Date:   Wed, 6 Mar 2019 17:12:24 +0100
From:   Benjamin Gaignard <benjamin.gaignard@...aro.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        "Andrew F. Davis" <afd@...com>, Laura Abbott <labbott@...hat.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Brian Starkey <Brian.Starkey@....com>,
        Chenbo Feng <fengc@...gle.com>,
        Alistair Strachan <astrachan@...gle.com>,
        ML dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [RFC][PATCH 1/5 v2] dma-buf: Add dma-buf heaps framework

Le mar. 5 mars 2019 à 21:54, John Stultz <john.stultz@...aro.org> a écrit :
>
> From: "Andrew F. Davis" <afd@...com>
>
> This framework allows a unified userspace interface for dma-buf
> exporters, allowing userland to allocate specific types of
> memory for use in dma-buf sharing.
>
> Each heap is given its own device node, which a user can
> allocate a dma-buf fd from using the DMA_HEAP_IOC_ALLOC.
>
> This code is an evoluiton of the Android ION implementation,
> and a big thanks is due to its authors/maintainers over time
> for their effort:
>   Rebecca Schultz Zavin, Colin Cross, Benjamin Gaignard,
>   Laura Abbott, and many other contributors!
>
> Cc: Laura Abbott <labbott@...hat.com>
> Cc: Benjamin Gaignard <benjamin.gaignard@...aro.org>
> Cc: Greg KH <gregkh@...uxfoundation.org>
> Cc: Sumit Semwal <sumit.semwal@...aro.org>
> Cc: Liam Mark <lmark@...eaurora.org>
> Cc: Brian Starkey <Brian.Starkey@....com>
> Cc: Andrew F. Davis <afd@...com>
> Cc: Chenbo Feng <fengc@...gle.com>
> Cc: Alistair Strachan <astrachan@...gle.com>
> Cc: dri-devel@...ts.freedesktop.org
> Signed-off-by: Andrew F. Davis <afd@...com>
> [jstultz: reworded commit message, and lots of cleanups]
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
> v2:
> * Folded down fixes I had previously shared in implementing
>   heaps
> * Make flags a u64 (Suggested by Laura)
> * Add PAGE_ALIGN() fix to the core alloc funciton
> * IOCTL fixups suggested by Brian
> * Added fixes suggested by Benjamin
> * Removed core stats mgmt, as that should be implemented by
>   per-heap code
> * Changed alloc to return a dma-buf fd, rather then a buffer
>   (as it simplifies error handling)
> ---
>  MAINTAINERS                   |  16 ++++
>  drivers/dma-buf/Kconfig       |   8 ++
>  drivers/dma-buf/Makefile      |   1 +
>  drivers/dma-buf/dma-heap.c    | 191 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/dma-heap.h      |  65 ++++++++++++++
>  include/uapi/linux/dma-heap.h |  52 ++++++++++++
>  6 files changed, 333 insertions(+)
>  create mode 100644 drivers/dma-buf/dma-heap.c
>  create mode 100644 include/linux/dma-heap.h
>  create mode 100644 include/uapi/linux/dma-heap.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index ac2e518..a661e19 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -4621,6 +4621,22 @@ F:       include/linux/*fence.h
>  F:     Documentation/driver-api/dma-buf.rst
>  T:     git git://anongit.freedesktop.org/drm/drm-misc
>
> +DMA-BUF HEAPS FRAMEWORK
> +M:     Laura Abbott <labbott@...hat.com>
> +R:     Liam Mark <lmark@...eaurora.org>
> +R:     Brian Starkey <Brian.Starkey@....com>
> +R:     "Andrew F. Davis" <afd@...com>
> +R:     John Stultz <john.stultz@...aro.org>
> +S:     Maintained
> +L:     linux-media@...r.kernel.org
> +L:     dri-devel@...ts.freedesktop.org
> +L:     linaro-mm-sig@...ts.linaro.org (moderated for non-subscribers)
> +F:     include/uapi/linux/dma-heap.h
> +F:     include/linux/dma-heap.h
> +F:     drivers/dma-buf/dma-heap.c
> +F:     drivers/dma-buf/heaps/*
> +T:     git git://anongit.freedesktop.org/drm/drm-misc
> +
>  DMA GENERIC OFFLOAD ENGINE SUBSYSTEM
>  M:     Vinod Koul <vkoul@...nel.org>
>  L:     dmaengine@...r.kernel.org
> diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
> index 2e5a0fa..09c61db 100644
> --- a/drivers/dma-buf/Kconfig
> +++ b/drivers/dma-buf/Kconfig
> @@ -39,4 +39,12 @@ config UDMABUF
>           A driver to let userspace turn memfd regions into dma-bufs.
