linux-kernel - Re: [PATCH] lib/logic_pio: Fix overlap check for pio registery

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Date:   Fri, 18 Dec 2020 10:40:13 +0000
From:   John Garry <john.garry@...wei.com>
To:     Jiahui Cen <cenjiahui@...wei.com>, <linux-kernel@...r.kernel.org>
CC:     Wei Xu <xuwei5@...ilicon.com>, Arnd Bergmann <arnd@...db.de>,
        "Bjorn Helgaas" <bhelgaas@...gle.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        <xieyingtai@...wei.com>
Subject: Re: [PATCH] lib/logic_pio: Fix overlap check for pio registery

On 18/12/2020 06:23, Jiahui Cen wrote:
> Since the [start, end) is a half-open interval, a range with the end equal
> to the start of another range should not be considered as overlapped.
> 
> Signed-off-by: Jiahui Cen <cenjiahui@...wei.com>
> ---
>   lib/logic_pio.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/logic_pio.c b/lib/logic_pio.c
> index f32fe481b492..445d611f1dc1 100644
> --- a/lib/logic_pio.c
> +++ b/lib/logic_pio.c
> @@ -57,7 +57,7 @@ int logic_pio_register_range(struct logic_pio_hwaddr *new_range)
>   		    new_range->flags == LOGIC_PIO_CPU_MMIO) {
>   			/* for MMIO ranges we need to check for overlap */
>   			if (start >= range->hw_start + range->size ||
> -			    end < range->hw_start) {
> +			    end <= range->hw_start) {

It looks like your change is correct, but should not really have an 
impact in practice since:
a: BIOSes generally list ascending IO port CPU addresses
b. there is space between IO port CPU address regions

Have you seen a problem here?

Thanks,
John