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

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Message-ID: <56c81d1a-e2f8-067e-4908-686cd83d478c@xilinx.com>
Date:   Thu, 27 Sep 2018 09:22:55 +0200
From:   Michal Simek <michal.simek@...inx.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        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

On 27.9.2018 09:19, Geert Uytterhoeven wrote:
> 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.

ok. Let me create a patch and check compatible string first and then
setup bit or fail if N >= nbits.

Thanks,
Michal