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

[Andy Yan]

Hi Krzysztof :

On 2016å03æ28æ 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 <andy.yan@xxxxxxxxxxxxxx");
> > > > +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