Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: Question: how to copy to user space from a tasklet | Date | Fri, 15 Oct 2010 10:59:40 +0200 |
| |
On Friday 15 October 2010 07:57:59 Stefan Richter wrote: > Tom Brown wrote: > > [Sorry to have to ask this here - I can't find any driver-specific > > newsgroup or mailing lists - are there any??] > > linux-newbie perhaps. > > > I have a driver which needs to copy device data direct to user space > > from a tasklet. > > One way would be to use mmap() to allocate the DMA buffer and insert it into > the user address space before DMA commences. An additional poll/read/write > based protocol or so can be used for buffer management during DMA.
Agreed, that would be best, it's a lot easier than the way Tom describes the driver to work today.
Just for completeness: doing DMA to random user address would require the process to register the area using some home grown interface, so that the driver can do get_user_pages/kmap on all of them and subsequently pass around an array of pages, while keeping track of ulimits and coherency with the existing kernel mappings. Don't do that.
Arnd
| |