linux-kernel - Re: [PATCH] firmware: qcom_scm: fix error for incompatible pointer

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Message-ID: <7ea51e42-ab8a-e4e2-1833-651e2dabca3c@free.fr>
Date:   Mon, 22 Jul 2019 10:38:55 +0200
From:   Marc Gonzalez <marc.w.gonzalez@...e.fr>
To:     Minwoo Im <minwoo.im.dev@...il.com>,
        MSM <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stanimir Varbanov <svarbanov@...sol.com>,
        Rob Clark <robdclark@...il.com>,
        Stephen Boyd <sboyd@...nel.org>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] firmware: qcom_scm: fix error for incompatible pointer

Adding people who have worked on drivers/firmware/qcom_scm.c or DMA

On 19/07/2019 15:43, Minwoo Im wrote:

> The following error can happen when trying to build it:
> 
> ```
> drivers/firmware/qcom_scm.c: In function ‘qcom_scm_assign_mem’:
> drivers/firmware/qcom_scm.c:460:47: error: passing argument 3 of ‘dma_alloc_coherent’ from incompatible pointer type [-Werror=incompatible-pointer-types]
>   ptr = dma_alloc_coherent(__scm->dev, ptr_sz, &ptr_phys, GFP_KERNEL);
>                                                ^
> In file included from drivers/firmware/qcom_scm.c:12:0:
> ./include/linux/dma-mapping.h:636:21: note: expected ‘dma_addr_t * {aka long long unsigned int *}’ but argument is of type ‘phys_addr_t * {aka unsigned int *}’
>  static inline void *dma_alloc_coherent(struct device *dev, size_t size,
>                      ^~~~~~~~~~~~~~~~~~
> ```
> 
> We just can cast phys_addr_t to dma_addr_t here.

IME, casting is rarely a proper solution.


> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> index 2ddc118dba1b..7f6c841fa200 100644
> --- a/drivers/firmware/qcom_scm.c
> +++ b/drivers/firmware/qcom_scm.c
> @@ -457,7 +457,8 @@ int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t mem_sz,
>  	ptr_sz = ALIGN(src_sz, SZ_64) + ALIGN(mem_to_map_sz, SZ_64) +
>  			ALIGN(dest_sz, SZ_64);
>  
> -	ptr = dma_alloc_coherent(__scm->dev, ptr_sz, &ptr_phys, GFP_KERNEL);
> +	ptr = dma_alloc_coherent(__scm->dev, ptr_sz, (dma_addr_t *) &ptr_phys,
> +					GFP_KERNEL);
>  	if (!ptr)
>  		return -ENOMEM;
>