linux-kernel - Re: [PATCH linux v7 3/6] hwmon: occ: Add I2C transport implementation for SCOM operations

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Message-ID: <CACPK8XcdsG83HsQW1Pv5zR339mgTzYjfuLQE+gE8yk8Z88MrTA@mail.gmail.com>
Date:   Fri, 10 Feb 2017 16:01:28 +1030
From:   Joel Stanley <joel@....id.au>
To:     eajames <eajames@...ux.vnet.ibm.com>
Cc:     Guenter Roeck <linux@...ck-us.net>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        linux-doc@...r.kernel.org, jdelvare@...e.com, corbet@....net,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Andrew Jeffery <andrew@...id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        "Edward A. James" <eajames@...ibm.com>
Subject: Re: [PATCH linux v7 3/6] hwmon: occ: Add I2C transport implementation
 for SCOM operations

On Wed, Feb 8, 2017 at 9:40 AM,  <eajames@...ux.vnet.ibm.com> wrote:
> From: "Edward A. James" <eajames@...ibm.com>
>
> Add functions to send SCOM operations over I2C bus. The BMC can
> communicate with the Power8 host processor over I2C, but needs to use SCOM
> operations in order to access the OCC register space.

This doesn't need to be separate from the p8_occ_i2c.c file. You can
remove a layer of function calls by merging this in and having these
be your getscom putscom bus_ops callbacks.

> Signed-off-by: Edward A. James <eajames@...ibm.com>
> Signed-off-by: Andrew Jeffery <andrew@...id.au>
> ---
>  drivers/hwmon/occ/occ_scom_i2c.c | 77 ++++++++++++++++++++++++++++++++++++++++
>  drivers/hwmon/occ/occ_scom_i2c.h | 26 ++++++++++++++
>  2 files changed, 103 insertions(+)
>  create mode 100644 drivers/hwmon/occ/occ_scom_i2c.c
>  create mode 100644 drivers/hwmon/occ/occ_scom_i2c.h
>
> diff --git a/drivers/hwmon/occ/occ_scom_i2c.c b/drivers/hwmon/occ/occ_scom_i2c.c
> new file mode 100644
> index 0000000..74bd6ff
> --- /dev/null
> +++ b/drivers/hwmon/occ/occ_scom_i2c.c
> @@ -0,0 +1,77 @@

> +
> +int occ_i2c_getscom(void *bus, u32 address, u64 *data)
> +{
> +       ssize_t rc;
> +       u64 buf;

If you add endianness annotations sparse can check your types are
consistent. The warning looks like this:

make C=2 drivers/hwmon/occ/occ_scom_i2c.o
drivers/hwmon/occ/occ_scom_i2c.c:48:17: warning: cast to restricted __be64

Which tells you it expects the type you pass to be64_to_cpu to be __be64.


> +       struct i2c_client *client = bus;
> +       struct i2c_msg msgs[2];
> +
> +       msgs[0].addr = client->addr;
> +       msgs[0].flags = client->flags & I2C_M_TEN;
> +       msgs[0].len = sizeof(u32);
> +       msgs[0].buf = (char *)&address;
> +
> +       msgs[1].addr = client->addr;
> +       msgs[1].flags = client->flags & I2C_M_TEN;
> +       msgs[1].flags |= I2C_M_RD;

I first thought you had made a mistake here. Instead you could do:

       msgs[1].flags = client->flags & I2C_M_TEN | I2C_M_RD;

> +       msgs[1].len = sizeof(u64);
> +       msgs[1].buf = (char *)&buf;
> +
> +       rc = i2c_transfer(client->adapter, msgs, 2);
> +       if (rc < 0)
> +               return rc;
> +