On 27.08.24 11:29, Krzysztof Kozlowski wrote: > On 27/08/2024 11:22, Jan Kiszka wrote: >> On 27.08.24 08:37, Krzysztof Kozlowski wrote: >>> On Mon, Aug 26, 2024 at 11:50:04PM +0200, Jan Kiszka wrote: >>>> From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> >>>> >>>> Describe also the VMAP registers which are needed in order to make use >>>> of the PVU with this PCI host. Furthermore, permit to specify a >>>> restricted DMA pool by phandle. >>> >>> That's an ABI break without explanation why it is necessary. >>> >> >> It is needed in order to support the PVU, as written above. > > Above say only that you want a new feature and that's not really > suitable explanation for ABI break, because answer to this is: add new > feature without breaking existing users. But maybe there is a bug or > something does not work or never work or there are no users, don't know. > >> >> Previous versions of this binding likely didn't consider this use case >> and therefore didn't describe all registers associated with the hardware. >> >> BTW, if you see a way to add the required registers without breaking >> more than needed, I'm all ears. At least the kernel driver will continue >> to work with older DTs when you disable PVU support or do not add a DMA >> pool to the DT. > > If there is no ABI break, because driver still handles correctly old > DTB, then mention it in the commit msg. Well, this is strictly spoken not a topic for this commit because this one should have no clue about what drivers do with DTs according to this binding. But I can put a hint and go into details in the driver patch. Jan -- Siemens AG, Technology Linux Expert Center
