Re: [PATCH 1/1] Userspace I/O (UIO): Add support for userspace DMA

["Hans J. Koch" <hjk@linutronix.de>]

(Deleted hugh <hugh@veritas.com> from Cc:, this address has permanent errors.)

On Tue, Dec 15, 2009 at 09:47:34AM -0800, Earl Chew wrote:
> Earl Chew wrote:
> > I'd like to proceed by changing struct uio_mem [MAX_UIO_MAPS] to a
> > linked list.
> 
> Here's my first go at changing to a linked list. I mistakenly
> said that I would proceed by modifying struct uio_mem [MAX_UIO_MAPS].

NAK, for the reasons given in my other mail.

Thanks,
Hans

> 
> In fact, I think that mem[MAX_UIO_MAPS] in struct uio_info can remain
> intact -- thus preserving the client facing API.
> 
> The linked list change occurs in struct uio_device which is private
> to uio.c ... thus hiding the change from client facing code.
> 
> 
> Tying the regions into a linked list held by struct uio_device
> simplifies the search-modify code in the rest of uio.c.
> 
> 
> Earl
> 
> 
> diff -uNpw uio_driver.h.old uio_driver.h
> --- c:/tmp/makereview.AGgMh	2009-12-15 09:41:23.146608800 -0800
> +++ c:/tmp/makereview.oXYWW	2009-12-15 09:41:23.255983800 -0800
> @@ -20,6 +20,8 @@
>  
>  /**
>   * struct uio_mem - description of a UIO memory region
> + * @list_node:		list node for struct uio_device list
> + * @mapid:		mapping number for this region
>   * @kobj:		kobject for this mapping
>   * @addr:		address of the device's memory
>   * @size:		size of IO
> @@ -27,6 +29,8 @@
>   * @internal_addr:	ioremap-ped version of addr, for driver internal use
>   */
>  struct uio_mem {
> +        struct list_head        list_node;
> +        unsigned                map_id;
>  	struct kobject		kobj;
>  	unsigned long		addr;
>  	unsigned long		size;
> 
> diff -uNpw uio.c.old uio.c
> --- c:/tmp/makereview.O27Xv	2009-12-15 09:41:26.740358800 -0800
> +++ c:/tmp/makereview.DAhCY	2009-12-15 09:41:26.834108800 -0800
> @@ -35,6 +35,7 @@ struct uio_device {
>  	int			vma_count;
>  	struct uio_info		*info;
>  	struct kset 		map_attr_kset;
> +	struct list_head	mem_list;
>  };
>  
>  static int uio_major;
> @@ -153,7 +154,7 @@ static int uio_dev_add_attributes(struct
>  	if (ret)
>  		goto err_group;
>  
> -	for (mi = 0; mi < MAX_UIO_MAPS; mi++) {
> +	for (mi = 0; mi < ARRAY_SIZE(idev->info->mem); mi++) {
>  		mem = &idev->info->mem[mi];
>  		if (mem->size == 0)
>  			break;
> @@ -166,6 +167,12 @@ static int uio_dev_add_attributes(struct
>  			if (ret)
>  				goto err_remove_group;
>  		}
> +
> +		mem->map_id = mi;
> +
> +		INIT_LIST_HEAD(&mem->list_node);
> +		list_add(&mem->list_node, &idev->mem_list);
> +
>  		kobject_init(&mem->kobj);
>  		kobject_set_name(&mem->kobj,"map%d",mi);
>  		mem->kobj.parent = &idev->map_attr_kset.kobj;
> @@ -180,6 +187,7 @@ static int uio_dev_add_attributes(struct
>  err_remove_maps:
>  	for (mi--; mi>=0; mi--) {
>  		mem = &idev->info->mem[mi];
> +		list_del(&mem->list_node);
>  		kobject_unregister(&mem->kobj);
>  	}
>  	kset_unregister(&idev->map_attr_kset); /* Needed ? */
> @@ -194,10 +202,11 @@ static void uio_dev_del_attributes(struc
>  {
>  	int mi;
>  	struct uio_mem *mem;
> -	for (mi = 0; mi < MAX_UIO_MAPS; mi++) {
> +	for (mi = 0; mi < ARRAY_SIZE(idev->info->mem); mi++) {
>  		mem = &idev->info->mem[mi];
>  		if (mem->size == 0)
>  			break;
> +		list_del(&mem->list_node);
>  		kobject_unregister(&mem->kobj);
>  	}
>  	kset_unregister(&idev->map_attr_kset);
> @@ -386,18 +395,20 @@ static ssize_t uio_read(struct file *fil
