[RFC 3/6] dma-buf: Support generic userspace allocations
Noralf Trønnes
noralf at tronnes.org
Wed Jan 4 13:34:39 UTC 2017
Add a generic way for userspace to allocate dma-buf's for SPI transfers.
Signed-off-by: Noralf Trønnes <noralf at tronnes.org>
---
drivers/dma-buf/Makefile | 2 +-
drivers/dma-buf/dev.c | 211 +++++++++++++++++++++++++++++++++++++++
include/uapi/linux/dma-buf-dev.h | 35 +++++++
3 files changed, 247 insertions(+), 1 deletion(-)
create mode 100644 drivers/dma-buf/dev.c
create mode 100644 include/uapi/linux/dma-buf-dev.h
diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile
index 210a10b..ec867f7 100644
--- a/drivers/dma-buf/Makefile
+++ b/drivers/dma-buf/Makefile
@@ -1,3 +1,3 @@
-obj-y := dma-buf.o fence.o reservation.o seqno-fence.o fence-array.o
+obj-y := dma-buf.o fence.o reservation.o seqno-fence.o fence-array.o dev.o
obj-$(CONFIG_SYNC_FILE) += sync_file.o
obj-$(CONFIG_SW_SYNC) += sw_sync.o sync_debug.o
diff --git a/drivers/dma-buf/dev.c b/drivers/dma-buf/dev.c
new file mode 100644
index 0000000..536d9bf
--- /dev/null
+++ b/drivers/dma-buf/dev.c
@@ -0,0 +1,211 @@
+/*
+ * Copyright (C) 2016 Noralf Trønnes
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#include <uapi/linux/dma-buf-dev.h>
+
+struct dma_buf_dev_object {
+ struct device *dev;
+ unsigned long attrs;
+ dma_addr_t dma_addr;
+ void *vaddr;
+ size_t size;
+};
+
+static struct sg_table *
+dma_buf_dev_map_dma_buf(struct dma_buf_attachment *attach,
+ enum dma_data_direction dir)
+{
+ struct dma_buf_dev_object *obj = attach->dmabuf->priv;
+ struct sg_table *sgt;
+ int ret;
+
+ sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
+ if (!sgt)
+ return ERR_PTR(-ENOMEM);
+
+ ret = dma_get_sgtable(obj->dev, sgt, obj->vaddr,
+ obj->dma_addr, obj->size);
+ if (ret < 0)
+ goto err_free;
+
+ if (!dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir)) {
+ ret = -ENOMEM;
+ goto err_free_table;
+ }
+
+ return sgt;
+
+err_free_table:
+ sg_free_table(sgt);
+err_free:
+ kfree(sgt);
+
+ return ERR_PTR(ret);
+}
+
+static void dma_buf_dev_unmap_dma_buf(struct dma_buf_attachment *attach,
+ struct sg_table *sgt,
+ enum dma_data_direction dir)
+{
+ dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, dir);
+ sg_free_table(sgt);
+ kfree(sgt);
+}
+
+static void dma_buf_dev_release(struct dma_buf *dma_buf)
+{
+ struct dma_buf_dev_object *obj = dma_buf->priv;
+
+/* FIXME remove */
+pr_info("%s()\n", __func__);
+ dma_free_attrs(obj->dev, obj->size, obj->vaddr, obj->dma_addr,
+ obj->attrs);
+ kfree(obj);
+}
+
+static void *dma_buf_dev_kmap(struct dma_buf *dma_buf, unsigned long page_num)
+{
+ struct dma_buf_dev_object *obj = dma_buf->priv;
+
+ return obj->vaddr + page_num * PAGE_SIZE;
+}
+
+static void *dma_buf_dev_vmap(struct dma_buf *dma_buf)
+{
+ struct dma_buf_dev_object *obj = dma_buf->priv;
+
+ return obj->vaddr;
+}
+
+static int dma_buf_dev_mmap(struct dma_buf *dma_buf,
+ struct vm_area_struct *vma)
+{
+ struct dma_buf_dev_object *obj = dma_buf->priv;
+ int ret;
+
+ vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
+
+ ret = dma_mmap_attrs(obj->dev, vma, obj->vaddr, obj->dma_addr,
+ vma->vm_end - vma->vm_start, obj->attrs);
+
+ return ret;
+}
+
+static const struct dma_buf_ops dma_buf_dev_ops = {
+ .map_dma_buf = dma_buf_dev_map_dma_buf,
+ .unmap_dma_buf = dma_buf_dev_unmap_dma_buf,
