Re: [PATCH] gpio: gpio-pca953x: no interrupts with 4-bit devices

[Alexander Stein <alexander.stein@xxxxxxxxxxxxxxxxxxxxx>]

On Wednesday 09 March 2016 12:37:09, mrpace2@xxxxxxxxx wrote:
> I/O expanders with less than 8 I/O (PCA9536 and PCA9537, currently) fail 
> to invoke interrupt handlers because the NBANK macro
> 
>      #define NBANK(chip) (chip->gpio_chip.ngpio / BANK_SZ)
> incorrectly calculates no banks for these devices. As a result, 
> pca953x_irq_pending() never sets the trigger_seen flag.
> 
> The patch below fixed the issue by changing the NBANK() macro.
> 
> Signed-off-by: Frank Edelhaeuser <mrpace2 <at> gmail.com>
> ---
> diff -Nur a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
> --- a/drivers/gpio/gpio-pca953x.c 2016-03-08 00:00:00.000000000 +0000
> +++ b/drivers/gpio/gpio-pca953x.c 2016-03-08 00:00:00.000000000 +0000
> @@ -86,7 +86,7 @@
>   #define MAX_BANK 5
>   #define BANK_SZ 8
> 
> -#define NBANK(chip) (chip->gpio_chip.ngpio / BANK_SZ)
> +#define NBANK(chip) (((chip->gpio_chip.ngpio - 1) / BANK_SZ) + 1)

If ngpio is 0 (e.g. wrong platform device) this underflows and gets a completly wrong result. But I see more of those "ngpio - 1" all over the place.
What about?
> #define NBANK(chip) (((chip->gpio_chip.ngpio + (BANK_SZ - 1)) / BANK_SZ))

Best regards,
Alexander

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