linux-kernel - Re: [PATCH v2 2/2] driver core: add helper for deferred probe reason setting

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Date:   Fri, 19 Mar 2021 12:46:10 +0100
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] driver core: add helper for deferred probe reason
 setting

On 19.03.21 12:13, Andy Shevchenko wrote:
> On Fri, Mar 19, 2021 at 1:05 PM Ahmad Fatoum <a.fatoum@...gutronix.de> wrote:
>>
>> We now have three places within the same file doing the same operation
>> of freeing this pointer and setting it anew. A helper make this
> 
> makes
> 
>> arguably easier to read, so add one.
> 
> FWIW,
> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

Thanks will add for v3.

> Now I'm wondering why deferred_probe_reason is not defined with const.
> 
> Can you check and maybe squeeze a patch in the middle (before these
> two of this series) to move to const?

The deferred_probe_reason is only used in this file and it either holds
NULL or a pointer to a dynamically allocated string. I don't see a reason
why the member should be const.

Cheers,
Ahmad

>> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
>> ---
>> v1 -> v2:
>>  - no change
>> ---
>>  drivers/base/dd.c | 17 +++++++++++------
>>  1 file changed, 11 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
>> index e2cf3b29123e..4201baa1cc13 100644
>> --- a/drivers/base/dd.c
>> +++ b/drivers/base/dd.c
>> @@ -69,6 +69,12 @@ static char async_probe_drv_names[ASYNC_DRV_NAMES_MAX_LEN];
>>   */
>>  static bool defer_all_probes;
>>
>> +static void __device_set_deferred_probe_reason(const struct device *dev, char *reason)
>> +{
>> +       kfree(dev->p->deferred_probe_reason);
>> +       dev->p->deferred_probe_reason = reason;
>> +}
>> +
>>  /*
>>   * deferred_probe_work_func() - Retry probing devices in the active list.
>>   */
>> @@ -97,8 +103,7 @@ static void deferred_probe_work_func(struct work_struct *work)
>>
>>                 get_device(dev);
>>
>> -               kfree(dev->p->deferred_probe_reason);
>> -               dev->p->deferred_probe_reason = NULL;
>> +               __device_set_deferred_probe_reason(dev, NULL);
>>
>>                 /*
>>                  * Drop the mutex while probing each device; the probe path may
>> @@ -140,8 +145,7 @@ void driver_deferred_probe_del(struct device *dev)
>>         if (!list_empty(&dev->p->deferred_probe)) {
>>                 dev_dbg(dev, "Removed from deferred list\n");
>>                 list_del_init(&dev->p->deferred_probe);
>> -               kfree(dev->p->deferred_probe_reason);
>> -               dev->p->deferred_probe_reason = NULL;
>> +               __device_set_deferred_probe_reason(dev, NULL);
>>         }
>>         mutex_unlock(&deferred_probe_mutex);
>>  }
>> @@ -220,11 +224,12 @@ void device_unblock_probing(void)
>>  void device_set_deferred_probe_reason(const struct device *dev, struct va_format *vaf)
>>  {
>>         const char *drv = dev_driver_string(dev);
>> +       char *reason;
>>
>>         mutex_lock(&deferred_probe_mutex);
>>
>> -       kfree(dev->p->deferred_probe_reason);
>> -       dev->p->deferred_probe_reason = kasprintf(GFP_KERNEL, "%s: %pV", drv, vaf);
>> +       reason = kasprintf(GFP_KERNEL, "%s: %pV", drv, vaf);
>> +       __device_set_deferred_probe_reason(dev, reason);
>>
>>         mutex_unlock(&deferred_probe_mutex);
>>  }
>> --
>> 2.29.2
>>
> 
> 

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