linux-kernel - Re: [RFC v1 PATCH 1/3] drivers: soc: add support for soc_device_match returning -EPROBE

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Message-ID: <CAMuHMdUbrPxtJ9DCP0_nFrReuuO4vFY2J79LrKY82D7bCOfzRw@mail.gmail.com>
Date:   Mon, 19 Apr 2021 10:20:13 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Alice Guo (OSS)" <alice.guo@....nxp.com>
Cc:     gregkh@...uxfoundation.org, rafael@...nel.org,
        horia.geanta@....com, aymen.sghaier@....com,
        herbert@...dor.apana.org.au, davem@...emloft.net, tony@...mide.com,
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        Arnd Bergmann <arnd@...db.de>
Subject: Re: [RFC v1 PATCH 1/3] drivers: soc: add support for soc_device_match
 returning -EPROBE_DEFER

Hi Alice,

CC Arnd (soc_device_match() author)

On Mon, Apr 19, 2021 at 6:28 AM Alice Guo (OSS) <alice.guo@....nxp.com> wrote:
> From: Alice Guo <alice.guo@....com>
>
> In i.MX8M boards, the registration of SoC device is later than caam
> driver which needs it. Caam driver needs soc_device_match to provide
> -EPROBE_DEFER when no SoC device is registered and no
> early_soc_dev_attr.

I'm wondering if this is really a good idea: soc_device_match() is a
last-resort low-level check, and IMHO should be made available early on,
so there is no need for -EPROBE_DEFER.

>
> Signed-off-by: Alice Guo <alice.guo@....com>

Thanks for your patch!

> --- a/drivers/base/soc.c
> +++ b/drivers/base/soc.c
> @@ -110,6 +110,7 @@ static void soc_release(struct device *dev)
>  }
>
>  static struct soc_device_attribute *early_soc_dev_attr;
> +static bool soc_dev_attr_init_done = false;

Do you need this variable?

>
>  struct soc_device *soc_device_register(struct soc_device_attribute *soc_dev_attr)
>  {
> @@ -157,6 +158,7 @@ struct soc_device *soc_device_register(struct soc_device_attribute *soc_dev_attr
>                 return ERR_PTR(ret);
>         }
>
> +       soc_dev_attr_init_done = true;
>         return soc_dev;
>
>  out3:
> @@ -246,6 +248,9 @@ const struct soc_device_attribute *soc_device_match(
>         if (!matches)
>                 return NULL;
>
> +       if (!soc_dev_attr_init_done && !early_soc_dev_attr)

if (!soc_bus_type.p && !early_soc_dev_attr)

> +               return ERR_PTR(-EPROBE_DEFER);
> +
>         while (!ret) {
>                 if (!(matches->machine || matches->family ||
>                       matches->revision || matches->soc_id))

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds