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Message-ID: <f5a23931-6c05-4eed-91a5-5b829ad3aa94@embeddedor.com>
Date: Wed, 13 Dec 2023 14:14:53 -0600
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Subject: Re: [PATCH 1/6] wifi: ath10k: use flexible array in struct
 wmi_host_mem_chunks
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To: Jeff Johnson <quic_jjohnson@quicinc.com>, Kalle Valo <kvalo@kernel.org>
Cc: Kees Cook <keescook@chromium.org>, ath10k@lists.infradead.org,
 linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20231213-wmi_host_mem_chunks_flexarray-v1-0-92922d92fa2c@quicinc.com>
 <20231213-wmi_host_mem_chunks_flexarray-v1-1-92922d92fa2c@quicinc.com>
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
In-Reply-To: <20231213-wmi_host_mem_chunks_flexarray-v1-1-92922d92fa2c@quicinc.com>
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On 12/13/23 11:06, Jeff Johnson wrote:
> Currently struct wmi_host_mem_chunks defines:
> 	struct host_memory_chunk items[1];
> 
> Per the guidance in [1] this should be a flexible array. However there
> is a documented requirement:
> 	some fw revisions require at least 1 chunk regardless of count
> 
> To satisfy this requirement, follow the guidance from [2] and wrap the
> array in a union which contains both the flexible array and a single
> instance of the underlying struct. Since the footprint of the struct
> is unchanged, no additional driver changes are required.
> 
> No functional changes, compile tested only.
> 
> [1] https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays
> [2] https://lore.kernel.org/linux-wireless/202308301529.AC90A9EF98@keescook/
> 
> Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks!
--
Gustavo

> ---
>   drivers/net/wireless/ath/ath10k/wmi.h | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/ath/ath10k/wmi.h b/drivers/net/wireless/ath/ath10k/wmi.h
> index 9146df98fcee..833ce0251a2c 100644
> --- a/drivers/net/wireless/ath/ath10k/wmi.h
> +++ b/drivers/net/wireless/ath/ath10k/wmi.h
> @@ -3069,7 +3069,10 @@ struct host_memory_chunk {
>   struct wmi_host_mem_chunks {
>   	__le32 count;
>   	/* some fw revisions require at least 1 chunk regardless of count */
> -	struct host_memory_chunk items[1];
> +	union {
> +		struct host_memory_chunk item;
> +		DECLARE_FLEX_ARRAY(struct host_memory_chunk, items);
> +	};
>   } __packed;
>   
>   struct wmi_init_cmd {
>