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SubjectRe: [PATCH 3/4] videobuf2-dma-streaming: new videobuf2 memory allocator
Date
On Thu 13 September 2012 15:52:47 Federico Vaga wrote:
> Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
> ---
> drivers/media/v4l2-core/Kconfig | 5 +
> drivers/media/v4l2-core/Makefile | 1 +
> drivers/media/v4l2-core/videobuf2-dma-streaming.c | 205 ++++++++++++++++++++++
> include/media/videobuf2-dma-streaming.h | 24 +++
> 4 file modificati, 235 inserzioni(+)
> create mode 100644 drivers/media/v4l2-core/videobuf2-dma-streaming.c
> create mode 100644 include/media/videobuf2-dma-streaming.h
>
> diff --git a/drivers/media/v4l2-core/Kconfig b/drivers/media/v4l2-core/Kconfig
> index 0c54e19..60548a7 100644
> --- a/drivers/media/v4l2-core/Kconfig
> +++ b/drivers/media/v4l2-core/Kconfig
> @@ -79,3 +79,8 @@ config VIDEOBUF2_DMA_SG
> #depends on HAS_DMA
> select VIDEOBUF2_CORE
> select VIDEOBUF2_MEMOPS
> +
> +config VIDEOBUF2_DMA_STREAMING
> + select VIDEOBUF2_CORE
> + select VIDEOBUF2_MEMOPS
> + tristate
> diff --git a/drivers/media/v4l2-core/Makefile b/drivers/media/v4l2-core/Makefile
> index c2d61d4..0b2756f 100644
> --- a/drivers/media/v4l2-core/Makefile
> +++ b/drivers/media/v4l2-core/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_VIDEOBUF2_MEMOPS) += videobuf2-memops.o
> obj-$(CONFIG_VIDEOBUF2_VMALLOC) += videobuf2-vmalloc.o
> obj-$(CONFIG_VIDEOBUF2_DMA_CONTIG) += videobuf2-dma-contig.o
> obj-$(CONFIG_VIDEOBUF2_DMA_SG) += videobuf2-dma-sg.o
> +obj-$(CONFIG_VIDEOBUF2_DMA_STREAMING) += videobuf2-dma-streaming.o
>
> ccflags-y += -I$(srctree)/drivers/media/dvb-core
> ccflags-y += -I$(srctree)/drivers/media/dvb-frontends
> diff --git a/drivers/media/v4l2-core/videobuf2-dma-streaming.c b/drivers/media/v4l2-core/videobuf2-dma-streaming.c
> new file mode 100644
> index 0000000..23475a6
> --- /dev/null
> +++ b/drivers/media/v4l2-core/videobuf2-dma-streaming.c
> @@ -0,0 +1,205 @@
> +/*
> + * videobuf2-dma-streaming.c - DMA streaming memory allocator for videobuf2
> + *
> + * Copyright (C) 2012 Federico Vaga <federico.vaga@gmail.com>
> + * *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/pagemap.h>
> +#include <linux/dma-mapping.h>
> +
> +#include <media/videobuf2-core.h>
> +#include <media/videobuf2-dma-streaming.h>
> +#include <media/videobuf2-memops.h>
> +
> +struct vb2_streaming_conf {
> + struct device *dev;
> +};
> +struct vb2_streaming_buf {
> + struct vb2_streaming_conf *conf;
> + void *vaddr;
> +
> + dma_addr_t dma_handle;
> +
> + unsigned long size;
> + struct vm_area_struct *vma;
> +
> + atomic_t refcount;
> + struct vb2_vmarea_handler handler;
> +};
> +
> +static void vb2_dma_streaming_put(void *buf_priv)
> +{
> + struct vb2_streaming_buf *buf = buf_priv;
> +
> + if (atomic_dec_and_test(&buf->refcount)) {
> + dma_unmap_single(buf->conf->dev, buf->dma_handle, buf->size,
> + DMA_FROM_DEVICE);
> + free_pages_exact(buf->vaddr, buf->size);
> + kfree(buf);
> + }
> +
> +}
> +
> +static void *vb2_dma_streaming_alloc(void *alloc_ctx, unsigned long size)
> +{
> + struct vb2_streaming_conf *conf = alloc_ctx;
> + struct vb2_streaming_buf *buf;
> + int err;
> +
> + buf = kzalloc(sizeof *buf, GFP_KERNEL);
> + if (!buf)
> + return ERR_PTR(-ENOMEM);
> + buf->vaddr = alloc_pages_exact(size, GFP_KERNEL | GFP_DMA);
> + if (!buf->vaddr) {
> + err = -ENOMEM;
> + goto out;
> + }
> + buf->dma_handle = dma_map_single(conf->dev, buf->vaddr, size,
> + DMA_FROM_DEVICE);
> + err = dma_mapping_error(conf->dev, buf->dma_handle);
> + if (err) {
> + dev_err(conf->dev, "dma_map_single failed\n");
> +
> + free_pages_exact(buf->vaddr, size);
> + buf->vaddr = NULL;
> + goto out_pages;
> + }
> + buf->conf = conf;
> + buf->size = size;
> + buf->handler.refcount = &buf->refcount;
> + buf->handler.put = vb2_dma_streaming_put;
> + buf->handler.arg = buf;
> +
> + atomic_inc(&buf->refcount);
> + return buf;
> +
> +out_pages:
> + free_pages_exact(buf->vaddr, buf->size);
> +out:
> + kfree(buf);
> + return ERR_PTR(err);
> +}
> +
> +static void *vb2_dma_streaming_cookie(void *buf_priv)
> +{
