am unsure which way to go. I kind of like having the __be16 in the
> >> struct, as it immediately yells "data from device is big-endian". OTOH,
> >> I've never loved unions (and, it silences the above "yelling" quite a
> >> bit). I still think this might be the first time I really see a valid
> >> use-case for an union :) And, you're right this adds more lines,
> >> besides, the cast doesn't look that ugly to me. Yet, I originally had a
> >> cast probably as simple as this (and I also had the __be16 in the
> >> struct), and Jonathan suggested using union to avoid it...
> >>
> >> At the end of the day, I suppose I am Okay with any of these 3
> >> approaches. Original cast, union or this cast you suggest. Jonathan, any
> >> preferences on your side?  
> > 
> > Majority of the diff is really about renaming buffer to tx_buffer.
> > Could just not bother doing that and instead have buffer and buffer16
> > as the two union elements. With msg gone as suggested above, then the diff
> > becomes only a few lines and you get to keep the nicety of it being either
> > a pair of u8s or a __be16.  
> 
> I was tempted to try using the spi_write_then_read() - but I suppose 
> this may be kind of a hot path.

Given it's small, I doubt it would make any noticeable difference in
performance.

> 
> I'll go with (not)renaming the buffer and dropping the msg, to squeeze 
> the diff.

Works for me.

J
> 
> Yours,
> 	-- Matti