[v12,1/5] dma-buf: Add dma-buf heaps framework

Submitted by John Stultz on Oct. 18, 2019, 5:23 a.m.

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Message ID 20191018052323.21659-2-john.stultz@linaro.org
State New
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Series "DMA-BUF Heaps (destaging ION)" ( rev: 12 ) in DRI devel

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Commit Message

John Stultz Oct. 18, 2019, 5:23 a.m.
From: "Andrew F. Davis" <afd@ti.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@redhat.com>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Liam Mark <lmark@codeaurora.org>
Cc: Pratik Patel <pratikp@codeaurora.org>
Cc: Brian Starkey <Brian.Starkey@arm.com>
Cc: Vincent Donnefort <Vincent.Donnefort@arm.com>
Cc: Sudipto Paul <Sudipto.Paul@arm.com>
Cc: Andrew F. Davis <afd@ti.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Chenbo Feng <fengc@google.com>
Cc: Alistair Strachan <astrachan@google.com>
Cc: Hridya Valsaraju <hridya@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Reviewed-by: Brian Starkey <brian.starkey@arm.com>
Acked-by: Laura Abbott <labbott@redhat.com>
Tested-by: Ayan Kumar Halder <ayan.halder@arm.com>
Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: John Stultz <john.stultz@linaro.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 than a buffer
  (as it simplifies error handling)
v3:
* Removed scare-quotes in MAINTAINERS email address
* Get rid of .release function as it didn't do anything (from
  Christoph)
* Renamed filp to file (suggested by Christoph)
* Split out ioctl handling to separate function (suggested by
  Christoph)
* Add comment documenting PAGE_ALIGN usage (suggested by Brian)
* Switch from idr to Xarray (suggested by Brian)
* Fixup cdev creation (suggested by Brian)
* Avoid EXPORT_SYMBOL until we finalize modules (suggested by
  Brian)
* Make struct dma_heap internal only (folded in from Andrew)
* Small cleanups suggested by GregKH
* Provide class->devnode callback to get consistent /dev/
  subdirectory naming (Suggested by Bjorn)
v4:
* Folded down dma-heap.h change that was in a following patch
* Added fd_flags entry to allocation structure and pass it
  through to heap code for use on dma-buf fd creation (suggested
  by Benjamin)
v5:
* Minor cleanups
v6:
* Improved error path handling, minor whitespace fixes, both
  suggested by Brian
v7:
* Longer Kconfig description to quiet checkpatch warnings
* Re-add compat_ioctl bits (Hridya noticed 32bit userland wasn't
  working)
v8:
* Make struct dma_heap_ops consts (Suggested by Christoph)
* Checkpatch whitespace fixups
v9:
* Minor cleanups suggested by Brian Starkey
* Rename dma_heap_get_data->dma_heap_get_drvdata suggested
  by Hilf Danton
v11:
* Kconfig text improvements suggested by Randy Dunlap
v12:
* Add logic to prevent duplicately named heaps being added
* Add symbol exports for heaps as modules
---
 MAINTAINERS                   |  18 +++
 drivers/dma-buf/Kconfig       |   9 ++
 drivers/dma-buf/Makefile      |   1 +
 drivers/dma-buf/dma-heap.c    | 271 ++++++++++++++++++++++++++++++++++
 include/linux/dma-heap.h      |  59 ++++++++
 include/uapi/linux/dma-heap.h |  55 +++++++
 6 files changed, 413 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

Patch hide | download patch | download mbox

diff --git a/MAINTAINERS b/MAINTAINERS
index a69e6db80c79..591c4c484558 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4939,6 +4939,24 @@  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:	Sumit Semwal <sumit.semwal@linaro.org>
+R:	Andrew F. Davis <afd@ti.com>
+R:	Benjamin Gaignard <benjamin.gaignard@linaro.org>
+R:	Liam Mark <lmark@codeaurora.org>
+R:	Laura Abbott <labbott@redhat.com>
+R:	Brian Starkey <Brian.Starkey@arm.com>
+R:	John Stultz <john.stultz@linaro.org>
+S:	Maintained
+L:	linux-media@vger.kernel.org
+L:	dri-devel@lists.freedesktop.org
+L:	linaro-mm-sig@lists.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@kernel.org>
 L:	dmaengine@vger.kernel.org
diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
index a23b6752d11a..bffa58fc3e6e 100644
--- a/drivers/dma-buf/Kconfig
+++ b/drivers/dma-buf/Kconfig
@@ -44,4 +44,13 @@  config DMABUF_SELFTESTS
 	default n
 	depends on DMA_SHARED_BUFFER
 