>           Qemu can use this to create host dmabufs for guest framebuffers.
>
> +menuconfig DMABUF_HEAPS
> +       bool "DMA-BUF Userland Memory Heaps"
> +       select DMA_SHARED_BUFFER
> +       help
> +         Choose this option to enable the DMA-BUF userland memory heaps,
> +         this allows userspace to allocate dma-bufs that can be shared between
> +         drivers.
> +
>  endmenu
> diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile
> index 0913a6c..b0332f1 100644
> --- a/drivers/dma-buf/Makefile
> +++ b/drivers/dma-buf/Makefile
> @@ -1,4 +1,5 @@
>  obj-y := dma-buf.o dma-fence.o dma-fence-array.o reservation.o seqno-fence.o
> +obj-$(CONFIG_DMABUF_HEAPS)     += dma-heap.o
>  obj-$(CONFIG_SYNC_FILE)                += sync_file.o
>  obj-$(CONFIG_SW_SYNC)          += sw_sync.o sync_debug.o
>  obj-$(CONFIG_UDMABUF)          += udmabuf.o
> diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
> new file mode 100644
> index 0000000..14b3975
> --- /dev/null
> +++ b/drivers/dma-buf/dma-heap.c
> @@ -0,0 +1,191 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Framework for userspace DMA-BUF allocations
> + *
> + * Copyright (C) 2011 Google, Inc.
> + * Copyright (C) 2019 Linaro Ltd.
> + */
> +
> +#include <linux/cdev.h>
> +#include <linux/debugfs.h>
> +#include <linux/device.h>
> +#include <linux/dma-buf.h>
> +#include <linux/err.h>
> +#include <linux/idr.h>
> +#include <linux/list.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +
> +#include <linux/dma-heap.h>
> +#include <uapi/linux/dma-heap.h>
> +
> +#define DEVNAME "dma_heap"
> +
> +#define NUM_HEAP_MINORS 128
> +static DEFINE_IDR(dma_heap_idr);
> +static DEFINE_MUTEX(minor_lock); /* Protect idr accesses */
> +
> +dev_t dma_heap_devt;
> +struct class *dma_heap_class;
> +struct list_head dma_heap_list;
> +struct dentry *dma_heap_debug_root;
> +
> +static int dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
> +                                unsigned int flags)
> +{
> +       len = PAGE_ALIGN(len);
> +       if (!len)
> +               return -EINVAL;
> +
> +       return heap->ops->allocate(heap, len, flags);
> +}
> +
> +static int dma_heap_open(struct inode *inode, struct file *filp)
> +{
> +       struct dma_heap *heap;
> +
> +       mutex_lock(&minor_lock);
> +       heap = idr_find(&dma_heap_idr, iminor(inode));
> +       mutex_unlock(&minor_lock);
> +       if (!heap) {
> +               pr_err("dma_heap: minor %d unknown.\n", iminor(inode));
> +               return -ENODEV;
> +       }
> +
> +       /* instance data as context */
> +       filp->private_data = heap;
> +       nonseekable_open(inode, filp);
> +
> +       return 0;
> +}
> +
> +static int dma_heap_release(struct inode *inode, struct file *filp)
> +{
> +       filp->private_data = NULL;
> +
> +       return 0;
> +}
> +
> +static long dma_heap_ioctl(struct file *filp, unsigned int cmd,
> +                          unsigned long arg)
> +{
> +       switch (cmd) {
> +       case DMA_HEAP_IOC_ALLOC:
> +       {
> +               struct dma_heap_allocation_data heap_allocation;
> +               struct dma_heap *heap = filp->private_data;
> +               int fd;
> +
> +               if (copy_from_user(&heap_allocation, (void __user *)arg,
> +                                  sizeof(heap_allocation)))
> +                       return -EFAULT;
> +
> +               if (heap_allocation.fd ||
> +                   heap_allocation.reserved0 ||
> +                   heap_allocation.reserved1 ||
> +                   heap_allocation.reserved2) {
> +                       pr_warn_once("dma_heap: ioctl data not valid\n");
> +                       return -EINVAL;
> +               }
