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SubjectRe: [PATCH v7 2/2] media:imx274 V4l2 driver for Sony imx274 CMOS sensor
Hi Leon,

One more question below.

On Mon, Oct 02, 2017 at 01:26:49PM -0700, Leon Luo wrote:
...
> +/*
> + * imx274_set_frame_interval - Function called when setting frame interval
> + * @priv: Pointer to device structure
> + * @frame_interval: Variable for frame interval
> + *
> + * Change frame interval by updating VMAX value
> + * The caller should hold the mutex lock imx274->lock if necessary
> + *
> + * Return: 0 on success
> + */
> +static int imx274_set_frame_interval(struct stimx274 *priv,
> + struct v4l2_fract frame_interval)
> +{
> + int err;
> + u32 frame_length, req_frame_rate;
> + u16 svr;
> + u16 hmax;
> + u8 reg_val[2];
> +
> + dev_dbg(&priv->client->dev, "%s: input frame interval = %d / %d",
> + __func__, frame_interval.numerator,
> + frame_interval.denominator);
> +
> + if (frame_interval.denominator == 0) {

Shouldn't this be numerator? If numerator is 0, then there will be division
by zero below.

> + err = -EINVAL;
> + goto fail;
> + }
> +
> + req_frame_rate = (u32)(frame_interval.denominator
> + / frame_interval.numerator);
> +
> + /* boundary check */
> + if (req_frame_rate > max_frame_rate[priv->mode_index]) {
> + frame_interval.numerator = 1;
> + frame_interval.denominator =
> + max_frame_rate[priv->mode_index];
> + } else if (req_frame_rate < IMX274_MIN_FRAME_RATE) {
> + frame_interval.numerator = 1;
> + frame_interval.denominator = IMX274_MIN_FRAME_RATE;
> + }
> +
> + /*
> + * VMAX = 1/frame_rate x 72M / (SVR+1) / HMAX
> + * frame_length (i.e. VMAX) = (frame_interval) x 72M /(SVR+1) / HMAX
> + */
> +
> + /* SVR */
> + err = imx274_read_reg(priv, IMX274_SVR_REG_LSB, &reg_val[0]);
> + if (err)
> + goto fail;
> + err = imx274_read_reg(priv, IMX274_SVR_REG_MSB, &reg_val[1]);
> + if (err)
> + goto fail;
> + svr = (reg_val[1] << IMX274_SHIFT_8_BITS) + reg_val[0];
> + dev_dbg(&priv->client->dev,
> + "%s : register SVR = %d\n", __func__, svr);
> +
> + /* HMAX */
> + err = imx274_read_reg(priv, IMX274_HMAX_REG_LSB, &reg_val[0]);
> + if (err)
> + goto fail;
> + err = imx274_read_reg(priv, IMX274_HMAX_REG_MSB, &reg_val[1]);
> + if (err)
> + goto fail;
> + hmax = (reg_val[1] << IMX274_SHIFT_8_BITS) + reg_val[0];
> + dev_dbg(&priv->client->dev,
> + "%s : register HMAX = %d\n", __func__, hmax);
> +
> + frame_length = IMX274_PIXCLK_CONST1 / (svr + 1) / hmax
> + * frame_interval.numerator
> + / frame_interval.denominator;
> +
> + err = imx274_set_frame_length(priv, frame_length);
> + if (err)
> + goto fail;
> +
> + priv->frame_interval = frame_interval;
> + return 0;
> +
> +fail:
> + dev_err(&priv->client->dev, "%s error = %d\n", __func__, err);
> + return err;
> +}

--
Regards,

Sakari Ailus
e-mail: sakari.ailus@iki.fi

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