linux-kernel - Re: [PATCH] gpio: omap: use dynamic allocation of base

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Message-ID: <CACRpkdauDEys-XyYvb=jt1U6FcKc-qiie-A3W0WQ08rnm42DwQ@mail.gmail.com>
Date:   Mon, 16 Jan 2023 15:24:42 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Andreas Kemnade <andreas@...nade.info>
Cc:     grygorii.strashko@...com, ssantosh@...nel.org, khilman@...nel.org,
        brgl@...ev.pl, linux-omap@...r.kernel.org,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpio: omap: use dynamic allocation of base

On Fri, Jan 13, 2023 at 9:59 PM Andreas Kemnade <andreas@...nade.info> wrote:

> Static allocatin is deprecated and may cause probe mess,
> if probe order is unusual.
>
> like this example
> [    2.553833] twl4030_gpio twl4030-gpio: gpio (irq 145) chaining IRQs 161..178
> [    2.561401] gpiochip_find_base: found new base at 160
> [    2.564392] gpio gpiochip5: (twl4030): added GPIO chardev (254:5)
> [    2.564544] gpio gpiochip5: registered GPIOs 160 to 177 on twl4030
> [...]
> [    2.692169] omap-gpmc 6e000000.gpmc: GPMC revision 5.0
> [    2.697357] gpmc_mem_init: disabling cs 0 mapped at 0x0-0x1000000
> [    2.703643] gpiochip_find_base: found new base at 178
> [    2.704376] gpio gpiochip6: (omap-gpmc): added GPIO chardev (254:6)
> [    2.704589] gpio gpiochip6: registered GPIOs 178 to 181 on omap-gpmc
> [...]
> [    2.840393] gpio gpiochip7: Static allocation of GPIO base is deprecated, use dynamic allocation.
> [    2.849365] gpio gpiochip7: (gpio-160-191): GPIO integer space overlap, cannot add chip
> [    2.857513] gpiochip_add_data_with_key: GPIOs 160..191 (gpio-160-191) failed to register, -16
> [    2.866149] omap_gpio 48310000.gpio: error -EBUSY: Could not register gpio chip
>
> So probing was done in an unusual order, causing mess
> and chips not getting their gpio in the end.
>
> Signed-off-by: Andreas Kemnade <andreas@...nade.info>

Dangerous but beautiful change. Let's be brave.
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

> maybe CC stable? not sure about good fixes tag.

I wouldn't do that from the outset. If there are no problems
for a few kernel releases we can think about doing that.

Yours,
Linus Walleij