On Fri, Jan 20, 2017 at 04:32:29PM +0100, Benjamin Gaignard wrote:
> The goal of this RFC is to understand if a common ioctl for specific memory
> regions allocations is needed/welcome.
>
> Obviously it will not replace allocation done in linux kernel frameworks like
> v4l2, drm/kms or others, but offer an alternative when you don't want/need to
> use them for buffer allocation.
> To keep a compatibility with what already exist allocated buffers are exported
> in userland as dmabuf file descriptor (like ION is doing).
>
> "Unix Device Memory Allocator" project [1] wants to create a userland library
> which may allow to select, depending of the devices constraint, the best
> back-end for allocation. With this RFC I would to propose to have common ioctl
> for a maximum of allocators to avoid to duplicated back-ends for this library.
>
> One of the issues that lead me to propose this RFC it is that since the beginning
> it is a problem to allocate contiguous memory (CMA) without using v4l2 or
> drm/kms so the first allocator available in this RFC use CMA memory.
>
> An other question is: do we have others memory regions that could be interested
> by this new framework ? I have in mind that some title memory regions could use
> it or replace ION heaps (system, carveout, etc...).
> Maybe it only solve CMA allocation issue, in this case there is no need to create
> a new framework but only a dedicated ioctl.
>
> Maybe the first thing to do is to change the name and the location of this
> module, suggestions are welcome.
>
> I have testing this code with the following program:
I'm still maintaining that we should just destage ION (with the todo items
fixed), since that is already an uabi to do this (afaiui at least), and
it's used on a few devices ... Please chat with Laura Abott.
-Daniel
>
> #include <errno.h>
> #include <fcntl.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <unistd.h>
> #include <sys/ioctl.h>
> #include <sys/mman.h>
> #include <sys/stat.h>
> #include <sys/types.h>
>
> #include "simple-allocator.h"
>
> #define LENGTH 1024*16
>
> void main (void)
> {
> struct simple_allocate_data data;
> int fd = open("/dev/cma0", O_RDWR, 0);
> int ret;
> void *mem;
>
> if (fd < 0) {
> printf("Can't open /dev/cma0\n");
> return;
> }
>
> memset(&data, 0, sizeof(data));
>
> data.length = LENGTH;
> data.flags = O_RDWR | O_CLOEXEC;
>
> ret = ioctl(fd, SA_IOC_ALLOC, &data);
> if (ret) {
> printf("Buffer allocation failed\n");
> goto end;
> }
>
> mem = mmap(0, LENGTH, PROT_READ | PROT_WRITE, MAP_SHARED, data.fd, 0);
> if (mem == MAP_FAILED) {
> printf("mmap failed\n");
> }
>
> memset(mem, 0xFF, LENGTH);
> munmap(mem, LENGTH);
>
> printf("test simple allocator CMA OK\n");
> end:
> close(fd);
> }
>
> [1] https://github.com/cubanismo/allocator
>
> Benjamin Gaignard (2):
> Create Simple Allocator module
> add CMA simple allocator module
>
> Documentation/simple-allocator.txt | 81 ++++++++++
> drivers/Kconfig | 2 +
> drivers/Makefile | 1 +
> drivers/simpleallocator/Kconfig | 17 +++
> drivers/simpleallocator/Makefile | 2 +
> drivers/simpleallocator/simple-allocator-cma.c | 187 ++++++++++++++++++++++++
> drivers/simpleallocator/simple-allocator-priv.h | 33 +++++
> drivers/simpleallocator/simple-allocator.c | 180 +++++++++++++++++++++++
> include/uapi/linux/simple-allocator.h | 35 +++++
> 9 files changed, 538 insertions(+)
> create mode 100644 Documentation/simple-allocator.txt
> create mode 100644 drivers/simpleallocator/Kconfig
> create mode 100644 drivers/simpleallocator/Makefile
> create mode 100644 drivers/simpleallocator/simple-allocator-cma.c
> create mode 100644 drivers/simpleallocator/simple-allocator-priv.h
> create mode 100644 drivers/simpleallocator/simple-allocator.c
> create mode 100644 include/uapi/linux/simple-allocator.h
>
> --
> 1.9.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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