linux-kernel - Re: [PATCH 1/3] staging: vt6656: Remove the local variable "array"

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Message-ID: <b5aa72347748f35245f2fd0272ab3957179ed2eb.camel@perches.com>
Date:   Sat, 25 Apr 2020 05:50:39 -0700
From:   Joe Perches <joe@...ches.com>
To:     Oscar Carter <oscar.carter@....com>,
        Forest Bond <forest@...ttletooquiet.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Malcolm Priestley <tvboxspy@...il.com>,
        Quentin Deslandes <quentin.deslandes@...ev.co.uk>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] staging: vt6656: Remove the local variable "array"

On Sat, 2020-04-25 at 14:38 +0200, Oscar Carter wrote:
> Remove the local variable "array" and all the memcpy function calls
> because this copy operation from different arrays to this variable is
> unnecessary.

You might write here that vnt_control_out already does
a kmemdup copy of its const char *buffer argument and
this was made unnecessary by:

commit 12ecd24ef93277e4e5feaf27b0b18f2d3828bc5e
Author: Malcolm Priestley <tvboxspy@...il.com>
Date:   Sat Apr 22 11:14:57 2017 +0100

    staging: vt6656: use off stack for out buffer USB transfers.
    
    Since 4.9 mandated USB buffers be heap allocated this causes the driver
    to fail.
    
    Since there is a wide range of buffer sizes use kmemdup to create
    allocated buffer.
 

> The same result can be achieved using the arrays directly.
> 
> Signed-off-by: Oscar Carter <oscar.carter@....com>
> ---
>  drivers/staging/vt6656/rf.c | 21 +++++----------------
>  1 file changed, 5 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/staging/vt6656/rf.c b/drivers/staging/vt6656/rf.c
> index 06fa8867cfa3..82d3b6081b5b 100644
> --- a/drivers/staging/vt6656/rf.c
> +++ b/drivers/staging/vt6656/rf.c
> @@ -770,7 +770,6 @@ int vnt_rf_table_download(struct vnt_private *priv)
>  	u16 length1 = 0, length2 = 0, length3 = 0;
>  	u8 *addr1 = NULL, *addr2 = NULL, *addr3 = NULL;
>  	u16 length, value;
> -	u8 array[256];
> 
>  	switch (priv->rf_type) {
>  	case RF_AL2230:
> @@ -817,10 +816,8 @@ int vnt_rf_table_download(struct vnt_private *priv)
>  	}
> 
>  	/* Init Table */
> -	memcpy(array, addr1, length1);
> -
>  	ret = vnt_control_out(priv, MESSAGE_TYPE_WRITE, 0,
> -			      MESSAGE_REQUEST_RF_INIT, length1, array);
> +			      MESSAGE_REQUEST_RF_INIT, length1, addr1);
>  	if (ret)
>  		goto end;
> 
> @@ -832,10 +829,8 @@ int vnt_rf_table_download(struct vnt_private *priv)
>  		else
>  			length = length2;
> 
> -		memcpy(array, addr2, length);
> -
>  		ret = vnt_control_out(priv, MESSAGE_TYPE_WRITE, value,
> -				      MESSAGE_REQUEST_RF_CH0, length, array);
> +				      MESSAGE_REQUEST_RF_CH0, length, addr2);
>  		if (ret)
>  			goto end;
> 
> @@ -852,10 +847,8 @@ int vnt_rf_table_download(struct vnt_private *priv)
>  		else
>  			length = length3;
> 
> -		memcpy(array, addr3, length);
> -
>  		ret = vnt_control_out(priv, MESSAGE_TYPE_WRITE, value,
> -				      MESSAGE_REQUEST_RF_CH1, length, array);
> +				      MESSAGE_REQUEST_RF_CH1, length, addr3);
>  		if (ret)
>  			goto end;
> 
> @@ -870,11 +863,9 @@ int vnt_rf_table_download(struct vnt_private *priv)
>  		addr1 = &al7230_init_table_amode[0][0];
>  		addr2 = &al7230_channel_table2[0][0];
> 
> -		memcpy(array, addr1, length1);
> -
>  		/* Init Table 2 */
>  		ret = vnt_control_out(priv, MESSAGE_TYPE_WRITE, 0,
> -				      MESSAGE_REQUEST_RF_INIT2, length1, array);
> +				      MESSAGE_REQUEST_RF_INIT2, length1, addr1);
>  		if (ret)
>  			goto end;
> 
> @@ -886,11 +877,9 @@ int vnt_rf_table_download(struct vnt_private *priv)
>  			else
>  				length = length2;
> 
> -			memcpy(array, addr2, length);
> -
>  			ret = vnt_control_out(priv, MESSAGE_TYPE_WRITE, value,
>  					      MESSAGE_REQUEST_RF_CH2, length,
> -					      array);
> +					      addr2);
>  			if (ret)
>  				goto end;
> 
> --
> 2.20.1
>