Re: [RFC simple allocator v2 1/2] Create Simple Allocator module

[Laurent Pinchart]

Hi Daniel,

On Tuesday 14 Feb 2017 20:33:58 Daniel Vetter wrote:
> On Mon, Feb 13, 2017 at 3:45 PM, Benjamin Gaignard wrote:
> > This is the core of simple allocator module.
> > It aim to offert one common ioctl to allocate specific memory.
> > 
> > version 2:
> > - rebased on 4.10-rc7
> > 
> > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
> 
> Why not ION? It's a bit a broken record question, but if there is a
> clear answer it should be in the patch&docs ...

There's a bit of love & hate relationship between Linux developers and ION. 
The API has shortcomings, and attempts to fix the issues went nowhere. As 
Laura explained, starting from a blank slate (obviously keeping in mind the 
lessons learnt so far with ION and other similar APIs) and then adding a 
wrapper to expose ION on Android systems (at least as an interim measure) was 
thought to be a better option. I still believe it is, but we seem to lack 
traction. The problem has been around for so long that I feel everybody has 
lost hope.

I don't think this is unsolvable, but we need to regain motivation. In my 
opinion the first step would be to define the precise extent of the problem we 
want to solve.

> > ---
> > 
> >  Documentation/simple-allocator.txt              |  81 +++++++++++
> >  drivers/Kconfig                                 |   2 +
> >  drivers/Makefile                                |   1 +
> >  drivers/simpleallocator/Kconfig                 |  10 ++
> >  drivers/simpleallocator/Makefile                |   1 +
> >  drivers/simpleallocator/simple-allocator-priv.h |  33 +++++
> >  drivers/simpleallocator/simple-allocator.c      | 180 +++++++++++++++++++
> >  include/uapi/linux/simple-allocator.h           |  35 +++++
> >  8 files changed, 343 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-priv.h
> >  create mode 100644 drivers/simpleallocator/simple-allocator.c
> >  create mode 100644 include/uapi/linux/simple-allocator.h
> > 
> > diff --git a/Documentation/simple-allocator.txt
> > b/Documentation/simple-allocator.txt new file mode 100644
> > index 0000000..89ba883
> > --- /dev/null
> > +++ b/Documentation/simple-allocator.txt
> > @@ -0,0 +1,81 @@
> > +Simple Allocator Framework
> > +
> > +Simple Allocator offer a single ioctl SA_IOC_ALLOC to allocate buffers
> > +on dedicated memory regions and export them as a dmabuf file descriptor.
> > +Using dmabuf file descriptor allow to share this memory between processes
> > +and/or import it into other frameworks like v4l2 or drm/kms (prime).
> > +When userland wants to free the memory only a call to close() in needed
> > +so it could done even without knowing that buffer has been allocated by
> > +simple allocator ioctl.
> > +
> > +Each memory regions will be seen as a filein /dev/.
> > +For example CMA regions will exposed has /dev/cmaX.
> > +
> > +Implementing a simple allocator
> > +-------------------------------
> > +
> > +Simple Allocator provide helpers functions to register/unregister an
> > +allocator:
> > +- simple_allocator_register(struct sa_device *sadev)
> > +  Register simple_allocator_device using sa_device structure where name,
> > +  owner and allocate fields must be set.
> > +
> > +- simple_allocator_unregister(struct sa_device *sadev)
> > +  Unregister a simple allocator device.
> > +
> > +Using Simple Allocator /dev interface example
> > +---------------------------------------------
> > +
> > +This example of code allocate a buffer on the first CMA region
> > (/dev/cma0)
> > +before mmap and close it.
> > +
> > +#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);
> > +}
> > diff --git a/drivers/Kconfig b/drivers/Kconfig
> > index e1e2066..a6d8828 100644
> > --- a/drivers/Kconfig
> > +++ b/drivers/Kconfig
> > @@ -202,4 +202,6 @@ source "drivers/hwtracing/intel_th/Kconfig"
> > 
> >  source "drivers/fpga/Kconfig"
> > 
> > +source "drivers/simpleallocator/Kconfig"
> > +
> > 
> >  endmenu
> > 
> > diff --git a/drivers/Makefile b/drivers/Makefile
> > index 060026a..5081eb8 100644
> > --- a/drivers/Makefile
> > +++ b/drivers/Makefile
> > @@ -173,3 +173,4 @@ obj-$(CONFIG_STM)           += hwtracing/stm/
> > 
> >  obj-$(CONFIG_ANDROID)          += android/
> >  obj-$(CONFIG_NVMEM)            += nvmem/
> >  obj-$(CONFIG_FPGA)             += fpga/
> > 
> > +obj-$(CONFIG_SIMPLE_ALLOCATOR)         += simpleallocator/
> > diff --git a/drivers/simpleallocator/Kconfig
