From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Likely Subject: Re: RFC: proposal to extend the open-pic interrupt specifier definition Date: Tue, 12 Jan 2010 23:06:10 -0700 Message-ID: References: <9696D7A991D0824DBA8DFAC74A9C5FA30590506E@az33exm25.fsl.freescale.net> <50433.84.105.60.153.1263320254.squirrel@gate.crashing.org> <9696D7A991D0824DBA8DFAC74A9C5FA305988778@az33exm25.fsl.freescale.net> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <9696D7A991D0824DBA8DFAC74A9C5FA305988778-ofAVchDyotYzzZk0BCvKg5jmvxFtTJ+o0e7PPNI6Mm0@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org To: Yoder Stuart-B08248 Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, parch-QRwYI7m9GJLYtjvyW6yDsg@public.gmane.org List-Id: devicetree@vger.kernel.org On Tue, Jan 12, 2010 at 11:36 AM, Yoder Stuart-B08248 wrote: >> > The advantage of the above approach is backwards compatibility. >> > Existing interrupt specifiers (and device trees) are valid with >> > this proposal. >> >> Actually they're not, like BenH pointed out. > > The proposal is backwards compatible. =A0An existing interrupt > specifier =A0(e.g. interrupts =3D <24 2>;) retains its exact > same meaning. =A0Old device trees do not need to change > to comply with the proposal. You also need to deal with the case of old drivers incorrectly binding to and trying to understand the new data. > I'm not directly familiar with the case Ben pointed out, but > it sounded like Apple used the 1st cell in some non-standard > way. > > It is true that openpic drivers would need to change to handle > the new specifier-- minimally masking the level/sense field > to 2 bits. Which makes the new binding incompatible with old kernels/drivers which just leads to confusion. It's not worth toying with. Just create a new compatible value for this new binding and be done with it. When a driver gets modified to handle the new behaviour, then it can be also changed to bind against the new compatible value too. g. -- = Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd.