linux-kernel - Re: [PATCH, v1 1/1] gpio: aspeed: Add gpio base address reading

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Message-Id: <775b31f0-c74c-4ebe-9588-bca3ee423383@www.fastmail.com>
Date:   Thu, 14 Jan 2021 10:57:13 +1030
From:   "Andrew Jeffery" <andrew@...id.au>
To:     "Hongwei Zhang" <hongweiz@....com>,
        "Linus Walleij" <linus.walleij@...aro.org>,
        "Bartosz Golaszewski" <bgolaszewski@...libre.com>,
        "Joel Stanley" <joel@....id.au>, linux-gpio@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        openbmc@...ts.ozlabs.org
Subject: Re: [PATCH, v1 1/1] gpio: aspeed: Add gpio base address reading

Hello,

On Thu, 14 Jan 2021, at 09:08, Hongwei Zhang wrote:
> Add gpio base address reading in the driver; in old code, it just
> returns -1 to gpio->chip.base.

Why do you want to do this? It feels hacky. The base address only affects the 
legacy sysfs number-space, and even then if you're using the sysfs interface 
you can discover the base address for a specific gpiochip via the associated 
attribute. For example:

# cat /sys/bus/platform/devices/1e780000.gpio/gpio/gpiochip*/base
816

I feel that you should instead be changing your userspace not to assume a fixed 
value.

Finally, the base value is a linux-specific thing and doesn't belong in the 
devicetree, and if it did, you would also need to update the devicetree binding 
in Documentation/.

Cheers,

Andrew