Re: [PATCH master 2/7] nvmem: bsec: correct regmap's max_register

[Robin van der Gracht <robin@protonic.nl>]

Hi Ahmad,

Comments are below.

On Tue,  2 Jan 2024 18:00:55 +0100
Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:

> The max_register must be a multiple of the register stride, which is not
> the case for (384 / 4) - 1 == 95. Instead, we should be setting 380, so
> fix the calculation to do this.
> 
> Fixes: 094ce0ee7cdf ("nvmem: bsec: correct regmap's max_register")
> Reported-by: Robin van der Gracht <robin@protonic.nl>
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  drivers/nvmem/bsec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/nvmem/bsec.c b/drivers/nvmem/bsec.c
> index 889f14428d59..22e30c6c2e82 100644
> --- a/drivers/nvmem/bsec.c
> +++ b/drivers/nvmem/bsec.c
> @@ -218,7 +218,7 @@ static int stm32_bsec_probe(struct device *dev)
>  	priv->map_config.reg_bits = 32;
>  	priv->map_config.val_bits = 32;
>  	priv->map_config.reg_stride = 4;
> -	priv->map_config.max_register = (data->size / 4) - 1;
> +	priv->map_config.max_register = data->size - priv->map_config.reg_stride;
>  
>  	priv->lower = data->lower;
>  

This patch gives a bsec device size of 1520 bytes. Which means I'm now
allowed to read/write beyond register 95 without an error.

barebox@board:/ ls -l /dev/stm32-bsec
crw-------           1520 /dev/stm32-bsec

The device size is now in bytes, but the read/write offsets given to
the md and mw commands is still in bytes/stride.

I.e. to read register 95:
md -l -s /dev/stm32-bsec 380+4 
0000017c: xxxxxxxx

I can now also read register 100:
md -l -s /dev/stm32-bsec 400+4 
00000190: 00000000                                           ....

This doesn't seem right.

max_register should probably stay 95. See doc[1]

1:https://git.pengutronix.de/cgit/barebox/tree/include/linux/regmap.h?h=v2023.12.0#n33

Robin