On Mon, 2023-04-03 at 17:47 +0200, Paul Cercueil wrote: > Hi Jonathan, > > Here's the v3 of my patchset that introduces a new interface based on > DMABUF objects to complement the fileio API, and adds write() support to > the existing fileio API. > > It changed quite a lot since V2; the IIO subsystem is now just a DMABUF > importer, and all the complexity related to handling creation, deletion > and export of DMABUFs (including DMA mapping etc.) is gone. > > This new interface will be used by Libiio. The code is ready[1] and will > be merged to the main branch as soon as the kernel bits are accepted > upstream. > > Note that Libiio (and its server counterpart, iiod) use this new > interface in two different ways: > - by memory-mapping the DMABUFs to access the sample data directly, > which is much faster than using the existing fileio API as the sample > data does not need to be copied; > - by passing the DMABUFs around directly to the USB stack, in a > device-to-device zero-copy fashion, using a new DMABUF interface for > the USB (FunctionFS to be exact) stack, which is being upstreamed in > parallel of this patchset [2]. > > As for write() support, Nuno (Cc'd) said he will work on upstreaming the > DAC counterpart of adc/adi-axi-adc.c in the next few weeks, so there > will be a user for the buffer write() support. I hope you are okay with > this - otherwise, we can just wait until this work is done, and I still > benefit from sending this patchset early to get feedback. > Indeed, I already started a discussion [1] since what we have now for adc/adi-axi-adc.c has some major flaws (IMHO). So I'm hopping to get some feedback/discussion to get "righter" from the beginning. [1]: https://lore.kernel.org/linux-iio/dac3967805d7ddbd4653ead6d50e614844e0b70b.camel@xxxxxxxxx/T/#u - Nuno Sá
