Re: [PATCH] iio: adc: ti-ads7950: use spi_optimize_message()

[David Lechner]

On 4/14/26 4:54 AM, Andy Shevchenko wrote:
> On Sat, Apr 11, 2026 at 05:13:33PM -0500, David Lechner wrote:
>> Use spi_optimize_message() to reduce CPU usage during buffered reads.
>>
>> On hardware with support for SPI_CS_WORD, this reduced the CPU usage
>> of the threaded interrupt by about 5%. On hardware without support, this
>> should reduce CPU usage even more since it won't have to split the SPI
>> transfers each time the interrupt handler is called.
>>
>> The update_scan_mode callback hand to be moved to the buffer preenable

s/hand/had/

>> callback since the SPI transfer mode can't be changed after
>> spi_optimize_message() has been called. (The buffer postenable callback
>> can't be used because it happens after the trigger is enabled, so the
>> SPI message needs to be optimized before that.)
>>
>> The indent of ti_ads7950_read_raw is changed since there is no longer
>> anything else in the struct to align with since we removed
>> ti_ads7950_update_scan_mode.
> 
> Some of the func() are mentioned w/o parentheses and I got lost which one is
> which. Also callbacks usually mentioned as .callback() (with a leading dot).

I didn't put () in the last paragraph because I was talking about the function
pointer, not the function. I guess I missed update_scan_mode() though.

> 
> The second paragraph doesn't tell me clearly if there is a behaviour change
> from user perspective.
> 

It is not clear that the difference the user can notice is that there are
some CPU cycles freed up for other tasks?