On 19/09/2022 01:12, Doug Berger wrote: > On 9/18/2022 3:31 AM, Krzysztof Kozlowski wrote: >> On 14/09/2022 18:13, Doug Berger wrote: >>> On 9/14/2022 7:55 AM, Rob Herring wrote: >>>> On Tue, Sep 13, 2022 at 12:55:03PM -0700, Doug Berger wrote: >>>>> Introduce designated-movable-block.yaml to document the >>>>> devicetree binding for Designated Movable Block children of the >>>>> reserved-memory node. >>>> >>>> What is a Designated Movable Block? This patch needs to stand on its >>>> own. >>> As noted in my reply to your [PATCH 00/21] comment, my intention in >>> submitting the entire patch set (and specifically PATCH 00/21]) was to >>> communicate this context. Now that I believe I understand that only this >>> patch should have been submitted to the devicetree-spec mailing list, I >>> will strive harder to make it more self contained. >> >> The submission of entire thread was ok. What is missing is the >> explanation in this commit. This commit must be self-explanatory (e.g. >> in explaining "Why are you doing it?"), not rely on other commits for >> such explanation. >> >>> >>>> >>>> Why does this belong or need to be in DT? >>> While my preferred method of declaring Designated Movable Blocks is >>> through the movablecore kernel parameter, I can conceive that others may >>> wish to take advantage of the reserved-memory DT nodes. In particular, >>> it has the advantage that a device can claim ownership of the >>> reserved-memory via device tree, which is something that has yet to be >>> implemented for DMBs defined with movablecore. >> >> Rephrasing the question: why OS memory layout and OS behavior is a >> property of hardware (DTS)? > I would say the premise is fundamentally the same as the existing > reserved-memory child node. I don't think it is fundamentally the same. The existing reserved-memory node describes memory used by hardware - by other devices. The OS way of handling this memory - movable, reclaimable etc - is not part of it. So no, it is not the same. > > I've been rethinking how this should be specified. I am now thinking > that it may be better to introduce a new Reserved Memory property that > serves as a modifier to the 'reusable' property. The 'reusable' property > allows the OS to use memory that has been reserved for a device and > therefore requires the device driver to reclaim the memory prior to its > use. However, an OS may have multiple ways of implementing such reuse > and reclamation. ... and I repeat the question - why OS way of implementing reuse and reclamation is relevant to DT? > I am considering introducing the vendor specific 'linux,dmb' property > that is dependent on the 'reusable' property to allow both the OS and > the device driver to identify the method used by the Linux OS to support > reuse and reclamation of the reserved-memory child node. Sure, but why? Why OS and Linux driver specific pieces should be in DT? > Such a property would remove any need for new compatible strings to the > device tree. Does that approach seem reasonable to you? No, because you did not explain original question. At all. Best regards, Krzysztof
