**** BEGIN LOGGING AT Fri Jun 06 03:00:00 2014
Jun 06 04:31:52 <karki> panto : shared memory works. Now I'm have created sysfs entries for toggling IO pins + another sysfs entry for shared memory b/w kernel and PRU (kernel sends a value to the PRU via shared memory, PRU manipulates it as expected and returns )
Jun 06 04:31:59 <karki> panto : :)
Jun 06 09:49:48 <karki> panto : So now I have a single page of memory shared between the kernel and PRU. How do I export this to user space via mmap? I looked at a couple of sources, but in all the examples the "vm_area_struct" which we are getting via the param seems to have all the values populated beforehand. How does that work? how do I map to an existing page in kernel memory (which I've got  from dma_alloc_coherent) to userspace?
Jun 06 09:55:21 <Abhishek_> If you can get the physical address of the mem to user space then you could call mmap directly with that. IIRC UIO does it that way but I think there could be a better way
Jun 06 10:06:37 <karki> I didn't get you..... what do you mean "get the  physical address of the mem to user space" ?
Jun 06 10:08:36 <Abhishek_> Export a value via sysfs?
Jun 06 10:09:15 <karki> oh, idk about that
Jun 06 10:09:33 <karki> how could you call mmap with the physical addr again?
Jun 06 10:10:19 <karki> AFAIK the userspace is completely clueless about the physical addr that is getting mapped!
Jun 06 10:10:19 <panto> first things first
Jun 06 10:10:40 <panto> it might be bad to export the area you got from dma_alloc_coherent
Jun 06 10:11:04 <panto> you need the physical address of an area in memory that has no other mappings in ARM
Jun 06 10:11:38 <Abhishek_> ah
Jun 06 10:12:08 <Abhishek_> But then how does UIO do it?
Jun 06 10:12:12 <karki> okay, so do the mmap first
Jun 06 10:12:34 <karki> get the resulting physical addr that has been assigned
Jun 06 10:12:40 <karki> and give that to the PRU
Jun 06 10:13:55 * Abhishek_ is experiencing bad connectivity right now
Jun 06 10:13:58 <karki> physical address being (vm->vm_pgoff) >> PAGE_SHIFT
Jun 06 10:13:59 <panto> hmm, it just passes that to uio
Jun 06 10:14:05 <panto> I'm not sure this is correct
Jun 06 10:14:18 <panto> it might work, but it could be bad
Jun 06 10:14:31 <panto> anyway, use dma_coherent for now
Jun 06 10:14:39 <panto> I'll ask mdp when he shoes up
Jun 06 10:14:41 <panto> *shows
Jun 06 10:14:44 <panto> https://www.kernel.org/doc/Documentation/dma-buf-sharing.txt
Jun 06 10:14:52 <panto> but this is the modern interface to use
Jun 06 10:17:45 <Abhishek_> Going throught it
Jun 06 10:40:34 <panto> Abhishek_, karki, please send me via email links to your kernel trees
Jun 06 10:50:53 <karki> panto : I have mailed it to your gmail id.
Jun 06 10:53:34 <panto> ok
Jun 06 11:03:48 <Abhishek_> panto: I've sent it to your gmail id as well
Jun 06 11:08:25 <karki> what exactly is an anonymous file?
Jun 06 11:19:08 <panto> one that only exists in memory and not in the filesystem
Jun 06 11:20:33 <karki> like sysfs procfs etc?
Jun 06 11:20:40 <Abhishek_> panto: isn't it more suited for shared DMA between drivers than kernel->userspace?
Jun 06 11:21:09 <Abhishek_> karki: that's a filesystem
Jun 06 11:21:47 <Abhishek_> I think it more like an already opened file with a file number so that I can do whatever I want with the file without caring how it was opened
Jun 06 11:24:51 <karki> ah, yes. I read it as "a file that exists in memory, not on the disk"
Jun 06 11:24:54 <karki> :p
Jun 06 11:24:56 <karki> my bad
Jun 06 14:34:52 <karki> rseethamraju : hows it going ?
Jun 06 14:35:01 <rseethamraju> ok
Jun 06 14:35:10 <rseethamraju> nnot that great!
Jun 06 14:35:14 <rseethamraju> stupid exams
Jun 06 14:35:14 <Abhishek1> how many exams left?
Jun 06 14:35:16 <rseethamraju> 3
Jun 06 14:35:20 <rseethamraju> 2 over
Jun 06 14:41:16 <karki> which semester are you in?
Jun 06 14:42:38 <rseethamraju> 3-2
Jun 06 14:42:40 <rseethamraju> you?
Jun 06 14:43:02 <karki> done with 6th (including results)
Jun 06 14:43:05 <karki> phew
Jun 06 14:43:09 <karki> glad that is over
Jun 06 14:43:44 <rseethamraju> oh same here I mean getting done with 6th
Jun 06 14:43:51 <karki> :)
Jun 06 14:43:54 * Abhishek1 is done with his 4th sem results with a GPA of 9.41 so far
Jun 06 14:44:10 <rseethamraju> and my reaults will take a min of 2 months  :)
Jun 06 14:44:29 <rseethamraju> Abhishek1: wow! I have 65%
Jun 06 14:45:01 <karki> 9.7 ;)
Jun 06 14:45:13 <Abhishek1> cool ;)
Jun 06 14:45:20 <rseethamraju> seriuosly my exams are screwed anyway
Jun 06 14:45:23 <rseethamraju> JNTU
Jun 06 14:45:24 <rseethamraju> so
Jun 06 14:45:40 <rseethamraju> and Andhra you know with a 100 clgs in hyd and all
Jun 06 14:45:47 <rseethamraju> 9.9
Jun 06 14:46:32 <rseethamraju> but my branch highest in the uni is 78 so I’m hoping that’ll carry me through
Jun 06 14:46:41 <rseethamraju> karki: Wow!
Jun 06 14:47:04 <karki> scoring all depends on the university
Jun 06 14:47:15 <karki> individually CGPA mean nothing
Jun 06 14:47:39 <karki> so I stopped caring about CGPA long back. best thing I did
Jun 06 14:47:47 <rseethamraju> huh?
Jun 06 14:47:47 <Abhishek1> yep it's all relative anyways
Jun 06 14:48:11 <rseethamraju> It’ll still be quite a prb for me anyway
Jun 06 14:48:20 <rseethamraju> well whatever!
Jun 06 14:48:31 <rseethamraju> so hows GSoC going for you guys?
Jun 06 14:56:50 <Abhishek1> going well, but needs to build up more traction.
Jun 06 16:58:33 * karki 's BBB strikes again :/
**** ENDING LOGGING AT Sat Jun 07 02:59:59 2014