Re: [PATCH] power: supply: sbs-battery: Handle unsupported PROP_TIME_TO_EMPTY_NOW

[AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>]

Il 07/03/24 23:05, Nícolas F. R. A. Prado ha scritto:
> Despite the RunTimeToEmpty() (0x11) function being defined in the SBS
> specification as required, it seems that not all batteries implement it.
> On platforms with such batteries, reading the property will cause an
> error to be printed:
> 
> power_supply sbs-8-000b: driver failed to report `time_to_empty_now' property: -5
> 
> This not only pollutes the log, distracting from real problems on the
> device, but also prevents the uevent file from being read since it
> contains all properties, including the faulty one.
> 
> The following table summarizes the findings for a handful of platforms:
> 
> Platform                                Status  Manufacturer    Model
> ------------------------------------------------------------------------
> mt8186-corsola-steelix-sku131072        OK      BYD             L22B3PG0
> mt8195-cherry-tomato-r2                 NOT OK  PANASON         AP16L5J
> mt8192-asurada-spherion-r0              NOT OK  PANASON         AP15O5L
> mt8183-kukui-jacuzzi-juniper-sku16      NOT OK  LGC KT0         AP16L8J
> mt8173-elm-hana                         OK      Sunwoda         L18D3PG1
> sc7180-trogdor-lazor-limozeen-nots-r5   NOT OK  Murata          AP18C4K
> sc7180-trogdor-kingoftown               NOT OK  333-AC-0D-A     GG02047XL
> rk3399-gru-kevin                        OK      SDI             4352D51
> 
> Identify during probe, based on the battery model, if this is one of the
> quirky batteries, and if so, don't register the
> POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW property.
> 
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> ---
>   drivers/power/supply/sbs-battery.c | 45 ++++++++++++++++++++++++++++++++++++++
>   1 file changed, 45 insertions(+)
> 
> diff --git a/drivers/power/supply/sbs-battery.c b/drivers/power/supply/sbs-battery.c
> index a6c204c08232..85ff331cf87a 100644
> --- a/drivers/power/supply/sbs-battery.c
> +++ b/drivers/power/supply/sbs-battery.c
> @@ -1112,6 +1112,49 @@ static const struct power_supply_desc sbs_default_desc = {
>   	.external_power_changed = sbs_external_power_changed,
>   };
>   
> +static const char * const unsupported_time_to_empty_now_models[] = {
> +	"AP16L5J", "AP15O5L", "AP16L8J", "AP18C4K", "GG02047XL"
> +};

I think that you must make sure that this is seen as a quirk, rather than
"something normal" because - as you said - the SBS specification says that
the TIME_TO_EMPTY_NOW is *required*, so, this is a *deviation* from the spec
(so, the SBS implementation in those devices is *out of spec*!).

static const char * const quirk_remove_time_to_empty_now_models
or                        quirk_unsupported_time_to_empty_now_models

...the former, if you want to avoid having a variable name that is 5000 characters
long (:-P); the latter, if you don't care about that (there's no rule anyway).


Besides that, since I didn't like what I just saw, I looked for different
alternatives; the only other one is to de-constify the sbs_properties[] array,
which is something that I also dislike anyway.

I'm not sure if deconstifying that could be acceptable, but if it would, you
would be able to remove-reorder without copies of this and that.

Anyway - the only thing I really want here is to make sure that this is seen
as a quirk and a clear deviation from the specification - everything else is
a plus, and not really a blocker for me.

> +
> +static void sbs_remove_unsupported_properties(struct power_supply_config *psy_cfg,
> +					      struct power_supply_desc *sbs_desc)

P.S.: sbs_quirk_remove_unsupported_properties :-)

Cheers,
Angelo

> +{
> +	enum power_supply_property *new_properties;
> +	struct sbs_info *chip = psy_cfg->drv_data;
> +	bool missing_time_to_empty_now = false;
> +	const char *model_name;
> +	unsigned int new_num_properties;
> +	unsigned int i = 0, j = 0;
> +
> +	model_name = sbs_get_constant_string(chip, POWER_SUPPLY_PROP_MODEL_NAME);
> +	if (IS_ERR(model_name))
> +		return;
> +
> +	for (i = 0; i < ARRAY_SIZE(unsupported_time_to_empty_now_models); i++) {
> +		if (!strcmp(model_name, unsupported_time_to_empty_now_models[i])) {
> +			missing_time_to_empty_now = true;
> +			break;
> +		}
> +	}
> +
> +	if (!missing_time_to_empty_now)
> +		return;
> +
> +	new_num_properties = ARRAY_SIZE(sbs_properties) - 1;
> +	new_properties = devm_kzalloc(&chip->client->dev, new_num_properties * sizeof(sbs_properties[0]), GFP_KERNEL);
> +
> +	for (i = 0; i < sbs_desc->num_properties; i++) {
> +		if (sbs_desc->properties[i] == POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW)
> +			continue;
> +
> +		new_properties[j] = sbs_desc->properties[i];
> +		j++;
> +	}
> +
> +	sbs_desc->properties = new_properties;
> +	sbs_desc->num_properties = new_num_properties;
> +};
> +
>   static int sbs_probe(struct i2c_client *client)
>   {
>   	struct sbs_info *chip;
> @@ -1210,6 +1253,8 @@ static int sbs_probe(struct i2c_client *client)
>   	if (rc)
>   		return rc;
>   
> +	sbs_remove_unsupported_properties(&psy_cfg, sbs_desc);
> +
>   	chip->power_supply = devm_power_supply_register(&client->dev, sbs_desc,
>   						   &psy_cfg);
>   	if (IS_ERR(chip->power_supply))
> 
> ---
> base-commit: 11afac187274a6177a7ac82997f8691c0f469e41
> change-id: 20240307-sbs-time-empty-now-error-322bc074d3f2
> 
> Best regards,