[PATCH 9/9] iosys_map: embed the is_iomem bit into the pointer.

[Thomas Zimmermann]

Hi

Am 22.05.25 um 08:52 schrieb Dave Airlie:
> From: Dave Airlie <airlied at redhat.com>
>
> This reduces this struct from 16 to 8 bytes, and it gets embedded
> into a lot of things.

IIRC this has been discussed before. Makes sense to me.

> Signed-off-by: Dave Airlie <airlied at redhat.com>
> ---
>   include/linux/iosys-map.h | 30 ++++++++----------------------
>   1 file changed, 8 insertions(+), 22 deletions(-)
>
> diff --git a/include/linux/iosys-map.h b/include/linux/iosys-map.h
> index a6c2cc9ca756..44479966ce24 100644
> --- a/include/linux/iosys-map.h
> +++ b/include/linux/iosys-map.h
> @@ -99,29 +99,27 @@
>    *	iosys_map_incr(&map, len); // go to first byte after the memcpy
>    */
>   
> +#define _IOSYS_MAP_IS_IOMEM 1

Two underscores would be preferable to me. And please use the BIT() 
macro to define this constant.

Best regards
Thomas

>   /**
>    * struct iosys_map - Pointer to IO/system memory
>    * @vaddr_iomem:	The buffer's address if in I/O memory
>    * @vaddr:		The buffer's address if in system memory
> - * @is_iomem:		True if the buffer is located in I/O memory, or false
> - *			otherwise.
>    */
>   struct iosys_map {
>   	union {
>   		void __iomem *_vaddr_iomem;
>   		void *_vaddr;
>   	};
> -	bool _is_iomem;
>   };
>   
>   static inline bool iosys_map_is_iomem(const struct iosys_map *map)
>   {
> -	return map->_is_iomem;
> +	return ((unsigned long)map->_vaddr) & _IOSYS_MAP_IS_IOMEM;
>   }
>   
>   static inline void __iomem *iosys_map_ioptr(const struct iosys_map *map)
>   {
> -	return map->_vaddr_iomem;
> +	return (void __iomem *)((unsigned long)map->_vaddr_iomem & ~_IOSYS_MAP_IS_IOMEM);

Macros for encoding and decoding the pointer+bit would be preferred. 
Jani seems to have helpers for that.

Best regards
Thomas

>   }
>   
>   static inline void *iosys_map_ptr(const struct iosys_map *map)
> @@ -136,7 +134,6 @@ static inline void *iosys_map_ptr(const struct iosys_map *map)
>   #define IOSYS_MAP_INIT_VADDR(vaddr_)	\
>   	{				\
>   		._vaddr = (vaddr_),	\
> -		._is_iomem = false,	\
>   	}
>   
>   /**
> @@ -145,8 +142,7 @@ static inline void *iosys_map_ptr(const struct iosys_map *map)
>    */
>   #define IOSYS_MAP_INIT_VADDR_IOMEM(vaddr_iomem_)	\
>   	{						\
> -		._vaddr_iomem = (vaddr_iomem_),		\
> -		._is_iomem = true,			\
> +		._vaddr_iomem = (void __iomem *)(((unsigned long)(vaddr_iomem_) | _IOSYS_MAP_IS_IOMEM)), \
>   	}
>   
>   /**
> @@ -198,7 +194,6 @@ static inline void *iosys_map_ptr(const struct iosys_map *map)
>   static inline void iosys_map_set_vaddr(struct iosys_map *map, void *vaddr)
>   {
>   	map->_vaddr = vaddr;
> -	map->_is_iomem = false;
>   }
>   
>   /**
> @@ -211,8 +206,7 @@ static inline void iosys_map_set_vaddr(struct iosys_map *map, void *vaddr)
>   static inline void iosys_map_set_vaddr_iomem(struct iosys_map *map,
>   					     void __iomem *vaddr_iomem)
>   {
> -	map->_vaddr_iomem = vaddr_iomem;
> -	map->_is_iomem = true;
> +	map->_vaddr_iomem = (void __iomem *)((unsigned long)vaddr_iomem | _IOSYS_MAP_IS_IOMEM);
>   }
>   
>   /**
> @@ -229,12 +223,9 @@ static inline void iosys_map_set_vaddr_iomem(struct iosys_map *map,
>   static inline bool iosys_map_is_equal(const struct iosys_map *lhs,
>   				      const struct iosys_map *rhs)
>   {
> -	if (lhs->_is_iomem != rhs->_is_iomem)
> +	if (lhs->_vaddr != rhs->_vaddr)
>   		return false;
> -	else if (lhs->_is_iomem)
> -		return lhs->_vaddr_iomem == rhs->_vaddr_iomem;
> -	else
> -		return lhs->_vaddr == rhs->_vaddr;
> +	return true;
>   }
>   
>   /**
> @@ -279,12 +270,7 @@ static inline bool iosys_map_is_set(const struct iosys_map *map)
>    */
>   static inline void iosys_map_clear(struct iosys_map *map)
>   {
> -	if (map->_is_iomem) {
> -		map->_vaddr_iomem = NULL;
> -		map->_is_iomem = false;
> -	} else {
> -		map->_vaddr = NULL;
> -	}
> +	map->_vaddr = NULL;
>   }
>   
>   /**

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)