+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 options creates per heap chardevs in /dev/dma_heap/ which
+	  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 03479da06422..caee5eb3d351 100644
--- a/drivers/dma-buf/Makefile
+++ b/drivers/dma-buf/Makefile
@@ -1,6 +1,7 @@ 
 # SPDX-License-Identifier: GPL-2.0-only
 obj-y := dma-buf.o dma-fence.o dma-fence-array.o dma-fence-chain.o \
 	 dma-resv.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 000000000000..15b7988a9b68
--- /dev/null
+++ b/drivers/dma-buf/dma-heap.c
@@ -0,0 +1,271 @@ 
+// 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/xarray.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/syscalls.h>
+#include <linux/dma-heap.h>
+#include <uapi/linux/dma-heap.h>
+
+#define DEVNAME "dma_heap"
+
+#define NUM_HEAP_MINORS 128
+
+/**
+ * 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;
+	const struct dma_heap_ops *ops;
+	void *priv;
+	unsigned int minor;
+	dev_t heap_devt;
+	struct list_head list;
+	struct cdev heap_cdev;
+};
+
+static LIST_HEAD(heap_list);
+static DEFINE_MUTEX(heap_list_lock);
+static dev_t dma_heap_devt;
+static struct class *dma_heap_class;
+static DEFINE_XARRAY_ALLOC(dma_heap_minors);
+
+static int dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
+				 unsigned int fd_flags,
+				 unsigned int heap_flags)
+{
+	/*
+	 * Allocations from all heaps have to begin
+	 * and end on page boundaries.
+	 */
+	len = PAGE_ALIGN(len);
+	if (!len)
+		return -EINVAL;
+
+	return heap->ops->allocate(heap, len, fd_flags, heap_flags);
+}
+
+static int dma_heap_open(struct inode *inode, struct file *file)
+{
+	struct dma_heap *heap;
+
+	heap = xa_load(&dma_heap_minors, iminor(inode));
+	if (!heap) {
+		pr_err("dma_heap: minor %d unknown.\n", iminor(inode));
+		return -ENODEV;
+	}
+
+	/* instance data as context */
+	file->private_data = heap;
+	nonseekable_open(inode, file);
+
+	return 0;
+}
+
+static long dma_heap_ioctl_allocate(struct file *file, unsigned long arg)
+{
+	struct dma_heap_allocation_data heap_allocation;
+	struct dma_heap *heap = file->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) {
+		pr_warn_once("dma_heap: ioctl data not valid\n");
+		return -EINVAL;
+	}
+
+	if (heap_allocation.fd_flags & ~DMA_HEAP_VALID_FD_FLAGS) {
+		pr_warn_once("dma_heap: fd_flags has invalid or unsupported flags set\n");
+		return -EINVAL;
+	}
+
+	if (heap_allocation.heap_flags & ~DMA_HEAP_VALID_HEAP_FLAGS) {
+		pr_warn_once("dma_heap: heap flags has invalid or unsupported flags set\n");
+		return -EINVAL;
+	}
+
+	fd = dma_heap_buffer_alloc(heap, heap_allocation.len,
+				   heap_allocation.fd_flags,
+				   heap_allocation.heap_flags);
+	if (fd < 0)
+		return fd;
+
+	heap_allocation.fd = fd;
+
+	if (copy_to_user((void __user *)arg, &heap_allocation,
+			 sizeof(heap_allocation))) {
+		ksys_close(fd);
+		return -EFAULT;
+	}
+
+	return 0;
+}
+
+static long dma_heap_ioctl(struct file *file, unsigned int cmd,
+			   unsigned long arg)
+{
+	int ret = 0;
+
+	switch (cmd) {
+	case DMA_HEAP_IOC_ALLOC:
+		ret = dma_heap_ioctl_allocate(file, arg);
+		break;
+	default:
+		return -ENOTTY;
+	}
+
+	return ret;
+}
+
+static const struct file_operations dma_heap_fops = {
+	.owner          = THIS_MODULE,
+	.open		= dma_heap_open,
+	.unlocked_ioctl = dma_heap_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= dma_heap_ioctl,
+#endif
+};
+
+/**
+ * dma_heap_get_drvdata() - get per-subdriver data for the heap
+ * @heap: DMA-Heap to retrieve private data for
+ *
+ * Returns:
+ * The per-subdriver data for the heap.
+ */
+void *dma_heap_get_drvdata(struct dma_heap *heap)
+{
+	return heap->priv;
+}
+EXPORT_SYMBOL_GPL(dma_heap_get_drvdata);
+
+struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
+{
+	struct dma_heap *heap, *h, *err_ret;
+	struct device *dev_ret;
+	int ret;
+
+	if (!exp_info->name || !strcmp(exp_info->name, "")) {
+		pr_err("dma_heap: Cannot add heap without a name\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (!exp_info->ops || !exp_info->ops->allocate) {
