Re: [PATCH v6 13/20] dma-direct: rename ret to cpu_addr in alloc helpers

[Petr Tesarik <ptesarik@suse.com>]

On Thu,  4 Jun 2026 14:09:52 +0530
"Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org> wrote:

> ret in dma_direct_alloc() and dma_direct_alloc_pages() holds the returned
> CPU mapping, not a generic return value. Rename it to cpu_addr and update
> the remaining uses to match.
> 
> This makes the allocation paths easier to follow and keeps the local naming
> consistent with what the variable actually represents.
> 
> Tested-by: Michael Kelley <mhklinux@outlook.com>
> Tested-by: Mostafa Saleh <smostafa@google.com>
> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>

I wondered if cpu_addr is descriptive enough (a CPU address could
theoretically be virtual or physical), but I can see that a few other
places already use cpu_addr to hold virtual addresses, so yeah, let's
keep this name.

Reviewed-by: Petr Tesarik <ptesarik@suse.com>

Petr T

> ---
>  kernel/dma/direct.c | 31 +++++++++++++++----------------
>  1 file changed, 15 insertions(+), 16 deletions(-)
> 
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index aa3489aa10a0..4e446aa4130e 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -204,7 +204,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
>  	bool mark_mem_decrypt = false;
>  	bool allow_highmem = true;
>  	struct page *page;
> -	void *ret;
> +	void *cpu_addr;
>  
>  	/*
>  	 * DMA_ATTR_CC_SHARED is not a caller-visible dma_alloc_*()
> @@ -318,34 +318,33 @@ void *dma_direct_alloc(struct device *dev, size_t size,
>  		arch_dma_prep_coherent(page, size);
>  
>  		/* create a coherent mapping */
> -		ret = dma_common_contiguous_remap(page, size, prot,
> -				__builtin_return_address(0));
> -		if (!ret)
> +		cpu_addr = dma_common_contiguous_remap(page, size, prot,
> +					__builtin_return_address(0));
> +		if (!cpu_addr)
>  			goto out_encrypt_pages;
>  	} else {
> -		ret = page_address(page);
> +		cpu_addr = page_address(page);
>  	}
>  
> -	memset(ret, 0, size);
> +	memset(cpu_addr, 0, size);
>  
>  	if (set_uncached) {
>  		void *uncached_cpu_addr;
>  
>  		arch_dma_prep_coherent(page, size);
> -		uncached_cpu_addr = arch_dma_set_uncached(ret, size);
> +		uncached_cpu_addr = arch_dma_set_uncached(cpu_addr, size);
>  		if (IS_ERR(uncached_cpu_addr))
>  			goto out_free_remap_pages;
> -		ret = uncached_cpu_addr;
> +		cpu_addr = uncached_cpu_addr;
>  	}
>  
>  	*dma_handle = phys_to_dma_direct(dev, page_to_phys(page),
>  					 !!(attrs & DMA_ATTR_CC_SHARED));
> -	return ret;
> -
> +	return cpu_addr;
>  
>  out_free_remap_pages:
>  	if (remap)
> -		dma_common_free_remap(ret, size);
> +		dma_common_free_remap(cpu_addr, size);
>  
>  out_encrypt_pages:
>  	if (mark_mem_decrypt &&
> @@ -439,7 +438,7 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size,
>  {
>  	unsigned long attrs = 0;
>  	struct page *page;
> -	void *ret;
> +	void *cpu_addr;
>  
>  	if (force_dma_unencrypted(dev))
>  		attrs |= DMA_ATTR_CC_SHARED;
> @@ -453,7 +452,7 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size,
>  		if (!page)
>  			return NULL;
>  
> -		ret = page_address(page);
> +		cpu_addr = page_address(page);
>  		goto setup_page;
>  	}
>  
> @@ -461,11 +460,11 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size,
>  	if (!page)
>  		return NULL;
>  
> -	ret = page_address(page);
> -	if ((attrs & DMA_ATTR_CC_SHARED) && dma_set_decrypted(dev, ret, size))
> +	cpu_addr = page_address(page);
> +	if ((attrs & DMA_ATTR_CC_SHARED) && dma_set_decrypted(dev, cpu_addr, size))
>  		goto out_leak_pages;
>  setup_page:
> -	memset(ret, 0, size);
> +	memset(cpu_addr, 0, size);
>  	*dma_handle = phys_to_dma_direct(dev, page_to_phys(page),
>  					 !!(attrs & DMA_ATTR_CC_SHARED));
>  	return page;