+ .release = dma_buf_dev_release,
+ .kmap_atomic = dma_buf_dev_kmap,
+ .kmap = dma_buf_dev_kmap,
+ .vmap = dma_buf_dev_vmap,
+ .mmap = dma_buf_dev_mmap,
+};
+
+struct dma_buf *dma_buf_dev_alloc_attrs(struct device *dev, size_t size,
+ unsigned long attrs, int flags)
+{
+ DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+ struct dma_buf_dev_object *obj;
+ struct dma_buf *dmabuf;
+ int ret;
+
+ if (flags & ~(O_CLOEXEC | O_ACCMODE))
+ return ERR_PTR(-EINVAL);
+
+ obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+ if (!obj)
+ return ERR_PTR(-ENOMEM);
+
+ obj->dev = dev;
+ obj->size = size;
+ obj->attrs = attrs;
+
+ obj->vaddr = dma_alloc_attrs(dev, size, &obj->dma_addr, GFP_KERNEL, attrs);
+ if (!obj->vaddr) {
+ ret = -ENOMEM;
+ goto err_free_obj;
+ }
+
+ exp_info.ops = &dma_buf_dev_ops;
+ exp_info.size = obj->size;
+ exp_info.flags = flags;
+ exp_info.priv = obj;
+
+ dmabuf = dma_buf_export(&exp_info);
+ if (IS_ERR(dmabuf)) {
+ ret = PTR_ERR(dmabuf);
+ goto err_free_buf;
+ }
+
+ return dmabuf;
+
+err_free_buf:
+ dma_free_attrs(dev, size, obj->vaddr, obj->dma_addr, attrs);
+err_free_obj:
+ kfree(obj);
+
+ return ERR_PTR(ret);
+}
+
+static long dma_buf_dev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ struct dma_buf_dev_create create;
+ struct dma_buf *dmabuf;
+
+ switch (cmd) {
+ case DMA_BUF_DEV_IOCTL_CREATE:
+
+ if (copy_from_user(&create, (void __user *)arg, sizeof(create)))
+ return -EFAULT;
+
+ if (!create.size)
+ return -EINVAL;
+
+ dmabuf = dma_buf_dev_alloc_attrs(NULL, create.size,
+ create.attrs, create.flags);
+ if (IS_ERR(dmabuf))
+ return PTR_ERR(dmabuf);
+
+ create.fd = dma_buf_fd(dmabuf, create.flags);
+ if (create.fd < 0) {
+ dma_buf_put(dmabuf);
+ return create.fd;
+ }
+
+ if (copy_to_user((void __user *)arg, &create, sizeof(create)))
+ return -EFAULT;
+
+ return 0;
+ default:
+ return -ENOTTY;
+ }
+}
+
+static const struct file_operations dma_buf_dev_fops = {
+ .owner = THIS_MODULE,
+ .unlocked_ioctl = dma_buf_dev_ioctl,
+ .compat_ioctl = dma_buf_dev_ioctl,
+};
+
+static struct miscdevice dma_buf_dev_misc = {
+ .fops = &dma_buf_dev_fops,
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "dma-buf",
+};
+module_misc_device(dma_buf_dev_misc);
+
+MODULE_AUTHOR("Noralf Trønnes");
+MODULE_DESCRIPTION("User mode dma-buf creation");
+MODULE_LICENSE("GPL");
diff --git a/include/uapi/linux/dma-buf-dev.h b/include/uapi/linux/dma-buf-dev.h
new file mode 100644
index 0000000..fddbe04
--- /dev/null
+++ b/include/uapi/linux/dma-buf-dev.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2016 Noralf Trønnes
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef _DMA_BUF_DEV_UAPI_H_
+#define _DMA_BUF_DEV_UAPI_H_
+
+#include <linux/types.h>
+
+/**
+ * struct dma_buf_dev_create -
+ * @attrs: Attributes of mapping properties requested in dma_alloc_attrs
+ * @size: Buffer size
+ * @flags: Mode flags for the dma-buf file
+ * @fd: Returned dma-buf file descriptor
+ */
+struct dma_buf_dev_create {
+ __u64 attrs;
+#define DMA_BUF_DEV_ATTR_WRITE_COMBINE BIT(2)
+ __u64 size;
+ __u64 flags;
+
+ __s64 fd;
+};
+
+/* FIXME: Update Documentation/ioctl/ioctl-number.txt */
+#define DMA_BUF_DEV_BASE 0xB6
+#define DMA_BUF_DEV_IOCTL_CREATE _IOWR(DMA_BUF_DEV_BASE, 0, struct dma_buf_dev_create)
+
+#endif
--
2.10.2
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