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SubjectRe: [PATCH v5 3/4] pmbus (core): Add virtual page config bit
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On 11/17/2017 07:26 PM, Andrew Jeffery wrote:
> Some circumstances call for virtual pages, to expose multiple values
> packed into an extended PMBus register in a manner non-compliant with
> the PMBus standard. An example of this is the Maxim MAX31785 controller, which
> extends the READ_FAN_SPEED_1 PMBus register from two to four bytes to support
> tach readings for both rotors of a dual rotor fan. This extended register
> contains two word-sized values, one reporting the rate of the fastest rotor,
> the other the rate of the slowest. The concept of virtual pages aids this
> situation by mapping the page number onto the value to be selected from the
> vectored result.
>
> We should not try to set virtual pages on the device as such a page explicitly
> doesn't exist; add a flag so we can avoid doing so.
>
> Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
> ---
> drivers/hwmon/pmbus/pmbus.h | 2 ++
> drivers/hwmon/pmbus/pmbus_core.c | 10 +++++++---
> 2 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
> index b54d7604d3ef..d39d506aa63e 100644
> --- a/drivers/hwmon/pmbus/pmbus.h
> +++ b/drivers/hwmon/pmbus/pmbus.h
> @@ -372,6 +372,8 @@ enum pmbus_sensor_classes {
> #define PMBUS_HAVE_PWM12 BIT(20)
> #define PMBUS_HAVE_PWM34 BIT(21)
>
> +#define PMBUS_PAGE_VIRTUAL BIT(31)
> +
> enum pmbus_data_format { linear = 0, direct, vid };
> enum vrm_version { vr11 = 0, vr12, vr13 };
>
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index 631db88526b6..ba97230fcde7 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -164,14 +164,18 @@ int pmbus_set_page(struct i2c_client *client, int page)
> int rv = 0;
> int newpage;
>
> - if (page >= 0 && page != data->currpage) {
> + if (page < 0 || page == data->currpage)
> + return 0;
> +
> + if (!(data->info->func[page] & PMBUS_PAGE_VIRTUAL)) {
> rv = i2c_smbus_write_byte_data(client, PMBUS_PAGE, page);
> newpage = i2c_smbus_read_byte_data(client, PMBUS_PAGE);
> if (newpage != page)
> rv = -EIO;

This should probably be something like
rv = i2c_smbus_write_byte_data(client, PMBUS_PAGE, page);
if (rv < 0)
return rv;
newpage = i2c_smbus_read_byte_data(client, PMBUS_PAGE);
if (newpage < 0)
return newpage;
if (newpage != page)
return -EIO;

We can actually drop 'newpage' and just use 'rv'.

> - else
> - data->currpage = page;
> }
> +
> + data->currpage = page;
> +

... otherwise currpage is set even on error.

> return rv;

this can then be
return 0;

> }
> EXPORT_SYMBOL_GPL(pmbus_set_page);
>

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