Re: [PATCH v2 2/2] asus-wmi: Add support for ROG X13 tablet mode

[Luke Jones]

On Tue, Aug 9 2022 at 09:12:37 +0200, Andy Shevchenko 
<andy.shevchenko@xxxxxxxxx> wrote:
> On Tue, Aug 9, 2022 at 5:26 AM Luke Jones <luke@xxxxxxxxxx> wrote:
>
> ...
>
> >  >>  +                       pr_err("This device has lid-flip-rog 
> > quirk
> >  >> but got ENODEV checking it. This is a bug.");
> >  >
> >  > dev_err() ?
> >
> >  Okay, changed here and in previous patch to match it.
> >
> >  So that I'm clearer on dev_err(), this doesn't do something like 
> > exit
> >  the module does it? It's just a more detailed error print?
>
> Yes, it's more specific when the user sees it. The pr_err() is global
> and anonymous (you can only point to the driver, and not the instance
> of the device bound to it), while dev_err() is device specific and the
> user will immediately see which device instance is failing. Yet it's
> not a problem for this particular driver, because I don't believe one
> may have two, but it's a good coding practice in general.
>
> (Note the last sentence: "good coding practice")
>
> ...
>
> >  >>  +static void lid_flip_rog_tablet_mode_get_state(struct asus_wmi
> >  >> *asus)
> >  >>  +{
> >  >>  +       int result = asus_wmi_get_devstate_simple(asus,
> >  >> ASUS_WMI_DEVID_LID_FLIP_ROG);
> >  >>  +
> >  >>  +       if (result >= 0) {
> >  >
> >  > First of all, it's better to decouple assignment and definition, 
> > and
> >  > move assignment closer to its user. This is usual pattern.
> >
> >  I don't fully understand why you would want the separation given how
> >  short these two blocks are (I'll change in this and previous patch 
> > of
> >  course, I just don't personally understand it).
>
> See above, "good coding practice". Why?
>
> Imagine your code to be in hypothetical v5.10:
>
>   int x = foo(param1, param2, ...);
>
>   if (x)
>     return Y;
>
>
> Now, at v5.12 somebody adds a new feature which touches your code:
>
>   int x = foo(param1, param2, ...);
>   struct bar *baz;
>
>   if (we_have_such_feature_disabled)
>     return Z;
>
>   if (x)
>     return Y;
>
>   baz = ...
>
> And then somebody else in v5.13 does another feature:
>
>   int x = foo(param1, param2, ...);
>   struct bar *baz;
>
>   if (we_have_such_feature_disabled)
>     return Z;
>
>   /* parameter 1 can be NULL, check it */
>   if (!param1)
>     return -EINVAL;
>
>   if (x)
>     return Y;
>
>   baz = ...
>
> Do you see now an issue? If you emulate this as a sequence of Git
> changes the last one is easily missing subtle detail. That's why "good
> coding practice".
>
> --
> With Best Regards,
> Andy Shevchenko

That's a great example! Thanks mate, really appreciate it.