2018-04-23 18:18 GMT+09:00 Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>:
> 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.
Do you have any ideas how to implement in the I2C core?
I wonder if I can modify i2c_smbus_read_byte_data() or i2c_transfer()
for I2C_CLIENT_SCCB.
>> 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
>
>
>
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