Re: gpio: gpio-pci-idio-16 regression after LTS upgrade

[William Breathitt Gray <wbg@kernel.org>]

On Mon, Oct 06, 2025 at 09:37:14AM +0100, Mark Cave-Ayland wrote:
> After some more debugging I was able to determine that the failure was
> due to the regmap cache failing initialisation in
> drivers/base/regmap/regcache-flat.c::regcache_flat_init() because
> max_register wasn't set on the regmap. I was able to fix that fairly
> easily with this:
> 
> 
> diff --git a/drivers/gpio/gpio-pci-idio-16.c
> b/drivers/gpio/gpio-pci-idio-16.c
> index 44c0a21b1d1d..55be571b5cca 100644
> --- a/drivers/gpio/gpio-pci-idio-16.c
> +++ b/drivers/gpio/gpio-pci-idio-16.c
> @@ -41,6 +41,7 @@ static const struct regmap_config
> idio_16_regmap_config = {
>          .reg_stride = 1,
>          .val_bits = 8,
>          .io_port = true,
> +  .max_register = 0x7,
>          .wr_table = &idio_16_wr_table,
>          .rd_table = &idio_16_rd_table,
>          .volatile_table = &idio_16_rd_table,

This particular failure is separate from the get_direction issue
discovered after. It would be good to have this fix as its own patch so
we can keep each solution dedicated to their respective failures and
streamline any necessary backports to the stable trees.

I have some travel scheduled in the next couple days, but I can
probably get a patch series addressing both issues ready by the end of
the week. I'll also CC the stable mailing list so we can get the fixes
picked up for the LTS kernel they are affecting.

William Breathitt Gray