Re: [PATCH 1/4] tc358743: don't use variable length array for I2C writes

["Mats Randgaard (matrandg)" <matrandg@cisco.com>]

On 08/11/2015 05:18 PM, Mauro Carvalho Chehab wrote:
> drivers/media/i2c/tc358743.c:148:19: warning: Variable length array is used.
>
> As the maximum size is 1026, we can't use dynamic var, as it
> would otherwise spend 1056 bytes of the stack at i2c_wr() function.
>
> So, allocate a buffer with the allowed maximum size together with
> the state var.
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
>
> diff --git a/drivers/media/i2c/tc358743.c b/drivers/media/i2c/tc358743.c
> index 2e926317d7e9..fe42c9a1cb78 100644
> --- a/drivers/media/i2c/tc358743.c
> +++ b/drivers/media/i2c/tc358743.c
> @@ -59,6 +59,9 @@ MODULE_LICENSE("GPL");
>   #define EDID_NUM_BLOCKS_MAX 8
>   #define EDID_BLOCK_SIZE 128
>   
> +/* Max transfer size done by I2C transfer functions */
> +#define MAX_XFER_SIZE  (EDID_NUM_BLOCKS_MAX * EDID_BLOCK_SIZE + 2)
> +
>   static const struct v4l2_dv_timings_cap tc358743_timings_cap = {
>   	.type = V4L2_DV_BT_656_1120,
>   	/* keep this initialization for compatibility with GCC < 4.4.6 */
> @@ -94,6 +97,9 @@ struct tc358743_state {
>   	/* edid  */
>   	u8 edid_blocks_written;
>   
> +	/* used by i2c_wr() */
> +	u8 wr_data[MAX_XFER_SIZE];
> +
>   	struct v4l2_dv_timings timings;
>   	u32 mbus_fmt_code;
>   
> @@ -143,9 +149,13 @@ static void i2c_wr(struct v4l2_subdev *sd, u16 reg, u8 *values, u32 n)
>   {
>   	struct tc358743_state *state = to_state(sd);
>   	struct i2c_client *client = state->i2c_client;
> +	u8 *data = state->wr_data;
>   	int err, i;
>   	struct i2c_msg msg;
> -	u8 data[2 + n];
> +
> +	if ((2 + n) > sizeof(state->wr_data))
> +		v4l2_warn(sd, "i2c wr reg=%04x: len=%d is too big!\n",
> +			  reg, 2 + n);
>   
>   	msg.addr = client->addr;
>   	msg.buf = data;

Acked-by: Mats Randgaard <matrandg@cisco.com>