+		pr_err("dma_heap: Cannot add heap with invalid ops struct\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	/* check the name is unique */
+	mutex_lock(&heap_list_lock);
+	list_for_each_entry(h, &heap_list, list) {
+		if (!strcmp(h->name, exp_info->name)) {
+			mutex_unlock(&heap_list_lock);
+			pr_err("dma_heap: Already registered heap named %s\n",
+				exp_info->name);
+			return ERR_PTR(-EINVAL);
+		}
+	}
+	mutex_unlock(&heap_list_lock);
+
+	heap = kzalloc(sizeof(*heap), GFP_KERNEL);
+	if (!heap)
+		return ERR_PTR(-ENOMEM);
+
+	heap->name = exp_info->name;
+	heap->ops = exp_info->ops;
+	heap->priv = exp_info->priv;
+
+	/* Find unused minor number */
+	ret = xa_alloc(&dma_heap_minors, &heap->minor, heap,
+		       XA_LIMIT(0, NUM_HEAP_MINORS - 1), GFP_KERNEL);
+	if (ret < 0) {
+		pr_err("dma_heap: Unable to get minor number for heap\n");
+		err_ret = ERR_PTR(ret);
+		goto err0;
+	}
+
+	/* Create device */
+	heap->heap_devt = MKDEV(MAJOR(dma_heap_devt), heap->minor);
+
+	cdev_init(&heap->heap_cdev, &dma_heap_fops);
+	ret = cdev_add(&heap->heap_cdev, heap->heap_devt, 1);
+	if (ret < 0) {
+		pr_err("dma_heap: Unable to add char device\n");
+		err_ret = ERR_PTR(ret);
+		goto err1;
+	}
+
+	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 device\n");
+		err_ret = ERR_CAST(dev_ret);
+		goto err2;
+	}
+	/* Add heap to the list */
+	mutex_lock(&heap_list_lock);
+	list_add(&heap->list, &heap_list);
+	mutex_unlock(&heap_list_lock);
+
+	return heap;
+
+err2:
+	cdev_del(&heap->heap_cdev);
+err1:
+	xa_erase(&dma_heap_minors, heap->minor);
+err0:
+	kfree(heap);
+	return err_ret;
+}
+EXPORT_SYMBOL_GPL(dma_heap_add);
+
+static char *dma_heap_devnode(struct device *dev, umode_t *mode)
+{
+	return kasprintf(GFP_KERNEL, "dma_heap/%s", dev_name(dev));
+}
+
+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);
+	}
+	dma_heap_class->devnode = dma_heap_devnode;
+
+	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 000000000000..454e354d1ffb
--- /dev/null
+++ b/include/linux/dma-heap.h
@@ -0,0 +1,59 @@ 
+/* 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;
+
+/**
+ * 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 fd_flags,
+			unsigned long heap_flags);
+};
+
+/**
+ * struct dma_heap_export_info - information needed to export a new dmabuf heap
+ * @name:	used for debugging/device-node name
+ * @ops:	ops struct for this heap
+ * @priv:	heap exporter private data
+ *
+ * Information needed to export a new dmabuf heap.
+ */
+struct dma_heap_export_info {
+	const char *name;
+	const struct dma_heap_ops *ops;
+	void *priv;
+};
+
+/**
+ * dma_heap_get_drvdata() - get per-heap driver data
+ * @heap: DMA-Heap to retrieve private data for
+ *
+ * Returns:
+ * The per-heap data for the heap.
+ */
+void *dma_heap_get_drvdata(struct dma_heap *heap);
+
+/**
+ * dma_heap_add - adds a heap to dmabuf heaps
+ * @exp_info:		information needed to register this heap
+ */
+struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info);
+
+#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 000000000000..6ce5cc68d238
--- /dev/null
+++ b/include/uapi/linux/dma-heap.h
@@ -0,0 +1,55 @@ 
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * 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
+ */
+
+/* Valid FD_FLAGS are O_CLOEXEC, O_RDONLY, O_WRONLY, O_RDWR */
+#define DMA_HEAP_VALID_FD_FLAGS (O_CLOEXEC | O_ACCMODE)
+
+/* Currently no heap flags */
+#define DMA_HEAP_VALID_HEAP_FLAGS (0)
+
+/**
+ * struct dma_heap_allocation_data - metadata passed from userspace for
+ *                                      allocations
+ * @len:		size of the allocation
+ * @fd:			will be populated with a fd which provdes the
+ *			handle to the allocated dma-buf
+ * @fd_flags:		file descriptor flags used when allocating
+ * @heap_flags:		flags passed to heap
+ *
+ * Provided by userspace as an argument to the ioctl
+ */
+struct dma_heap_allocation_data {
+	__u64 len;
+	__u32 fd;
+	__u32 fd_flags;
+	__u64 heap_flags;
+	__u32 reserved0;
+	__u32 reserved1;
+};
+
+#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 */

