Hi Mita-san,
On Sunday, 22 April 2018 18:56:08 EEST Akinobu Mita wrote:
> The ov772x driver only works when the i2c controller have
> I2C_FUNC_PROTOCOL_MANGLING. However, many i2c controller drivers don't
> support it.
>
> The reason that the ov772x requires I2C_FUNC_PROTOCOL_MANGLING is that
> it doesn't support repeated starts.
>
> This changes the reading ov772x register method so that it doesn't
> require I2C_FUNC_PROTOCOL_MANGLING by calling two separated i2c messages.
As commented in a reply to v1, given that this implementation is in no way
specific to the ov772x driver, I'd prefer implementing the fallback in the I2C
core instead.
> Cc: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
> Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> Cc: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> Cc: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
> Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
> ---
> * v3
> - Remove I2C_CLIENT_SCCB flag set as it isn't needed anymore
>
> drivers/media/i2c/ov772x.c | 20 ++++++++++++++------
> 1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/media/i2c/ov772x.c b/drivers/media/i2c/ov772x.c
> index b62860c..2ae730f 100644
> --- a/drivers/media/i2c/ov772x.c
> +++ b/drivers/media/i2c/ov772x.c
> @@ -542,9 +542,19 @@ static struct ov772x_priv *to_ov772x(struct v4l2_subdev
> *sd) return container_of(sd, struct ov772x_priv, subdev);
> }
>
> -static inline int ov772x_read(struct i2c_client *client, u8 addr)
> +static int ov772x_read(struct i2c_client *client, u8 addr)
> {
> - return i2c_smbus_read_byte_data(client, addr);
> + int ret;
> + u8 val;
> +
> + ret = i2c_master_send(client, &addr, 1);
> + if (ret < 0)
> + return ret;
> + ret = i2c_master_recv(client, &val, 1);
> + if (ret < 0)
> + return ret;
> +
> + return val;
> }
>
> static inline int ov772x_write(struct i2c_client *client, u8 addr, u8
> value) @@ -1255,13 +1265,11 @@ static int ov772x_probe(struct i2c_client
> *client, return -EINVAL;
> }
>
> - if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
> - I2C_FUNC_PROTOCOL_MANGLING)) {
> + if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA)) {
> dev_err(&adapter->dev,
> - "I2C-Adapter doesn't support SMBUS_BYTE_DATA or PROTOCOL_MANGLING
\n");
> + "I2C-Adapter doesn't support SMBUS_BYTE_DATA\n");
> return -EIO;
> }
> - client->flags |= I2C_CLIENT_SCCB;
>
> priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
> if (!priv)
--
Regards,
Laurent Pinchart
