Re: [PATCH] platform/x86: thinkpad_acpi: Prefer struct_size over open coded arithmetic
From: Greg KH
Date: Sat Sep 25 2021 - 07:23:17 EST
On Sat, Sep 25, 2021 at 12:40:44PM +0200, Len Baker wrote:
> On Tue, Sep 21, 2021 at 05:15:35PM +0200, Greg KH wrote:
> > First off, why is a single driver doing so many odd things with
> > attribute groups? Why not just use them the way that the rest of the
> > kernel does? Why does this driver need this special handling and no one
> > else does?
> Is  the correct way to deal with devices attributes? I think so.
>  https://www.kernel.org/doc/html/latest/driver-api/driver-model/driver.html#attributes
No, do not use driver_create_file(), see:
as a more up to date thing.
Someone should fix that in-kernel documentation one day :)
> > I think the default way of handling if an attribute is enabled or not,
> > should suffice here, and make things much simpler overall as all of this
> > crazy attribute handling can just be removed.
> Sorry but what is the default way? Would it be correct to check if the
> file exists?
Use the is_visable() callback for the attribute group to enable/disable
the creation of the sysfs file.
> > Bonus would also be that I think it would fix the race conditions that
> > happen when trying to create attributes after the device is bound to the
> > driver that I think the existing driver has today.
> > > > (I see the caller uses +2? Why? It seems to be using each of hotkey_attributes,
> > > > plus 1 more attr, plus a final NULL?)
> > >
> > > The +2 is actually for 2 extra attributes (making the total number
> > > of extra attributes +3 because the sizeof(struct attribute_set_obj)
> > > already includes 1 extra).
> > >
> > > FWIW these 2 extra attributes are for devices with a
> > > a physical rfkill on/off switch and for the device being
> > > a convertible capable of reporting laptop- vs tablet-mode.
> > Again, using the default way to show (or not show) attributes should
> > solve this issue. Why not just use that instead?
> What is the default way? Would it be correct to use device_create_file()
> and device_remove_file()?
Put all the attributes into an attribute group and attach it to the
driver. The driver core will create/remove the files when needed. The
link above should help explain that a bit better, and I can point you at
examples if needed.
Does that help?