On Thu, 13 Feb 2014 13:48:40 -0600, Josh Cartwright <joshc@xxxxxxxxxxxxxx> wrote: > On Tue, Feb 11, 2014 at 09:27:36PM +0100, Tomasz Figa wrote: > > On 11.02.2014 21:19, Josh Cartwright wrote: > > >On Tue, Feb 11, 2014 at 09:04:21PM +0100, Tomasz Figa wrote: > > > >On 11.02.2014 21:02, Benjamin Herrenschmidt wrote: > > > > >On Tue, 2014-02-11 at 19:01 +0000, Grant Likely wrote: > > > > > > > except that the former IMHO better suits the definition of memory > > > > > > > region, which I see as a single contiguous range of memory and can be > > > > > > > simplified to have a single reg entry per region. > > > > > > > > > > > > My point is rather if multiple reg tuples are found in a reserved memory > > > > > > node, the kernel must respect them and reserve the memory. I'm not > > > > > > arguing about whether or not that makes for a good binding. > > > > > > > > > > agreed. > > > > > > > > My point is why, if the binding defines that just a single tuple should be > > > > provided. > > > > > > FWIW, the usecase I had mentioned in reply to Grant in the patch 5/5 > > > thread [1] could make use of this. The shared memory region is split > > > into a main chunk and several "auxiliary" chunk, but collectively these > > > regions all share the same heap state. > > > > > > Josh > > > > > > 1: http://lkml.kernel.org/r/20140205192502.GO20228@xxxxxxxxxxxxxxxxxx > > > > The use case seems fine, but I believe it could be properly represented in > > device tree using multiple single-reg regions as well, unless the consumer > > can request a block of memory that crosses boundary of two sub-regions > > specified by reg entries of single region. > > I could probably make a only-one-reg-entry policy work for me, but it > makes things a bit more awkward. I'd lose the ability to describe > "this set of regions need to be logically handled together" directly in > the reserved memory node, and would need to push it up a layer. > > reserved-memory { > smem: smem { > reg = <...>; > }; > aux1: auxiliary1 { > reg = <...>; > }; > aux2: auxiliary2 { > reg = <...>; > }; > ... > }; If the regions are used for different purposes, it makes sense I think to have a separate node for each. Multiple tuples would make more sense for something like valid DMA regions for a broken device that can only DMA into a few windows; you could have one tuple per window within a single node. It would be possible to collect multiple associated nodes under one parent node which in turn has reserved-memory for its parent: reserved-memory { ranges; reserved-group { ranges; smem: smem { reg = <...>; }; aux1: auxiliary1 { reg = <...>; }; aux2: auxiliary2 { reg = <...>; }; }; ... }; g. -- 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
