From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from perceval.ideasonboard.com ([213.167.242.64]:50512 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754374AbeDWJSr (ORCPT ); Mon, 23 Apr 2018 05:18:47 -0400 From: Laurent Pinchart Subject: Re: [PATCH v3 02/11] media: ov772x: allow i2c controllers without I2C_FUNC_PROTOCOL_MANGLING Date: Mon, 23 Apr 2018 12:18:58 +0300 Message-ID: <4036479.nT1QDtF4Ij@avalon> In-Reply-To: <1524412577-14419-3-git-send-email-akinobu.mita@gmail.com> References: <1524412577-14419-1-git-send-email-akinobu.mita@gmail.com> <1524412577-14419-3-git-send-email-akinobu.mita@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: devicetree-owner@vger.kernel.org To: Akinobu Mita Cc: linux-media@vger.kernel.org, devicetree@vger.kernel.org, Jacopo Mondi , Hans Verkuil , Sakari Ailus , Mauro Carvalho Chehab List-ID: 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 > Cc: Laurent Pinchart > Cc: Hans Verkuil > Cc: Sakari Ailus > Cc: Mauro Carvalho Chehab > Signed-off-by: Akinobu Mita > --- > * 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