Re: [PATCH v3 3/6] spi: expand device name to include all CS lines for multi-CS devices

[Nuno Sá]

On 2026-08-18 09:45:05+03:00, Andy Shevchenko wrote:
> On Mon, Aug 17, 2026 at 08:32:57PM -0300, Jonathan Santos wrote:
> 
> > The device name for SPI devices was formatted as <controller>.<cs0>,
> > always using only the first chip-select index, ignoring the remaining CS
> > lines.
> > 
> > Change the naming format to <controller>.<cs0>+<cs1>+... so that all
> > active chip-selects are reflected in the device name. Single-CS devices
> > are not affected since the loop only appends extra indices when
> > num_chipselect is greater than one.
> 
> ...
> 
> > -	dev_set_name(&spi->dev, "%s.%u", dev_name(&spi->controller->dev),
> > -		     spi_get_chipselect(spi, 0));
> > +	cs_len = scnprintf(cs_str, sizeof(cs_str), "%u", spi_get_chipselect(spi, 0));
> > +	for (unsigned int idx = 1; idx < spi->num_chipselect; idx++)
> > +		cs_len += scnprintf(cs_str + cs_len, sizeof(cs_str) - cs_len,
> > +				    "+%u", spi_get_chipselect(spi, idx));
> 
> So, if this won't support sparse CS list, I would just go with a standard range:
> 
> 	dev_set_name(&spi->dev, "%s.%u-%u", dev_name(&spi->controller->dev),
> 		     spi_get_chipselect(spi, 0), spi_get_chipselect(spi, 0) + spi->num_chipselect - 1);
> 

I don't think there's anything forcing cs to be contiguous. So cs4-0 does
not mean we have 0,1,2,3 and 4 which I think the above implies.

Moreover, i also don't think is guaranteed that `spi_get_chipselect(spi,
0) + spi->num_chipselect - 1)` yields a valid cs. IOW, in theory

spi_get_chipselect(spi, spi->num_chipselect - 1) might be different
than spi_get_chipselect(spi, 0) + spi->num_chipselect - 1

- Nuno Sá

> (yes, need a variation for num_chipselect == 1, but I leave the rest for you)
> 
> Note, I do not see that we are expecting to see the sparse CS list here. It
> would make too complex logic to follow. So, range approach is KISS in my opinion.