Subject: [PATCH v6 2/4] power: reset: add reboot mode driver

From: [email-masked] (Andy Yan)
Date: Mon, 28 Mar 2016 15:40:29 +0800

Hi Krzysztof :

On 2016?03?28? 14:34, Krzysztof Kozlowski wrote:
> On 24.03.2016 17:03, Andy Yan wrote:
>> Hi Krzystof:
> (...)
>
>>>> +static int get_reboot_mode_magic(struct reboot_mode_driver *reboot,
>>>> +                                const char *cmd)
>>>> +{
>>>> +       const char *normal = "normal";
>>>> +       int magic = 0;
>>>> +       struct mode_info *info;
>>>> +
>>>> +       if (!cmd)
>>>> +               cmd = normal;
>>>> +
>>>> +       list_for_each_entry(info, &reboot->head, list) {
>>>> +               if (!strcmp(info->mode, cmd)) {
>>>> +                       magic = info->magic;
>>>> +                       break;
>>>> +               }
>>>> +       }
>>>> +
>>>> +       return magic;
>>> In absence of 'normal' mode (it is not described as required property)
>>> the magic will be '0'. It would be nice to document that in bindings.
>>> Imagine someone forgets about this and will wonder why 0x0 is written
>>> to his precious register on normal reboot...
>>      If the magic value is '0', we won't touch the register, please see
>> reboot_mode_notify bellow.
> Ah, indeed... so we cannot use value of '0' for magic (e.g. to clear any
> existing value for normal reboot)?

     It seems that the value '0' cannot be used.
>>> It would be nice to document that 'mode-normal' has a special
>>> (hard-coded) meaning.
>>>
>>>> +}
>>>> +
>>>> +static int reboot_mode_notify(struct notifier_block *this,
>>>> +                             unsigned long mode, void *cmd)
>>>> +{
>>>> +       struct reboot_mode_driver *reboot;
>>>> +       int magic;
>>>> +
>>>> +       reboot = container_of(this, struct reboot_mode_driver,
>>>> reboot_notifier);
>>>> +       magic = get_reboot_mode_magic(reboot, cmd);
>>>> +       if (magic)
>>>> +               reboot->write(magic);
>>>> +
>>>> +       return NOTIFY_DONE;
>>>> +}
>>>> +
>>>> +int reboot_mode_register(struct device *dev, int (*write)(int))
>>>> +{
>>>> +       struct reboot_mode_driver *reboot;
>>>> +       struct mode_info *info;
>>>> +       struct property *prop;
>>>> +       size_t len = strlen(PREFIX);
>>>> +       int ret;
>>>> +
>>>> +       reboot = devm_kzalloc(dev, sizeof(*reboot), GFP_KERNEL);
>>>> +       if (!reboot)
>>>> +               return -ENOMEM;
>>>> +
>>>> +       reboot->write = write;
>>>> +       INIT_LIST_HEAD(&reboot->head);
>>>> +       for_each_property_of_node(dev->of_node, prop) {
>>>> +               if (len > strlen(prop->name) || strncmp(prop->name,
>>>> PREFIX, len))
>>>> +                       continue;
>>> New line please for readability.
>>      Okay
>>>> +               info = devm_kzalloc(dev, sizeof(*info), GFP_KERNEL);
>>>> +               if (!info)
>>>> +                       return -ENOMEM;
>>> Ditto.
>>      Okay
>>>> +               strcpy(info->mode, prop->name + len);
>>> Ehm, and how do you protect that name of mode is shorter than 32
>>> characters?
>>      How about info->mode = prop->name + len ?
> I don't get your answer.
> As fair as I read the code, the prop->name can be very long and you are
> copying it from 5 character. If the name of the mode has bazillion
> characters then again my question: how do you protect that it will fit
> in 32 bytes of 'mode'?

     What I mean is set info->mode as a pointer point to prop->name + len

    struct mode_info {
             char *mode;
             ..........
             .........
    }

    info->mode = prop->name + len
>
>>>> +               if (of_property_read_u32(dev->of_node, prop->name,
>>>> &info->magic)) {
>>>> +                       dev_err(dev, "reboot mode %s without magic
>>>> number\n",
>>>> +                               info->mode);
>>>> +                       devm_kfree(dev, info);
>>>> +                       continue;
>>>> +               }
>>>> +               list_add_tail(&info->list, &reboot->head);
>>>> +       }
>>>> +       reboot->reboot_notifier.notifier_call = reboot_mode_notify;
>>>> +       ret = register_reboot_notifier(&reboot->reboot_notifier);
>>>> +       if (ret)
>>>> +               dev_err(dev, "can't register reboot notifier\n");
>>>> +
>>>> +       return ret;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(reboot_mode_register);
>>>> +
>>>> +MODULE_AUTHOR("Andy Yan <[email-masked]");
>>>> +MODULE_DESCRIPTION("System reboot mode driver");
>>>> +MODULE_LICENSE("GPL v2");
>>>> diff --git a/drivers/power/reset/reboot-mode.h
>>>> b/drivers/power/reset/reboot-mode.h
>>>> new file mode 100644
>>>> index 0000000..44ed34f
>>>> --- /dev/null
>>>> +++ b/drivers/power/reset/reboot-mode.h
>>>> @@ -0,0 +1,6 @@
>>>> +#ifndef __REBOOT_MODE_H__
>>>> +#define __REBOOT_MODE_H__
>>>> +
>>>> +int reboot_mode_register(struct device *dev, int (*write)(int));
>>> Documentation would be appreciated. Although it is local header but
>>> you decoupled them and you are exporting the function.
>>      I think I should remove the EXPORT_SYMBOL_GPL.
> You need to export symbols which are located in modules. Is it located
> in module?
>
> Best regards,
> Krzysztof
>
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