From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Subject: Re: [PATCH v2] device property: Get rid of union aliasing Date: Mon, 14 May 2018 19:13:24 +0300 Message-ID: References: <20180508131547.44366-1-andriy.shevchenko@linux.intel.com> <20180514121817.GA27869@wunner.de> <20180514154017.GA6734@wunner.de> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180514154017.GA6734@wunner.de> Sender: linux-kernel-owner@vger.kernel.org To: Lukas Wunner Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Ard Biesheuvel , linux-efi@vger.kernel.org, Sakari Ailus , Mika Westerberg , "Rafael J . Wysocki" , ACPI Devel Maling List List-Id: linux-acpi@vger.kernel.org On Mon, 2018-05-14 at 17:40 +0200, Lukas Wunner wrote: > On Mon, May 14, 2018 at 03:48:09PM +0300, Andy Shevchenko wrote: > > On Mon, 2018-05-14 at 14:18 +0200, Lukas Wunner wrote: > > > On Tue, May 08, 2018 at 04:15:47PM +0300, Andy Shevchenko wrote: > > > > --- a/drivers/firmware/efi/apple-properties.c > > > > +++ b/drivers/firmware/efi/apple-properties.c > > > > @@ -13,6 +13,9 @@ > > > > + * FIXME: The approach is still based on union aliasing and > > > > should be > > > > + * replaced by a proper resource provider. > > > > > > Why? All Apple EFI properties are either boolean or u8 arrays. > > > You've correctly changed this file to always supply u8 arrays, > > > so I don't see where union aliasing is happening here? > > > > Okay, for now I can see only Thunderbolt user of these properties > > (is it > > correct?) in upstream which uses u8 arrays indeed. > > That is correct, thunderbolt.ko is so far the only user. > > > > Though the implementation is quite fragile in this sense, because it > > doesn't discourage people to use device_property_read_string() in > > case > > when it's indeed a string (I saw these kind of properties in the > > very > > dump you posted on your GH page). > > Well if that is your concern then you need to prevent functions which > retrieve properties to use the wrong type. > > E.g. to prevent retrieval of the u8 array as string, you'd have to > amend drivers/base/property.c:pset_prop_read_string_array() to > check the type of the property found and return -EINVAL if it's not > string. I think it's doable. I will hack a new version later this week. But it still not a (best) solution for Apple properties. B/c as I told already I saw in _your_ dump the _string_ properties. Someone might have got an idea to use them as _strings_. -- Andy Shevchenko Intel Finland Oy