2018-04-09 15:58 GMT+09:00 jacopo mondi <jacopo@xxxxxxxxxx>:
> Hello Akinobu,
> thank you for the patch.
>
> On which platform have you tested the series (just curious) ?
I use Zynq-7000 development board with Xilinx Video IP driver and
custom video pipeline design based on the example reference project.
> On Sun, Apr 08, 2018 at 12:48:05AM +0900, 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 change adds an alternative method for reading from ov772x register
>> which uses two separated i2c messages for the i2c controllers without
>> I2C_FUNC_PROTOCOL_MANGLING.
>
> Actually, and please correct me if I'm wrong, what I see here is that
> an i2c_master_send+i2c_master_recv sequence is equivalent to a mangled
> smbus transaction:
>
> i2c_smbus_read_byte_data | I2C_CLIENT_SCCB:
> S Addr Wr [A] Comm [A] P S Addr Rd [A] [Data] NA P
>
> i2c_master_send() + i2c_master_recv():
> S Addr Wr [A] Data [A] P
> S Addr Rd [A] [Data] NA P
>
> I wonder if it is not worth to ditch the existing read() function in
> favour of your new proposed one completely.
>
> I have tested it on the Migo-R board where I have an ov772x installed
> and it works fine.
I'll replace the read() function to the new implementation in the next
version of this patchset. Although handling in the I2C core is fascinating,
I feel the area of influence is a bit large.
> Although I would like to have a confirmation this is fine by people
> how has seen more i2c adapters in action than me :)
>
> Thanks
> j
>
>>
>> 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>
>> ---
>> drivers/media/i2c/ov772x.c | 42 +++++++++++++++++++++++++++++++++---------
>> 1 file changed, 33 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/media/i2c/ov772x.c b/drivers/media/i2c/ov772x.c
>> index b62860c..283ae2c 100644
>> --- a/drivers/media/i2c/ov772x.c
>> +++ b/drivers/media/i2c/ov772x.c
>> @@ -424,6 +424,7 @@ struct ov772x_priv {
>> /* band_filter = COM8[5] ? 256 - BDBASE : 0 */
>> unsigned short band_filter;
>> unsigned int fps;
>> + int (*reg_read)(struct i2c_client *client, u8 addr);
>> };
>>
>> /*
>> @@ -542,11 +543,34 @@ 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)
>> +{
>> + struct v4l2_subdev *sd = i2c_get_clientdata(client);
>> + struct ov772x_priv *priv = to_ov772x(sd);
>> +
>> + return priv->reg_read(client, addr);
>> +}
>> +
>> +static int ov772x_reg_read(struct i2c_client *client, u8 addr)
>> {
>> return i2c_smbus_read_byte_data(client, addr);
>> }
>>
>> +static int ov772x_reg_read_fallback(struct i2c_client *client, u8 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)
>> {
>> return i2c_smbus_write_byte_data(client, addr, value);
>> @@ -1255,20 +1279,20 @@ static int ov772x_probe(struct i2c_client *client,
>> return -EINVAL;
>> }
>>
>> - if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
>> - I2C_FUNC_PROTOCOL_MANGLING)) {
>> - dev_err(&adapter->dev,
>> - "I2C-Adapter doesn't support SMBUS_BYTE_DATA or PROTOCOL_MANGLING\n");
>> - return -EIO;
>> - }
>> - client->flags |= I2C_CLIENT_SCCB;
>> -
>> priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
>> if (!priv)
>> return -ENOMEM;
>>
>> priv->info = client->dev.platform_data;
>>
>> + if (i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
>> + I2C_FUNC_PROTOCOL_MANGLING))
>> + priv->reg_read = ov772x_reg_read;
>> + else
>> + priv->reg_read = ov772x_reg_read_fallback;
>> +
>> + client->flags |= I2C_CLIENT_SCCB;
>> +
>> v4l2_i2c_subdev_init(&priv->subdev, client, &ov772x_subdev_ops);
>> v4l2_ctrl_handler_init(&priv->hdl, 3);
>> v4l2_ctrl_new_std(&priv->hdl, &ov772x_ctrl_ops,
>> --
>> 2.7.4
>>
