Re: [PATCH v3 2/4] videobuf2-dma-streaming: new videobuf2 memoryallocator
From: Mauro Carvalho Chehab
Date: Tue Dec 04 2012 - 11:04:53 EST
Em 24-09-2012 09:44, Marek Szyprowski escreveu:
Hello,
On Monday, September 24, 2012 12:59 PM Federico Vaga wrote:
The DMA streaming allocator is similar to the DMA contig but it use the
DMA streaming interface (dma_map_single, dma_unmap_single). The
allocator allocates buffers and immediately map the memory for DMA
transfer. For each buffer prepare/finish it does a DMA synchronization.
Hmm.. the explanation didn't convince me, e. g.:
1) why is it needed;
2) why vb2-dma-config can't be patched to use dma_map_single
(eventually using a different vb2_io_modes bit?);
3) what are the usecases for it.
Could you please detail it? Without that, one that would be needing to
write a driver will have serious doubts about what would be the right
driver for its usage. Also, please document it at the driver itself.
Thanks!
Mauro
Signed-off-by: Federico Vaga <federico.vaga@xxxxxxxxx>
Acked-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
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 | 32 ++++
4 file modificati, 243 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..c839e05
--- /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@xxxxxxxxx>
+ *
+ * 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(struct vb2_streaming_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 &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(struct vb2_streaming_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@xxxxxxxxx>");
+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..2a62d93
--- /dev/null
+++ b/include/media/videobuf2-dma-streaming.h
@@ -0,0 +1,32 @@
+/*
+ * videobuf2-dma-streaming.h - DMA streaming memory allocator for videobuf2
+ *
+ * Copyright (C) 2012 Federico Vaga
+ *
+ * Author: Federico Vaga <federico.vaga@xxxxxxxxx>
+ *
+ * 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;
+
+static inline dma_addr_t
+vb2_dma_streaming_plane_paddr(struct vb2_buffer *vb, unsigned int plane_no)
+{
+ dma_addr_t *dma_addr = vb2_plane_cookie(vb, plane_no);
+
+ return *dma_addr;
+}
+
+#endif
--
1.7.11.4
Best regards
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