Re: [PATCH v2 2/3] platform/x86: wmi: add WMI support to MODULE_DEVICE_TABLE()

[Mattias Jacobsson]

Hi,

On 2019-01-27, Andy Shevchenko wrote:
> On Sun, Jan 27, 2019 at 9:04 PM Mattias Jacobsson <2pi@xxxxxx> wrote:
> >
> > The kernel provides the macro MODULE_DEVICE_TABLE() where driver authors
> > can specify their device type and their array of device_ids and thereby
> > trigger the generation of the appropriate MODULE_ALIAS() output. This is
> > opposed to having to specify one MODULE_ALIAS() for each device. The WMI
> > device type is currently not supported.
> >
> > While using MODULE_DEVICE_TABLE() does increase the complexity as well
> > as spreading out the implementation across the kernel, it does come with
> > some benefits too;
> > * It makes different drivers look more similar; if you can specify the
> >   array of device_ids any device type specific input to MODULE_ALIAS()
> >   will automatically be generated for you.
> > * It helps each driver avoid keeping multiple versions of the same
> >   information in sync. That is, both the array of device_ids and the
> >   potential multitude of MODULE_ALIAS()'s.
> >
> > Add WMI support to MODULE_DEVICE_TABLE() by adding info about struct
> > wmi_device_id in devicetable-offsets.c and add a WMI entry point in
> > file2alias.c.
> >
> > The type argument for MODULE_DEVICE_TABLE(type, name) is wmi.
> 
> > +/* Looks like: wmi:guid */
> > +static int do_wmi_entry(const char *filename, void *symval, char *alias)
> > +{
> > +       DEF_FIELD_ADDR(symval, wmi_device_id, guid_string);
> > +       if (strlen(*guid_string) != WMI_GUID_STRING_LEN) {
> > +               warn("Invalid WMI device id 'wmi:%s' in '%s'\n",
> > +                               *guid_string, filename);
> > +               return 0;
> > +       }
> 
> > +       if (snprintf(alias, 500, WMI_MODULE_PREFIX "%s", *guid_string) < 0) {
> 
> What the point to use snprintf here with arbitrary buffer size if we
> exactly know 2 facts:
> 1. UUID string is  36 characters
> 2. buffer is long enough
> 
> ?

As long as no one changes the code, not much.

> 
> > +               warn("Could not generate all MODULE_ALIAS's in '%s'\n",
> > +                               filename);
> > +               return 0;
> > +       }
> > +       return 1;
> > +}
> 
> -- 
> With Best Regards,
> Andy Shevchenko

Thanks,
Mattias