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

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Date:   Sat, 25 Apr 2020 16:29:40 +0200
From:   Oscar Carter <oscar.carter@....com>
To:     Joe Perches <joe@...ches.com>
Cc:     Oscar Carter <oscar.carter@....com>,
        Forest Bond <forest@...ttletooquiet.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        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, Apr 25, 2020 at 05:50:39AM -0700, Joe Perches wrote:
> 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.
>

Great. I will add all this information to clarify the commit changelog.

>
> > 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
> >
>
thanks,
oscar carter