Comments

Hi John,

On Fri, Oct 18, 2019 at 05:23:19AM +0000, John Stultz wrote:
> From: "Andrew F. Davis" <afd@ti.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@redhat.com>
> Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> Cc: Liam Mark <lmark@codeaurora.org>
> Cc: Pratik Patel <pratikp@codeaurora.org>
> Cc: Brian Starkey <Brian.Starkey@arm.com>
> Cc: Vincent Donnefort <Vincent.Donnefort@arm.com>
> Cc: Sudipto Paul <Sudipto.Paul@arm.com>
> Cc: Andrew F. Davis <afd@ti.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Chenbo Feng <fengc@google.com>
> Cc: Alistair Strachan <astrachan@google.com>
> Cc: Hridya Valsaraju <hridya@google.com>
> Cc: Hillf Danton <hdanton@sina.com>
> Cc: dri-devel@lists.freedesktop.org
> Reviewed-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Reviewed-by: Brian Starkey <brian.starkey@arm.com>
> Acked-by: Laura Abbott <labbott@redhat.com>
> Tested-by: Ayan Kumar Halder <ayan.halder@arm.com>
> Signed-off-by: Andrew F. Davis <afd@ti.com>
> Signed-off-by: John Stultz <john.stultz@linaro.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 than a buffer
>   (as it simplifies error handling)
> v3:
> * Removed scare-quotes in MAINTAINERS email address
> * Get rid of .release function as it didn't do anything (from
>   Christoph)
> * Renamed filp to file (suggested by Christoph)
> * Split out ioctl handling to separate function (suggested by
>   Christoph)
> * Add comment documenting PAGE_ALIGN usage (suggested by Brian)
> * Switch from idr to Xarray (suggested by Brian)
> * Fixup cdev creation (suggested by Brian)
> * Avoid EXPORT_SYMBOL until we finalize modules (suggested by
>   Brian)
> * Make struct dma_heap internal only (folded in from Andrew)
> * Small cleanups suggested by GregKH
> * Provide class->devnode callback to get consistent /dev/
>   subdirectory naming (Suggested by Bjorn)
> v4:
> * Folded down dma-heap.h change that was in a following patch
> * Added fd_flags entry to allocation structure and pass it
>   through to heap code for use on dma-buf fd creation (suggested
>   by Benjamin)
> v5:
> * Minor cleanups
> v6:
> * Improved error path handling, minor whitespace fixes, both
>   suggested by Brian
> v7:
> * Longer Kconfig description to quiet checkpatch warnings
> * Re-add compat_ioctl bits (Hridya noticed 32bit userland wasn't
>   working)
> v8:
> * Make struct dma_heap_ops consts (Suggested by Christoph)
> * Checkpatch whitespace fixups
> v9:
> * Minor cleanups suggested by Brian Starkey
> * Rename dma_heap_get_data->dma_heap_get_drvdata suggested
>   by Hilf Danton
> v11:
> * Kconfig text improvements suggested by Randy Dunlap
> v12:
> * Add logic to prevent duplicately named heaps being added
> * Add symbol exports for heaps as modules

As in v3:

 * Avoid EXPORT_SYMBOL until we finalize modules (suggested by
   Brian)

Did something change in that regard? I still think letting modules
register heaps without a way to remove them is a recipe for issues.

Thanks,
-Brian
On Fri, Oct 18, 2019 at 4:18 AM Brian Starkey <Brian.Starkey@arm.com> wrote:
> On Fri, Oct 18, 2019 at 05:23:19AM +0000, John Stultz wrote:
>
> As in v3:
>
>  * Avoid EXPORT_SYMBOL until we finalize modules (suggested by
>    Brian)

Heh. I guess it has been awhile.  :)

> Did something change in that regard? I still think letting modules
> register heaps without a way to remove them is a recipe for issues.