> > b/drivers/simpleallocator/Kconfig new file mode 100644
> > index 0000000..c6fc2e3
> > --- /dev/null
> > +++ b/drivers/simpleallocator/Kconfig
> > @@ -0,0 +1,10 @@
> > +menu "Simple Allocator"
> > +
> > +config SIMPLE_ALLOCATOR
> > +       tristate "Simple Alllocator Framework"
> > +       select DMA_SHARED_BUFFER
> > +       ---help---
> > +          The Simple Allocator Framework adds an API to allocate and
> > share
> > +          memory in userland.
> > +
> > +endmenu
> > diff --git a/drivers/simpleallocator/Makefile
> > b/drivers/simpleallocator/Makefile new file mode 100644
> > index 0000000..e27c6ad
> > --- /dev/null
> > +++ b/drivers/simpleallocator/Makefile
> > @@ -0,0 +1 @@
> > +obj-$(CONFIG_SIMPLE_ALLOCATOR) += simple-allocator.o
> > diff --git a/drivers/simpleallocator/simple-allocator-priv.h
> > b/drivers/simpleallocator/simple-allocator-priv.h new file mode 100644
> > index 0000000..33f5a33
> > --- /dev/null
> > +++ b/drivers/simpleallocator/simple-allocator-priv.h
> > @@ -0,0 +1,33 @@
> > +/*
> > + * Copyright (C) Linaro 2016
> > + *
> > + * Author: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
> > + *
> > + * License terms:  GNU General Public License (GPL)
> > + */
> > +
> > +#ifndef _SIMPLE_ALLOCATOR_PRIV_H_
> > +#define _SIMPLE_ALLOCATOR_PRIV_H_
> > +
> > +#include <linux/cdev.h>
> > +#include <linux/device.h>
> > +#include <linux/dma-buf.h>
> > +
> > +/**
> > + * struct sa_device - simple allocator device
> > + * @owner: module owner, must be set to THIS_MODULE
> > + * @name: name of the allocator
> > + * @allocate: callabck for memory allocation
> > + */
> > +struct sa_device {
> > +       struct device   dev;
> > +       struct cdev     chrdev;
> > +       struct module   *owner;
> > +       const char      *name;
> > +       struct dma_buf *(*allocate)(struct sa_device *, u64 length, u32
> > flags); +};
> > +
> > +int simple_allocator_register(struct sa_device *sadev);
> > +void simple_allocator_unregister(struct sa_device *sadev);
> > +
> > +#endif
> > diff --git a/drivers/simpleallocator/simple-allocator.c
> > b/drivers/simpleallocator/simple-allocator.c new file mode 100644
> > index 0000000..d89ccbf
> > --- /dev/null
> > +++ b/drivers/simpleallocator/simple-allocator.c
> > @@ -0,0 +1,180 @@
> > +/*
> > + * Copyright (C) Linaro 2016
> > + *
> > + * Author: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
> > + *
> > + * License terms:  GNU General Public License (GPL)
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/simple-allocator.h>
> > +#include <linux/uaccess.h>
> > +
> > +#include "simple-allocator-priv.h"
> > +
> > +#define SA_MAJOR       222
> > +#define SA_NUM_DEVICES 256
> > +#define SA_NAME                "simple_allocator"
> > +
> > +static int sa_minor;
> > +
> > +static struct class sa_class = {
> > +       .name = SA_NAME,
> > +};
> > +
> > +static long sa_ioctl(struct file *filp, unsigned int cmd, unsigned long
> > arg) +{
> > +       struct sa_device *sadev = filp->private_data;
> > +       int ret = -ENODEV;
> > +
> > +       switch (cmd) {
> > +       case SA_IOC_ALLOC:
> > +       {
> > +               struct simple_allocate_data data;
> > +               struct dma_buf *dmabuf;
> > +
> > +               if (copy_from_user(&data, (void __user *)arg,
> > _IOC_SIZE(cmd))) +                       return -EFAULT;
> > +
> > +               if (data.version != 0)
> > +                       return -EINVAL;
> > +
> > +               dmabuf = sadev->allocate(sadev, data.length, data.flags);
> > +               if (!dmabuf)
> > +                       return -EINVAL;
> > +
> > +               data.fd = dma_buf_fd(dmabuf, data.flags);
> > +               if (data.fd < 0) {
> > +                       dma_buf_put(dmabuf);
> > +                       return -EINVAL;
> > +               }
> > +
> > +               data.length = dmabuf->size;
> > +
> > +               if (copy_to_user((void __user *)arg, &data,
> > _IOC_SIZE(cmd))) { +                       dma_buf_put(dmabuf);
> > +                       return -EFAULT;
> > +               }
> > +
> > +               return 0;
> > +       }
> > +       }
> > +       return ret;
> > +}
> > +
> > +static int sa_open(struct inode *inode, struct file *filp)
> > +{
> > +       struct sa_device *sadev = container_of(inode->i_cdev,
> > +                                              struct sa_device, chrdev);
> > +
> > +       if (!sadev)
> > +               return -ENODEV;
> > +
