On Wed, 19 Mar 2014 19:51:21 +0100, Tomasz Figa wrote: > On 19.03.2014 19:37, Grant Grundler wrote: > > On Wed, Mar 19, 2014 at 10:30 AM, Tomasz Figa <t.figa@xxxxxxxxxxx> wrote: > > ... > >> As I said, AFAIK the trend is to get rid of ordering by initcalls and make > >> sure that drivers can handle missing dependencies properly, even for > >> "services" such as DMA, GPIO, clocks and so on, which after all are provided > >> by normal drivers like other. > > > > Ok - I'm not following the general kernel dev trends. initcall() > > levels are easy to understand and implement. So I would not be in a > > hurry to replace them. > > > > Well, initcall level is still a way to satisfy most of dependencies, > i.e. all client devices with higher initcall levels will probe > successfully. However the other case needs to be handled as well - in > this case the IOMMU binding code needs to defer probe of client driver > if respective IOMMU is not yet available. I now understand what is deferred probing you mentioned. However, I worry that many existing drivers are not ready for deferred probing. But still I wonder if System MMU driver need to be probed in the same initcall level. > >>> ps. I've written IOMMU support for four different IOMMUs on three > >>> operating systems (See drivers/parisc for two linux examples). But I > >>> still feel like I at best have 80% understanding of how this one is > >>> organized/works. Abstract descriptions and convoluted code have been > >>> handicapping me (and lack of time to dig further). > >> > >> > >> Well, this is one of my concerns with this driver. It isn't easy to read > >> (and so review, maintain, extend and debug found issues). > > > > My postscript comment was more to explain why I'm not confident in my > > opinion - not a reason to reject the patch series. I still consider > > the whole series as a step forward. But I'm not the expert here. > > I fully agree with you. Other than the issues mentioned in review, the > patches are definitely a step forward. I'd even say that all the patches > that have nothing to do with device tree could be merged in their > current form and the code refined later. It doesn't mean that patches > shouldn't be reviewed now and issues spotted reported, even if they > could be fixed later - this is for the IOMMU subsystem maintainer to decide. > > As for patches related to DT support, more care needs to be taken, as > bindings should be designed with stability in mind, so the refining > process should happen at review stage. > > > Right now, with ~30 patches posted by the exynos iommu (official?) > > maintainer, no one else who has a clue will attempt to fix or clean up > > those kinds of problems. i.e. it's useful to enable others to fix > > what are essentially unspecified "design pattern" issues. > > Agreed. Let me wait for the way of binding System MMU and its master developed by Marek. Regards, KyongHo -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