> +               if (heap_allocation.flags & ~DMA_HEAP_VALID_FLAGS) {
> +                       pr_warn_once("dma_heap: flags has invalid or unsupported flags set\n");
> +                       return -EINVAL;
> +               }
> +
> +               fd = dma_heap_buffer_alloc(heap, heap_allocation.len,
> +                                          heap_allocation.flags);
> +               if (fd < 0)
> +                       return fd;
> +
> +               heap_allocation.fd = fd;
> +
> +               if (copy_to_user((void __user *)arg, &heap_allocation,
> +                                sizeof(heap_allocation)))
> +                       return -EFAULT;
> +
> +               break;
> +       }
> +       default:
> +               return -ENOTTY;
> +       }
> +
> +       return 0;
> +}
> +
> +static const struct file_operations dma_heap_fops = {
> +       .owner          = THIS_MODULE,
> +       .open           = dma_heap_open,
> +       .release        = dma_heap_release,
> +       .unlocked_ioctl = dma_heap_ioctl,
> +#ifdef CONFIG_COMPAT
> +       .compat_ioctl   = dma_heap_ioctl,
> +#endif
> +};
> +
> +int dma_heap_add(struct dma_heap *heap)
> +{
> +       struct device *dev_ret;
> +       int ret;
> +
> +       if (!heap->name || !strcmp(heap->name, "")) {
> +               pr_err("dma_heap: Cannot add heap without a name\n");
> +               return -EINVAL;
> +       }
> +
> +       if (!heap->ops || !heap->ops->allocate) {
> +               pr_err("dma_heap: Cannot add heap with invalid ops struct\n");
> +               return -EINVAL;
> +       }
> +
> +       /* Find unused minor number */
> +       mutex_lock(&minor_lock);
> +       ret = idr_alloc(&dma_heap_idr, heap, 0, NUM_HEAP_MINORS, GFP_KERNEL);
> +       mutex_unlock(&minor_lock);
> +       if (ret < 0) {
> +               pr_err("dma_heap: Unable to get minor number for heap\n");
> +               return ret;
> +       }
> +       heap->minor = ret;
> +
> +       /* Create device */
> +       heap->heap_devt = MKDEV(MAJOR(dma_heap_devt), heap->minor);
> +       dev_ret = device_create(dma_heap_class,
> +                               NULL,
> +                               heap->heap_devt,
> +                               NULL,
> +                               heap->name);
> +       if (IS_ERR(dev_ret)) {
> +               pr_err("dma_heap: Unable to create char device\n");
> +               return PTR_ERR(dev_ret);
> +       }
> +
> +       /* Add device */
> +       cdev_init(&heap->heap_cdev, &dma_heap_fops);
> +       ret = cdev_add(&heap->heap_cdev, dma_heap_devt, NUM_HEAP_MINORS);
> +       if (ret < 0) {
> +               device_destroy(dma_heap_class, heap->heap_devt);
> +               pr_err("dma_heap: Unable to add char device\n");
> +               return ret;
> +       }
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL(dma_heap_add);
> +
> +static int dma_heap_init(void)
> +{
> +       int ret;
> +
> +       ret = alloc_chrdev_region(&dma_heap_devt, 0, NUM_HEAP_MINORS, DEVNAME);
> +       if (ret)
> +               return ret;
> +
> +       dma_heap_class = class_create(THIS_MODULE, DEVNAME);
> +       if (IS_ERR(dma_heap_class)) {
> +               unregister_chrdev_region(dma_heap_devt, NUM_HEAP_MINORS);
> +               return PTR_ERR(dma_heap_class);
> +       }
> +
> +       return 0;
> +}
> +subsys_initcall(dma_heap_init);
> diff --git a/include/linux/dma-heap.h b/include/linux/dma-heap.h
> new file mode 100644
> index 0000000..ed86a8e
> --- /dev/null
> +++ b/include/linux/dma-heap.h
> @@ -0,0 +1,65 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * DMABUF Heaps Allocation Infrastructure
> + *
> + * Copyright (C) 2011 Google, Inc.
