RE: [PATCH v2] media: ov8856: Add support for OV8856 sensor

["Yeh, Andy" <andy.yeh@intel.com>]

Hi Ben,

You are referring to older type of sensor i2c control. You can refer to IMX258 driver.  
drivers/media/i2c/imx258.c

/* Write registers up to 2 at a time */
static int imx258_write_reg(struct imx258 *imx258, u16 reg, u32 len, u32 val)
{
        struct i2c_client *client = v4l2_get_subdevdata(&imx258->sd);
        u8 buf[6];

        if (len > 4)
                return -EINVAL;

        put_unaligned_be16(reg, buf);
        put_unaligned_be32(val << (8 * (4 - len)), buf + 2);
        if (i2c_master_send(client, buf, len + 2) != len + 2)
                return -EIO;

        return 0;
}

Regards, Andy

>-----Original Message-----
>From: Tomasz Figa [mailto:tfiga@chromium.org]
>Sent: Tuesday, January 15, 2019 11:23 AM
>To: Kao, Ben <ben.kao@intel.com>
>Cc: Linux Media Mailing List <linux-media@vger.kernel.org>; Sakari Ailus
><sakari.ailus@linux.intel.com>; Yeh, Andy <andy.yeh@intel.com>
>Subject: Re: [PATCH v2] media: ov8856: Add support for OV8856 sensor
>
>Hi Ben,
>
>On Fri, Jan 11, 2019 at 12:12 PM Ben Kao <ben.kao@intel.com> wrote:
>>
>> This patch adds driver for Omnivision's ov8856 sensor, the driver
>> supports following features:
>[snip]
>> +static int ov8856_write_reg(struct ov8856 *ov8856, u16 reg, u16 len,
>> +u32 __val) {
>> +       struct i2c_client *client = v4l2_get_subdevdata(&ov8856->sd);
>> +       unsigned int buf_i, val_i;
>> +       u8 buf[6];
>> +       u8 *val_p;
>> +       __be32 val;
>> +
>> +       if (len > 4)
>> +               return -EINVAL;
>> +
>> +       buf[0] = reg >> 8;
>> +       buf[1] = reg & 0xff;
>
>The two lines above can be simplified into one put_unaligned_be16(reg, buf);
>
>> +
>> +       val = cpu_to_be32(__val);
>> +       val_p = (u8 *)&val;
>> +       buf_i = 2;
>> +       val_i = 4 - len;
>> +
>> +       while (val_i < 4)
>> +               buf[buf_i++] = val_p[val_i++];
>
>All the code above can be simplified into:
>
>val <<= 8 * (4 - len);
>put_unaligned_be32(val, buf + 2);
>
>> +
>> +       if (i2c_master_send(client, buf, len + 2) != len + 2)
>> +               return -EIO;
>> +
>> +       return 0;
>> +}
>
>Best regards,
>Tomasz