linux-kernel - Re: [PATCH 09/19] dma-buf-map: Add wrapper over memset

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Date:   Thu, 27 Jan 2022 08:28:51 +0100
From:   Christian König <christian.koenig@....com>
To:     Lucas De Marchi <lucas.demarchi@...el.com>,
        intel-gfx@...ts.freedesktop.org
Cc:     dri-devel@...ts.freedesktop.org,
        Matt Roper <matthew.d.roper@...el.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/19] dma-buf-map: Add wrapper over memset

Am 26.01.22 um 21:36 schrieb Lucas De Marchi:
> Just like memcpy_toio(), there is also need to write a direct value to a
> memory block. Add dma_buf_map_memset() to abstract memset() vs memset_io()
>
> Cc: Matt Roper <matthew.d.roper@...el.com>
> Cc: Sumit Semwal <sumit.semwal@...aro.org>
> Cc: Christian König <christian.koenig@....com>
> Cc: linux-media@...r.kernel.org
> Cc: dri-devel@...ts.freedesktop.org
> Cc: linaro-mm-sig@...ts.linaro.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Lucas De Marchi <lucas.demarchi@...el.com>
> ---
>   include/linux/dma-buf-map.h | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
>
> diff --git a/include/linux/dma-buf-map.h b/include/linux/dma-buf-map.h
> index 3514a859f628..c9fb04264cd0 100644
> --- a/include/linux/dma-buf-map.h
> +++ b/include/linux/dma-buf-map.h
> @@ -317,6 +317,23 @@ static inline void dma_buf_map_memcpy_to(struct dma_buf_map *dst, const void *sr
>   		memcpy(dst->vaddr, src, len);
>   }
>   
> +/**
> + * dma_buf_map_memset - Memset into dma-buf mapping
> + * @dst:	The dma-buf mapping structure
> + * @value:	The value to set
> + * @len:	The number of bytes to set in dst
> + *
> + * Set value in dma-buf mapping. Depending on the buffer's location, the helper
> + * picks the correct method of accessing the memory.
> + */
> +static inline void dma_buf_map_memset(struct dma_buf_map *dst, int value, size_t len)
> +{
> +	if (dst->is_iomem)
> +		memset_io(dst->vaddr_iomem, value, len);
> +	else
> +		memset(dst->vaddr, value, len);
> +}
> +

Yeah, that's certainly a valid use case. But maybe directly add a 
dma_buf_map_memset_with_offset() variant as well when that helps to 
avoid patch #2.

Regards,
Christian.

>   /**
>    * dma_buf_map_incr - Increments the address stored in a dma-buf mapping
>    * @map:	The dma-buf mapping structure