linux-kernel - Re: [RFC 2/3] of: reserved_mem: Accessor for acquiring reserved

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Date:   Mon, 24 Apr 2017 10:27:09 -0700
From:   Frank Rowand <frowand.list@...il.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 2/3] of: reserved_mem: Accessor for acquiring reserved_mem

On 04/22/17 10:35, Bjorn Andersson wrote:
> In some cases drivers referencing a reserved-memory region might want to
> remap the entire region, but when defining the reserved-memory by "size"
> the client driver has no means to know the associated base address of
> the reserved memory region.
> 
> This patch adds an accessor for such drivers to acquire a handle to
> their associated reserved-memory for this purpose.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
> 
> I would have preferred if we could provide a mechanism for drivers to find the
> reserved_mem of their own device_node, but without a phandle I have not been
> able to figure out a sane way to make the match.
> 
> Suggestions are very welcome.
> 
>  drivers/of/of_reserved_mem.c    | 26 ++++++++++++++++++++++++++
>  include/linux/of_reserved_mem.h |  8 ++++++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> index d507c3569a88..aa69c9590a5c 100644
> --- a/drivers/of/of_reserved_mem.c
> +++ b/drivers/of/of_reserved_mem.c
> @@ -397,3 +397,29 @@ void of_reserved_mem_device_release(struct device *dev)
>  	rmem->ops->device_release(rmem, dev);
>  }
>  EXPORT_SYMBOL_GPL(of_reserved_mem_device_release);
> +
> +/**
> + * of_get_reserved_mem_by_idx() - acquire reserved_mem from memory-region
> + * @np:		node pointer containing the "memory-region"
> + * @idx:	index within memory-region
> + *
> + * This function allows drivers to acquire a reference to the reserved_mem
> + * struct which is referenced by their memory-region.
> + *
> + * Returns a reserved_mem reference, or NULL on error.
> + */
> +struct reserved_mem *of_get_reserved_mem_by_idx(struct device_node *np, int idx)
> +{
> +	struct device_node *target;
> +	struct reserved_mem *rmem;
> +
> +	target = of_parse_phandle(np, "memory-region", idx);
> +	if (!target)
> +		return NULL;
> +
> +	rmem = __find_rmem(target);
> +	of_node_put(target);
> +
> +	return rmem;
> +}
> +EXPORT_SYMBOL_GPL(of_get_reserved_mem_by_idx);
> diff --git a/include/linux/of_reserved_mem.h b/include/linux/of_reserved_mem.h
> index f8e1992d6423..a9abbe7dd3de 100644
> --- a/include/linux/of_reserved_mem.h
> +++ b/include/linux/of_reserved_mem.h
> @@ -34,6 +34,8 @@ int of_reserved_mem_device_init_by_idx(struct device *dev,
>  				       struct device_node *np, int idx);
>  void of_reserved_mem_device_release(struct device *dev);
>  
> +struct reserved_mem *of_get_reserved_mem_by_idx(struct device_node *np, int idx);
> +
>  int early_init_dt_alloc_reserved_memory_arch(phys_addr_t size,
>  					     phys_addr_t align,
>  					     phys_addr_t start,
> @@ -52,6 +54,12 @@ static inline int of_reserved_mem_device_init_by_idx(struct device *dev,
>  }
>  static inline void of_reserved_mem_device_release(struct device *pdev) { }
>  
> +static inline struct reserved_mem *of_get_reserved_mem_by_idx(struct device_node *np,
> +							      int idx);
> +{
> +	return NULL;
> +}
> +
>  static inline void fdt_init_reserved_mem(void) { }
>  static inline void fdt_reserved_mem_save_node(unsigned long node,
>  		const char *uname, phys_addr_t base, phys_addr_t size) { }
> 

Reviewed-by: Frank Rowand <frank.rowand@...y.com>