> > +       get_device(&sadev->dev);
> > +       filp->private_data = sadev;
> > +       return 0;
> > +}
> > +
> > +static int sa_release(struct inode *inode, struct file *filp)
> > +{
> > +       struct sa_device *sadev = container_of(inode->i_cdev,
> > +                                              struct sa_device, chrdev);
> > +
> > +       if (!sadev)
> > +               return -ENODEV;
> > +
> > +       put_device(&sadev->dev);
> > +       return 0;
> > +}
> > +
> > +static const struct file_operations sa_fops = {
> > +       .owner = THIS_MODULE,
> > +       .open = sa_open,
> > +       .release = sa_release,
> > +       .unlocked_ioctl = sa_ioctl,
> > +};
> > +
> > +/**
> > + * simple_allocator_register - register a simple allocator
> > + * @sadev: simple allocator structure to be registered
> > + *
> > + * Return 0 if allocator has been regsitered, either a negative value.
> > + */
> > +int simple_allocator_register(struct sa_device *sadev)
> > +{
> > +       int ret;
> > +
> > +       if (!sadev->name || !sadev->allocate)
> > +               return -EINVAL;
> > +
> > +       cdev_init(&sadev->chrdev, &sa_fops);
> > +       sadev->chrdev.owner = sadev->owner;
> > +
> > +       ret = cdev_add(&sadev->chrdev, MKDEV(SA_MAJOR, sa_minor), 1);
> > +       if (ret < 0)
> > +               return ret;
> > +
> > +       sadev->dev.class = &sa_class;
> > +       sadev->dev.devt = MKDEV(SA_MAJOR, sa_minor);
> > +       dev_set_name(&sadev->dev, "%s%d", sadev->name, sa_minor);
> > +       ret = device_register(&sadev->dev);
> > +       if (ret < 0)
> > +               goto cleanup;
> > +
> > +       sa_minor++;
> > +       return 0;
> > +
> > +cleanup:
> > +       cdev_del(&sadev->chrdev);
> > +       return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(simple_allocator_register);
> > +
> > +/**
> > + * simple_allocator_unregister - unregister a simple allocator
> > + * @sadev: simple allocator device to be unregistered
> > + */
> > +void simple_allocator_unregister(struct sa_device *sadev)
> > +{
> > +       if (!sadev)
> > +               return;
> > +
> > +       cdev_del(&sadev->chrdev);
> > +       device_del(&sadev->dev);
> > +       put_device(&sadev->dev);
> > +}
> > +EXPORT_SYMBOL_GPL(simple_allocator_unregister);
> > +
> > +static int __init sa_init(void)
> > +{
> > +       dev_t dev = MKDEV(SA_MAJOR, 0);
> > +       int ret;
> > +
> > +       ret = register_chrdev_region(dev, SA_NUM_DEVICES, SA_NAME);
> > +       if (ret < 0)
> > +               return ret;
> > +
> > +       ret = class_register(&sa_class);
> > +       if (ret < 0) {
> > +               unregister_chrdev_region(dev, SA_NUM_DEVICES);
> > +               return -EIO;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static void __exit sa_exit(void)
> > +{
> > +       dev_t dev = MKDEV(SA_MAJOR, 0);
> > +
> > +       class_unregister(&sa_class);
> > +       unregister_chrdev_region(dev, SA_NUM_DEVICES);
> > +}
> > +
> > +subsys_initcall(sa_init);
> > +module_exit(sa_exit);
> > +
> > +MODULE_AUTHOR("Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>");
> > +MODULE_DESCRIPTION("Simple allocator");
> > +MODULE_LICENSE("GPL");
> > +MODULE_ALIAS_CHARDEV_MAJOR(SA_MAJOR);
> > diff --git a/include/uapi/linux/simple-allocator.h
> > b/include/uapi/linux/simple-allocator.h new file mode 100644
> > index 0000000..5520a85
> > --- /dev/null
> > +++ b/include/uapi/linux/simple-allocator.h
> > @@ -0,0 +1,35 @@
> > +/*
> > + * Copyright (C) Linaro 2016
> > + *
> > + * Author: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
> > + *
> > + * License terms:  GNU General Public License (GPL), version 2
> > + */
> > +
> > +#ifndef _SIMPLE_ALLOCATOR_H_
> > +#define _SIMPLE_ALLOCATOR_H_
> > +
> > +#include <linux/ioctl.h>
> > +#include <linux/types.h>
> > +
> > +/**
> > + * struct simple_allocate_data - allocation parameters
> > + * @version:   structure version (must be set to 0)
> > + * @length:    size of the requested buffer
> > + * @flags:     mode flags for the file like O_RDWR or O_CLOEXEC
> > + * @fd:                returned file descriptor
> > + */
> > +struct simple_allocate_data {
> > +       __u64 version;
> > +       __u64 length;
> > +       __u32 flags;
> > +       __u32 reserved1;
> > +       __s32 fd;
> > +       __u32 reserved2;
> > +};
> > +
> > +#define SA_IOC_MAGIC 'S'
> > +
> > +#define SA_IOC_ALLOC _IOWR(SA_IOC_MAGIC, 0, struct simple_allocate_data)
> > +
> > +#endif
> > --
> > 1.9.1

-- 
Regards,

Laurent Pinchart