linux-kernel - Re: [PATCH 1/2] firmware: arm_scmi: Fetch and store sensor scale

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Date:   Tue, 7 May 2019 06:31:06 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Florian Fainelli <f.fainelli@...il.com>,
        linux-kernel@...r.kernel.org
Cc:     bcm-kernel-feedback-list@...adcom.com,
        Sudeep Holla <sudeep.holla@....com>,
        Jean Delvare <jdelvare@...e.com>,
        linux-arm-kernel@...ts.infradead.org,
        "open list:HARDWARE MONITORING" <linux-hwmon@...r.kernel.org>
Subject: Re: [PATCH 1/2] firmware: arm_scmi: Fetch and store sensor scale

On 5/6/19 3:41 PM, Florian Fainelli wrote:
> In preparation for dealing with scales within the SCMI HWMON driver,
> fetch and store the sensor unit scale into the scmi_sensor_info
> structure.
> 
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>   drivers/firmware/arm_scmi/sensors.c | 7 ++++++-
>   include/linux/scmi_protocol.h       | 1 +
>   2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/arm_scmi/sensors.c b/drivers/firmware/arm_scmi/sensors.c
> index b53d5cc9c9f6..f324f0a13ebe 100644
> --- a/drivers/firmware/arm_scmi/sensors.c
> +++ b/drivers/firmware/arm_scmi/sensors.c
> @@ -33,7 +33,8 @@ struct scmi_msg_resp_sensor_description {
>   #define NUM_TRIP_POINTS(x)	(((x) >> 4) & 0xff)
>   		__le32 attributes_high;
>   #define SENSOR_TYPE(x)		((x) & 0xff)
> -#define SENSOR_SCALE(x)		(((x) >> 11) & 0x3f)
> +#define SENSOR_SCALE_MASK	0x3f
> +#define SENSOR_SCALE(x)		(((x) >> 11) & SENSOR_SCALE_MASK)
>   #define SENSOR_UPDATE_SCALE(x)	(((x) >> 22) & 0x1f)
>   #define SENSOR_UPDATE_BASE(x)	(((x) >> 27) & 0x1f)
>   		    u8 name[SCMI_MAX_STR_SIZE];
> @@ -140,6 +141,10 @@ static int scmi_sensor_description_get(const struct scmi_handle *handle,
>   			s = &si->sensors[desc_index + cnt];
>   			s->id = le32_to_cpu(buf->desc[cnt].id);
>   			s->type = SENSOR_TYPE(attrh);
> +			s->scale = SENSOR_SCALE(attrh);
> +			/* Sign extend to a full u8 */
> +			if (s->scale & ((SENSOR_SCALE_MASK + 1) >> 1))

The logic here is quite confusing. I think it would be better to define,
say, SENSOR_SCALE_SIGN and use it.

> +				s->scale |= GENMASK(7, 6);
>   			strlcpy(s->name, buf->desc[cnt].name, SCMI_MAX_STR_SIZE);
>   		}
>   
> diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
> index 3105055c00a7..7746f171f108 100644
> --- a/include/linux/scmi_protocol.h
> +++ b/include/linux/scmi_protocol.h
> @@ -144,6 +144,7 @@ struct scmi_power_ops {
>   struct scmi_sensor_info {
>   	u32 id;
>   	u8 type;
> +	u8 scale;

Why not s8 if this is a signed value ?

Thanks,
Guenter

>   	char name[SCMI_MAX_STR_SIZE];
>   };
>   
>