Re: [PATCH 3/5] io-mapping: Always create a struct to hold metadata about the io-mapping

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

On ti, 2015-04-07 at 17:31 +0100, Chris Wilson wrote:
> Currently, we only allocate a structure to hold metadata if we need to
> allocate an ioremap for every access, such as on x86-32. However, it
> would be useful to store basic information about the io-mapping, such as
> its page protection, on all platforms.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

> Cc: linux-mm@kvack.org
> ---
>  include/linux/io-mapping.h | 52 ++++++++++++++++++++++++++++------------------
>  1 file changed, 32 insertions(+), 20 deletions(-)
> 
> diff --git a/include/linux/io-mapping.h b/include/linux/io-mapping.h
> index 657fab4efab3..e053011f50bb 100644
> --- a/include/linux/io-mapping.h
> +++ b/include/linux/io-mapping.h
> @@ -31,16 +31,17 @@
>   * See Documentation/io-mapping.txt
>   */
>  
> -#ifdef CONFIG_HAVE_ATOMIC_IOMAP
> -
> -#include <asm/iomap.h>
> -
>  struct io_mapping {
>  	resource_size_t base;
>  	unsigned long size;
>  	pgprot_t prot;
> +	void __iomem *iomem;
>  };
>  
> +
> +#ifdef CONFIG_HAVE_ATOMIC_IOMAP
> +
> +#include <asm/iomap.h>
>  /*
>   * For small address space machines, mapping large objects
>   * into the kernel virtual space isn't practical. Where
> @@ -119,48 +120,59 @@ io_mapping_unmap(void __iomem *vaddr)
>  #else
>  
>  #include <linux/uaccess.h>
> -
> -/* this struct isn't actually defined anywhere */
> -struct io_mapping;
> +#include <asm/pgtable_types.h>
>  
>  /* Create the io_mapping object*/
>  static inline struct io_mapping *
>  io_mapping_create_wc(resource_size_t base, unsigned long size)
>  {
> -	return (struct io_mapping __force *) ioremap_wc(base, size);
> +	struct io_mapping *iomap;
> +
> +	iomap = kmalloc(sizeof(*iomap), GFP_KERNEL);
> +	if (!iomap)
> +		return NULL;
> +
> +	iomap->base = base;
> +	iomap->size = size;
> +	iomap->iomem = ioremap_wc(base, size);
> +	iomap->prot = pgprot_writecombine(PAGE_KERNEL_IO);
> +
> +	return iomap;
>  }
>  
>  static inline void
>  io_mapping_free(struct io_mapping *mapping)
>  {
> -	iounmap((void __force __iomem *) mapping);
> +	iounmap(mapping->iomem);
> +	kfree(mapping);
>  }
>  
> -/* Atomic map/unmap */
> +/* Non-atomic map/unmap */
>  static inline void __iomem *
> -io_mapping_map_atomic_wc(struct io_mapping *mapping,
> -			 unsigned long offset)
> +io_mapping_map_wc(struct io_mapping *mapping, unsigned long offset)
>  {
> -	pagefault_disable();
> -	return ((char __force __iomem *) mapping) + offset;
> +	return mapping->iomem + offset;
>  }
>  
>  static inline void
> -io_mapping_unmap_atomic(void __iomem *vaddr)
> +io_mapping_unmap(void __iomem *vaddr)
>  {
> -	pagefault_enable();
>  }
>  
> -/* Non-atomic map/unmap */
> +/* Atomic map/unmap */
>  static inline void __iomem *
> -io_mapping_map_wc(struct io_mapping *mapping, unsigned long offset)
> +io_mapping_map_atomic_wc(struct io_mapping *mapping,
> +			 unsigned long offset)
>  {
> -	return ((char __force __iomem *) mapping) + offset;
> +	pagefault_disable();
> +	return io_mapping_map_wc(mapping, offset);
>  }
>  
>  static inline void
> -io_mapping_unmap(void __iomem *vaddr)
> +io_mapping_unmap_atomic(void __iomem *vaddr)
>  {
> +	io_mapping_unmap(vaddr);
> +	pagefault_enable();
>  }
>  
>  #endif /* HAVE_ATOMIC_IOMAP */


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