So yea, in recent months, work around Android with their GKI effort
has made it necessary for ION heaps to be loadable from modules. I had
some patches in WIP tree to enable this, and in the rework I did
yesterday for the CMA module trivially collided with parts, and
forgetting the discussion back in v3, I figured I'd just fold those
bits in before I resubmitted for v12.

If it's an issue, I can pull it out, but I'm going to be submitting
module enablement for review as soon as the core bits are queued, as
its going to be important to support for Android to switch to this
from ION.

thanks
-john
On Fri, Oct 18, 2019 at 11:26:52AM -0700, John Stultz wrote:
> On Fri, Oct 18, 2019 at 4:18 AM Brian Starkey <Brian.Starkey@arm.com> wrote:
> > On Fri, Oct 18, 2019 at 05:23:19AM +0000, John Stultz wrote:
> >
> > As in v3:
> >
> >  * Avoid EXPORT_SYMBOL until we finalize modules (suggested by
> >    Brian)
> 
> Heh. I guess it has been awhile.  :)
> 
> > Did something change in that regard? I still think letting modules
> > register heaps without a way to remove them is a recipe for issues.
> 
> So yea, in recent months, work around Android with their GKI effort
> has made it necessary for ION heaps to be loadable from modules. I had
> some patches in WIP tree to enable this, and in the rework I did
> yesterday for the CMA module trivially collided with parts, and
> forgetting the discussion back in v3, I figured I'd just fold those
> bits in before I resubmitted for v12.

Ah yes, I can see that would be needed.

> 
> If it's an issue, I can pull it out, but I'm going to be submitting
> module enablement for review as soon as the core bits are queued, as
> its going to be important to support for Android to switch to this
> from ION.
> 

I don't know how to decide if it's an issue. My understanding is that
if you rmmod something which has exported buffers, various Bad Things
might happen; I believe including data leaks, corruption or crashing
the kernel. There's probably plenty of scope for that with dma-buf
exporters already, so it's not exactly "new" but it is a bit
unfortunate.

If "people" are OK with adding new code which has the same issue, then
I'm not going to make any more of a fuss, because perfection is the
enemy of progress. Perhaps an obvious comment pointing out the issue
would be prudent, though - as a reminder to people that add heaps from
their code (and wonder why there's no "dma_heap_remove" function).

Cheers,
-Brian

> thanks
> -john
On Mon, Oct 21, 2019 at 2:36 AM Brian Starkey <Brian.Starkey@arm.com> wrote:
> On Fri, Oct 18, 2019 at 11:26:52AM -0700, John Stultz wrote:
> > On Fri, Oct 18, 2019 at 4:18 AM Brian Starkey <Brian.Starkey@arm.com> wrote:
> > > On Fri, Oct 18, 2019 at 05:23:19AM +0000, John Stultz wrote:
> > >
> > > As in v3:
> > >
> > >  * Avoid EXPORT_SYMBOL until we finalize modules (suggested by
> > >    Brian)
> >
> > Heh. I guess it has been awhile.  :)
> >
> > > Did something change in that regard? I still think letting modules
> > > register heaps without a way to remove them is a recipe for issues.
> >
> > So yea, in recent months, work around Android with their GKI effort
> > has made it necessary for ION heaps to be loadable from modules. I had
> > some patches in WIP tree to enable this, and in the rework I did
> > yesterday for the CMA module trivially collided with parts, and
> > forgetting the discussion back in v3, I figured I'd just fold those
> > bits in before I resubmitted for v12.
>
> Ah yes, I can see that would be needed.
>
> >
> > If it's an issue, I can pull it out, but I'm going to be submitting
> > module enablement for review as soon as the core bits are queued, as
> > its going to be important to support for Android to switch to this
> > from ION.
> >
>
> I don't know how to decide if it's an issue. My understanding is that
> if you rmmod something which has exported buffers, various Bad Things
> might happen; I believe including data leaks, corruption or crashing
> the kernel. There's probably plenty of scope for that with dma-buf
> exporters already, so it's not exactly "new" but it is a bit
> unfortunate.
>
> If "people" are OK with adding new code which has the same issue, then
> I'm not going to make any more of a fuss, because perfection is the
> enemy of progress. Perhaps an obvious comment pointing out the issue
> would be prudent, though - as a reminder to people that add heaps from
> their code (and wonder why there's no "dma_heap_remove" function).

Eh. If I need to respin anyway, I'll just remove the exports for now.

It's really just my fault for getting impatient and trying to squeeze
some extra changes in.

I'll then submit the module enablement patches separately.

Thanks again for the review, I really appreciate your sharp eye!
-john