Messages in this thread |  | | From | Arnd Bergmann <> | | Date | Fri, 1 Apr 2022 09:53:00 +0200 | | Subject | Re: [PATCH] habanalabs: fix build warning |
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On Fri, Apr 1, 2022 at 8:55 AM Oded Gabbay <ogabbay@kernel.org> wrote: > On Fri, Apr 1, 2022 at 9:40 AM Arnd Bergmann <arnd@arndb.de> wrote: > > On Fri, Apr 1, 2022 at 6:16 AM Max Filippov <jcmvbkbc@gmail.com> wrote: > > We use gen_pool in this function to manage our device memory > allocations (this is why it is called alloc_device_memory).
Ok, so it's none of the three I listed ;-)
> Basically, we initialize the genpool with the total size of the device memory, > and each bit represents a page according to a fixed page size, which > is dependent on asic type. > The addresses represent the physical address of the device memory, as > our device sees them. > As these addresses are not accessible from the host, it is appropriate > to hold them in u64, imo. > > For future asics which will support multiple page sizes, we need to > use the gen_pool_dma_alloc_align() variant, > because then we need the allocation to be aligned to the page size as > requested by the user per allocation. > > We ignore the DMA address because this is device memory, not host memory. > Therefore, our device's dma engine addresses the memory using the > virtual memory addresses we assign to it in our device's MMU. > > Having said that, I'm wondering whether gen_pool_first_fit_align() can > also work here, which might be less confusing.
Thank you for the explanation. I think the best way to make this less confusing and to avoid the type casts would be to define your own typedef for a device-internal address, and then wrap the allocator functions such as gen_pool_dma_alloc_align() in helper functions that do the type conversion safely.
Arnd
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