> + * Copyright (C) 2019 Linaro Ltd.
> + */
> +
> +#ifndef _DMA_HEAPS_H
> +#define _DMA_HEAPS_H
> +
> +#include <linux/cdev.h>
> +#include <linux/types.h>
> +
> +/**
> + * struct dma_heap_buffer - metadata for a particular buffer
> + * @heap:              back pointer to the heap the buffer came from
> + * @dmabuf:            backing dma-buf for this buffer
> + * @size:              size of the buffer
> + * @flags:             buffer specific flags
> + */
> +struct dma_heap_buffer {
> +       struct dma_heap *heap;
> +       struct dma_buf *dmabuf;
> +       size_t size;
> +       unsigned long flags;
> +};
> +
> +/**
> + * struct dma_heap - represents a dmabuf heap in the system
> + * @name:              used for debugging/device-node name
> + * @ops:               ops struct for this heap
> + * @minor              minor number of this heap device
> + * @heap_devt          heap device node
> + * @heap_cdev          heap char device
> + *
> + * Represents a heap of memory from which buffers can be made.
> + */
> +struct dma_heap {
> +       const char *name;
> +       struct dma_heap_ops *ops;
> +       unsigned int minor;
> +       dev_t heap_devt;
> +       struct cdev heap_cdev;
> +};
> +
> +/**
> + * struct dma_heap_ops - ops to operate on a given heap
> + * @allocate:          allocate dmabuf and return fd
> + *
> + * allocate returns dmabuf fd  on success, -errno on error.
> + */
> +struct dma_heap_ops {
> +       int (*allocate)(struct dma_heap *heap,
> +                       unsigned long len,
> +                       unsigned long flags);
> +};
> +
> +/**
> + * dma_heap_add - adds a heap to dmabuf heaps
> + * @heap:              the heap to add
> + */
> +int dma_heap_add(struct dma_heap *heap);
> +
> +#endif /* _DMA_HEAPS_H */
> diff --git a/include/uapi/linux/dma-heap.h b/include/uapi/linux/dma-heap.h
> new file mode 100644
> index 0000000..75c5d3f
> --- /dev/null
> +++ b/include/uapi/linux/dma-heap.h
> @@ -0,0 +1,52 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * DMABUF Heaps Userspace API
> + *
> + * Copyright (C) 2011 Google, Inc.
> + * Copyright (C) 2019 Linaro Ltd.
> + */
> +#ifndef _UAPI_LINUX_DMABUF_POOL_H
> +#define _UAPI_LINUX_DMABUF_POOL_H
> +
> +#include <linux/ioctl.h>
> +#include <linux/types.h>
> +
> +/**
> + * DOC: DMABUF Heaps Userspace API
> + *
> + */
> +
> +/* Currently no flags */
> +#define DMA_HEAP_VALID_FLAGS (0)

I think here you need to allow flags like O_RDWR or O_CLOEXEC else
mmap will fail.

Benjamin

> +
> +/**
> + * struct dma_heap_allocation_data - metadata passed from userspace for
> + *                                      allocations
> + * @len:               size of the allocation
> + * @flags:             flags passed to pool
> + * @fd:                        will be populated with a fd which provdes the
> + *                     handle to the allocated dma-buf
> + *
> + * Provided by userspace as an argument to the ioctl
> + */
> +struct dma_heap_allocation_data {
> +       __u64 len;
> +       __u64 flags;
> +       __u32 fd;
> +       __u32 reserved0;
> +       __u32 reserved1;
> +       __u32 reserved2;
> +};
> +
> +#define DMA_HEAP_IOC_MAGIC             'H'
> +
> +/**
> + * DOC: DMA_HEAP_IOC_ALLOC - allocate memory from pool
> + *
> + * Takes an dma_heap_allocation_data struct and returns it with the fd field
> + * populated with the dmabuf handle of the allocation.
> + */
> +#define DMA_HEAP_IOC_ALLOC     _IOWR(DMA_HEAP_IOC_MAGIC, 0, \
> +                                     struct dma_heap_allocation_data)
> +
> +#endif /* _UAPI_LINUX_DMABUF_POOL_H */
> --
> 2.7.4
>


-- 
Benjamin Gaignard

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