linux-kernel - Re: [RESEND PATCH v3 1/2] of: base: Introduce of_alias_get_alias

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Date:   Thu, 27 Sep 2018 09:19:46 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Michal Simek <michal.simek@...inx.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Michal Simek <monstr@...str.eu>,
        Greg KH <gregkh@...uxfoundation.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Subject: Re: [RESEND PATCH v3 1/2] of: base: Introduce of_alias_get_alias_list()
 to check alias IDs

Hi Michal,

On Wed, Sep 26, 2018 at 1:01 PM Michal Simek <michal.simek@...inx.com> wrote:
> On 24.9.2018 09:41, Geert Uytterhoeven wrote:
> > On Thu, Sep 20, 2018 at 1:42 PM Michal Simek <michal.simek@...inx.com> wrote:
> >> The function travels the lookup table to record alias ids for the given
> >> device match structures and alias stem.
> >> This function will be used by serial drivers to check if requested alias
> >> is allocated or free to use.
> >>
> >> Signed-off-by: Michal Simek <michal.simek@...inx.com>
> >> Reviewed-by: Rob Herring <robh@...nel.org>
> >
> > I know this has already been applied, it just drew my attention.
> >
> >> --- a/drivers/of/base.c
> >> +++ b/drivers/of/base.c
> >> @@ -16,6 +16,7 @@
> >>
> >>  #define pr_fmt(fmt)    "OF: " fmt
> >>
> >> +#include <linux/bitmap.h>
> >>  #include <linux/console.h>
> >>  #include <linux/ctype.h>
> >>  #include <linux/cpu.h>
> >> @@ -1943,6 +1944,57 @@ int of_alias_get_id(struct device_node *np, const char *stem)
> >>  EXPORT_SYMBOL_GPL(of_alias_get_id);
> >>
> >>  /**
> >> + * of_alias_get_alias_list - Get alias list for the given device driver
> >> + * @matches:   Array of OF device match structures to search in
> >> + * @stem:      Alias stem of the given device_node
> >> + * @bitmap:    Bitmap field pointer
> >> + * @nbits:     Maximum number of alias ID which can be recorded it bitmap
> >
> > IDs
> >
> >> + *
> >> + * The function travels the lookup table to record alias ids for the given
> >> + * device match structures and alias stem.
> >> + *
> >> + * Return:     0 or -ENOSYS when !CONFIG_OF
> >> + */
> >> +int of_alias_get_alias_list(const struct of_device_id *matches,
> >> +                            const char *stem, unsigned long *bitmap,
> >> +                            unsigned int nbits)
> >> +{
> >> +       struct alias_prop *app;
> >> +
> >> +       /* Zero bitmap field to make sure that all the time it is clean */
> >> +       bitmap_zero(bitmap, nbits);
> >> +
> >> +       mutex_lock(&of_mutex);
> >> +       pr_debug("%s: Looking for stem: %s\n", __func__, stem);
> >> +       list_for_each_entry(app, &aliases_lookup, link) {
> >> +               pr_debug("%s: stem: %s, id: %d\n",
> >> +                        __func__, app->stem, app->id);
> >> +
> >> +               if (strcmp(app->stem, stem) != 0) {
> >> +                       pr_debug("%s: stem comparison doesn't passed %s\n",
> >
> > didn't pass?
> >
> >> +                                __func__, app->stem);
> >> +                       continue;
> >> +               }
> >> +
> >> +               if (app->id >= nbits) {
> >> +                       pr_debug("%s: ID %d greater then bitmap field %d\n",
> >
> > than
> > %u for unsigned int
>
> I won't fix this now because this can be done together with one change
> described below.
>
> >
> >> +                               __func__, app->id, nbits);
> >> +                       continue;
> >
> > Shouldn't this return an error, if of_match_node() below would have matched?
>
> IIRC Above check is for "serial" name.
> This one is for getting XX number from alias "serialXX".
> And below is checking compatible string.
>
> You are calling this function from uartps with 32 lines limit and there
> is serial33 alias poiting to uartlite (for example) then you don't want
> to break this call for that.
>
> What can be done is that compatible string is checked first and if this
> passed then ids are check and error can be returned or bit sets.

That's what I meant: currently any serialN with N >= nbits is ignored, even
if the alias applies to the driver that called the function.

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