Re: [PATCH v2 2/4] mfd: cros_ec: add EC_PWM function definitions

Doug Anderson
2016-06-16T15:51:50Z

Lee,

On Thu, Jun 16, 2016 at 8:38 AM, Lee Jones <lee.jones@linaro.org> wrote:
> On Thu, 02 Jun 2016, Brian Norris wrote:
>
>> The EC_CMD_PWM_{GET,SET}_DUTY commands allow us to control a PWM that is
>> attached to the EC, rather than the main host SoC. The API provides
>> functionality-based (e.g., keyboard light, backlight) or index-based
>> addressing of the PWM(s). Duty cycles are represented by a 16-bit value,
>> where 0 maps to 0% duty cycle and U16_MAX maps to 100%. The period
>> cannot be controlled.
>>
>> This command set is more generic than, e.g.,
>> EC_CMD_PWM_{GET,SET}_KEYBOARD_BACKLIGHT and could possibly used to
>> replace it on future products.
>>
>> Let's update the command header to include the definitions.
>>
>> Signed-off-by: Brian Norris <briannorris@chromium.org>
>> ---
>> v2: no change
>>
>> include/linux/mfd/cros_ec_commands.h | 31 +++++++++++++++++++++++++++++++
>> 1 file changed, 31 insertions(+)
>>
>> diff --git a/include/linux/mfd/cros_ec_commands.h b/include/linux/mfd/cros_ec_commands.h
>> index 13b630c10d4c..d673575e0ada 100644
>> --- a/include/linux/mfd/cros_ec_commands.h
>> +++ b/include/linux/mfd/cros_ec_commands.h
>> @@ -949,6 +949,37 @@ struct ec_params_pwm_set_fan_duty {
>> uint32_t percent;
>> } __packed;
>>
>> +#define EC_CMD_PWM_SET_DUTY 0x25
>> +/* 16 bit duty cycle, 65535 = 100% */
>> +#define EC_PWM_MAX_DUTY 65535
>
> Any reason this isn't represented in hex, like we do normally?
>
>> +enum ec_pwm_type {
>> + /* All types, indexed by board-specific enum pwm_channel */
>> + EC_PWM_TYPE_GENERIC = 0,
>> + /* Keyboard backlight */
>> + EC_PWM_TYPE_KB_LIGHT,
>> + /* Display backlight */
>> + EC_PWM_TYPE_DISPLAY_LIGHT,
>> + EC_PWM_TYPE_COUNT,
>> +};
>
> Are these comments really necessary? I'd recommend that if your
> defines require comments, then they are not adequately named. In this
> case however, I'd suggest that they are and the comments are
> superfluous.
>
>> +struct ec_params_pwm_set_duty {
>> + uint16_t duty; /* Duty cycle, EC_PWM_MAX_DUTY = 100% */
>> + uint8_t pwm_type; /* ec_pwm_type */
>> + uint8_t index; /* Type-specific index, or 0 if unique */
>> +} __packed;
>
> Please use kerneldoc format.
>
>> +#define EC_CMD_PWM_GET_DUTY 0x26
>> +
>> +struct ec_params_pwm_get_duty {
>> + uint8_t pwm_type; /* ec_pwm_type */
>> + uint8_t index; /* Type-specific index, or 0 if unique */
>> +} __packed;

Probably the reason for all of these non-kernel-isms is that this
isn't a kernel file. From the top of the file:

* NOTE: This file is copied verbatim from the ChromeOS EC Open Source
* project in an attempt to make future updates easy to make.

So the source of truth for this file is
<https://chromium.googlesource.com/chromiumos/platform/ec/+/master/include/ec_commands.h>.

Someone could probably submit a CL to that project to make it a little
more kernel-ish and then we'd have to see if the EC team would accept
such changes...

-Doug