>  	return retval;
>  }
>  
> -static int uio_find_mem_index(struct vm_area_struct *vma)
> +static struct uio_mem *uio_find_mem_index(struct vm_area_struct *vma)
>  {
> -	int mi;
>  	struct uio_device *idev = vma->vm_private_data;
> +	struct list_head *mem_list;
> +
> +	list_for_each(mem_list, &idev->mem_list) {
>  
> -	for (mi = 0; mi < MAX_UIO_MAPS; mi++) {
> -		if (idev->info->mem[mi].size == 0)
> -			return -1;
> -		if (vma->vm_pgoff == mi)
> -			return mi;
> +		struct uio_mem *mem =
> +			list_entry(mem_list, struct uio_mem, list_node);
> +
> +		if (vma->vm_pgoff == mem->map_id)
> +			return mem;
>  	}
> -	return -1;
> +	return NULL;
>  }
>  
>  static void uio_vma_open(struct vm_area_struct *vma)
> @@ -415,17 +426,16 @@ static void uio_vma_close(struct vm_area
>  static struct page *uio_vma_nopage(struct vm_area_struct *vma,
>  				   unsigned long address, int *type)
>  {
> -	struct uio_device *idev = vma->vm_private_data;
>  	struct page* page = NOPAGE_SIGBUS;
>  
> -	int mi = uio_find_mem_index(vma);
> -	if (mi < 0)
> +	struct uio_mem *mem = uio_find_mem_index(vma);
> +	if (mem == NULL)
>  		return page;
>  
> -	if (idev->info->mem[mi].memtype == UIO_MEM_LOGICAL)
> -		page = virt_to_page(idev->info->mem[mi].addr);
> +	if (mem->memtype == UIO_MEM_LOGICAL)
> +		page = virt_to_page(mem->addr);
>  	else
> -		page = vmalloc_to_page((void*)idev->info->mem[mi].addr);
> +		page = vmalloc_to_page((void*)mem->addr);
>  	get_page(page);
>  	if (type)
>  		*type = VM_FAULT_MINOR;
> @@ -440,16 +450,15 @@ static struct vm_operations_struct uio_v
>  
>  static int uio_mmap_physical(struct vm_area_struct *vma)
>  {
> -	struct uio_device *idev = vma->vm_private_data;
> -	int mi = uio_find_mem_index(vma);
> -	if (mi < 0)
> +	struct uio_mem *mem = uio_find_mem_index(vma);
> +	if (mem == NULL)
>  		return -EINVAL;
>  
>  	vma->vm_flags |= VM_IO | VM_RESERVED;
>  
>  	return remap_pfn_range(vma,
>  			       vma->vm_start,
> -			       idev->info->mem[mi].addr >> PAGE_SHIFT,
> +			       mem->addr >> PAGE_SHIFT,
>  			       vma->vm_end - vma->vm_start,
>  			       vma->vm_page_prot);
>  }
> @@ -466,7 +475,7 @@ static int uio_mmap(struct file *filep, 
>  {
>  	struct uio_listener *listener = filep->private_data;
>  	struct uio_device *idev = listener->dev;
> -	int mi;
> +	struct uio_mem *mem;
>  	unsigned long requested_pages, actual_pages;
>  	int ret = 0;
>  
> @@ -475,12 +484,12 @@ static int uio_mmap(struct file *filep, 
>  
>  	vma->vm_private_data = idev;
>  
> -	mi = uio_find_mem_index(vma);
> -	if (mi < 0)
> +	mem = uio_find_mem_index(vma);
> +	if (mem == NULL)
>  		return -EINVAL;
>  
>  	requested_pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
> -	actual_pages = (idev->info->mem[mi].size + PAGE_SIZE -1) >> PAGE_SHIFT;
> +	actual_pages = (mem->size + PAGE_SIZE -1) >> PAGE_SHIFT;
>  	if (requested_pages > actual_pages)
>  		return -EINVAL;
>  
> @@ -492,7 +501,7 @@ static int uio_mmap(struct file *filep, 
>  		return ret;
>  	}
>  
> -	switch (idev->info->mem[mi].memtype) {
> +	switch (mem->memtype) {
>  		case UIO_MEM_PHYS:
>  			return uio_mmap_physical(vma);
>  		case UIO_MEM_LOGICAL:
> @@ -613,6 +622,7 @@ int __uio_register_device(struct module 
>  	idev->info = info;
>  	init_waitqueue_head(&idev->wait);
>  	atomic_set(&idev->event, 0);
> +	INIT_LIST_HEAD(&idev->mem_list);
>  
>  	ret = uio_get_minor(idev);
>  	if (ret)
> 

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