RE: [PATCH v2 1/4] iio: adc: ltc2309: Introduce chip_info structure

[Jones, Carlos jr]

> On Tue, Mar 24, 2026 at 03:13:28PM +0800, Carlos Jones Jr wrote:
> > Introduce a chip_info structure to facilitate adding support for chip
> > variants with different channel configurations and timing
> > requirements.
> >
> > The chip_info structure contains:
> > - Device name for proper sysfs identification
> > - Channel specifications and count
> > - Read delay timing for variants requiring settling time
> >
> > The ltc2309 struct is modified to store only the read_delay_us value
> > rather than a pointer to the full chip_info, as this is the only
> > runtime-accessed field after probe.
> >
> > This preparatory refactoring does not modify existing LTC2309
> > functionality.
> 
> ...
> > +struct ltc2309_chip_info {
> > +	const char *name;
> > +	unsigned int num_channels;
> > +	const struct iio_chan_spec *channels
> __counted_by_ptr(num_channels);
> > +	unsigned int read_delay_us;
> 
> Now on some architectures this might have gaps. Have you run `pahole`?
> Even if it's fine, I would rather see
> 
> 	const char *name;
> 	const struct iio_chan_spec *channels
> __counted_by_ptr(num_channels);
> 	unsigned int num_channels;
> 	unsigned int read_delay_us;
> 
> OR (if there are limitations of __counted_by_ptr() attribute)
> 
> 	const char *name;
> 	unsigned int read_delay_us;
> 	unsigned int num_channels;
> 	const struct iio_chan_spec *channels
> __counted_by_ptr(num_channels);
> 
> > +};
> ...

Thanks, Andy. The previous arrangement has hole but the latter of the
two recommendations above have none (pahole output shown below).
I will update accordingly.

struct ltc2309_chip_info {
        const char  *              name;                 /*     0     8 */
        unsigned int               read_delay_us;        /*     8     4 */
        unsigned int               num_channels;         /*    12     4 */
        const struct iio_chan_spec  * channels;          /*    16     8 */

        /* size: 24, cachelines: 1, members: 4 */
        /* last cacheline: 24 bytes */
};

Will also revise the static declaration to align with the change.

static const struct ltc2309_chip_info ltc2305_chip_info = {
	.name = "ltc2305",
	.read_delay_us = 2,
	.num_channels = ARRAY_SIZE(ltc2305_channels),
	.channels = ltc2305_channels,
};

And noted on the comments about the alphabetical arrangement
of headers, extra space, and xmas tree order of local variables,
revised as shown below.

static int ltc2309_probe(struct i2c_client *client)
{
	const struct ltc2309_chip_info *chip_info;
	struct iio_dev *indio_dev;
	struct ltc2309 *ltc2309;
	int ret;

Kind regards.