> + struct vb2_streaming_buf *buf = buf_priv;
> +
> + return (void *)buf->dma_handle;
> +}
> +
> +static void *vb2_dma_streaming_vaddr(void *buf_priv)
> +{
> + struct vb2_streaming_buf *buf = buf_priv;
> +
> + if (!buf)
> + return NULL;
> + return buf->vaddr;
> +}
> +
> +static unsigned int vb2_dma_streaming_num_users(void *buf_priv)
> +{
> + struct vb2_streaming_buf *buf = buf_priv;
> +
> + return atomic_read(&buf->refcount);
> +}
> +
> +static int vb2_dma_streaming_mmap(void *buf_priv, struct vm_area_struct *vma)
> +{
> + struct vb2_streaming_buf *buf = buf_priv;
> + unsigned long pos, start = vma->vm_start;
> + unsigned long size;
> + struct page *page;
> + int err;
> +
> + /* Try to remap memory */
> + size = vma->vm_end - vma->vm_start;
> + size = (size < buf->size) ? size : buf->size;
> + pos = (unsigned long)buf->vaddr;
> +
> + while (size > 0) {
> + page = virt_to_page((void *)pos);
> + if (!page) {
> + dev_err(buf->conf->dev, "mmap: virt_to_page failed\n");
> + return -ENOMEM;
> + }
> + err = vm_insert_page(vma, start, page);
> + if (err) {
> + dev_err(buf->conf->dev, "mmap: insert failed %d\n", err);
> + return -ENOMEM;
> + }
> + start += PAGE_SIZE;
> + pos += PAGE_SIZE;
> +
> + if (size > PAGE_SIZE)
> + size -= PAGE_SIZE;
> + else
> + size = 0;
> + }
> +
> +
> + vma->vm_ops = &vb2_common_vm_ops;
> + vma->vm_flags |= VM_DONTEXPAND;
> + vma->vm_private_data = &buf->handler;
> +
> + vma->vm_ops->open(vma);
> +
> + return 0;
> +}
> +
> +static void vb2_dma_streaming_prepare(void *buf_priv)
> +{
> + struct vb2_streaming_buf *buf = buf_priv;
> +
> + dma_sync_single_for_device(buf->conf->dev, buf->dma_handle,
> + buf->size, DMA_FROM_DEVICE);
> +}
> +
> +static void vb2_dma_streaming_finish(void *buf_priv)
> +{
> + struct vb2_streaming_buf *buf = buf_priv;
> +
> + dma_sync_single_for_cpu(buf->conf->dev, buf->dma_handle,
> + buf->size, DMA_FROM_DEVICE);
> +}
> +
> +const struct vb2_mem_ops vb2_dma_streaming_memops = {
> + .alloc = vb2_dma_streaming_alloc,
> + .put = vb2_dma_streaming_put,
> + .cookie = vb2_dma_streaming_cookie,
> + .vaddr = vb2_dma_streaming_vaddr,
> + .mmap = vb2_dma_streaming_mmap,
> + .num_users = vb2_dma_streaming_num_users,
> + .prepare = vb2_dma_streaming_prepare,
> + .finish = vb2_dma_streaming_finish,
> +};
> +EXPORT_SYMBOL_GPL(vb2_dma_streaming_memops);
> +
> +void *vb2_dma_streaming_init_ctx(struct device *dev)
> +{
> + struct vb2_streaming_conf *conf;
> +
> + conf = kmalloc(sizeof *conf, GFP_KERNEL);
> + if (!conf)
> + return ERR_PTR(-ENOMEM);
> +
> + conf->dev = dev;
> +
> + return conf;
> +}
> +EXPORT_SYMBOL_GPL(vb2_dma_streaming_init_ctx);
> +
> +void vb2_dma_streaming_cleanup_ctx(void *alloc_ctx)
> +{
> + kfree(alloc_ctx);
> +}
> +EXPORT_SYMBOL_GPL(vb2_dma_streaming_cleanup_ctx);
> +
> +MODULE_DESCRIPTION("DMA-streaming memory allocator for videobuf2");
> +MODULE_AUTHOR("Federico Vaga <federico.vaga@gmail.com>");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/media/videobuf2-dma-streaming.h b/include/media/videobuf2-dma-streaming.h
> new file mode 100644
> index 0000000..89cbd06
> --- /dev/null
> +++ b/include/media/videobuf2-dma-streaming.h
> @@ -0,0 +1,24 @@
> +/*
> + * videobuf2-dma-streaming.h - DMA steaming memory allocator for videobuf2

typo: steaming -> streaming :-)

The header and esp. the source could really do with more documentation. It is
not at all clear from the code what the dma-streaming allocator does and how
it differs from other allocators.

Regards,

Hans

> + *
> + * Copyright (C) 2012 Federico Vaga
> + *
> + * Author: Federico Vaga <federico.vaga@gmail.com>
> + *
> + * 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.
> + */
> +
> +#ifndef _MEDIA_VIDEOBUF2_DMA_STREAMING_H
> +#define _MEDIA_VIDEOBUF2_DMA_STREAMING_H
> +
> +#include <media/videobuf2-core.h>
> +#include <linux/dma-mapping.h>
> +
> +void *vb2_dma_streaming_init_ctx(struct device *dev);
> +void vb2_dma_streaming_cleanup_ctx(void *alloc_ctx);
> +
> +extern const struct vb2_mem_ops vb2_dma_streaming_memops;
> +
> +#endif
>


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