linux-kernel - Re: [PATCH v2] mfd: cros_ec_dev: Only register PCHG device if present

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Date:   Tue, 19 Apr 2022 00:22:19 +0000
From:   Prashant Malani <pmalani@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Lee Jones <lee.jones@...aro.org>, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev, Tzung-Bi Shih <tzungbi@...nel.org>,
        Daisuke Nojiri <dnojiri@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        chrome-platform@...ts.linux.dev
Subject: Re: [PATCH v2] mfd: cros_ec_dev: Only register PCHG device if present

Hey Stephen,

On Apr 18 17:04, Stephen Boyd wrote:
> Don't create a device for the peripheral charger (PCHG) if there aren't
> any peripheral charger ports. This removes a device on most ChromeOS
> systems, because the peripheral charger functionality isn't always
> present.
> 
> Cc: Prashant Malani <pmalani@...omium.org>
> Cc: Tzung-Bi Shih <tzungbi@...nel.org>
> Cc: Daisuke Nojiri <dnojiri@...omium.org>
> Cc: Benson Leung <bleung@...omium.org>
> Cc: Guenter Roeck <groeck@...omium.org>
> Cc: <chrome-platform@...ts.linux.dev>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
FWIW:
Reviewed-by: Prashant Malani <pmalani@...omium.org>

> ---
> 
> Changes from v1 (https://lore.kernel.org/r/20220415003253.1973106-1-swboyd@chromium.org):
>  * Use cros_ec_command()
>  * Drop the other patches that aren't needed anymore
> 
>  drivers/mfd/cros_ec_dev.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
> index 546feef851ab..596731caf407 100644
> --- a/drivers/mfd/cros_ec_dev.c
> +++ b/drivers/mfd/cros_ec_dev.c
> @@ -114,6 +114,9 @@ static const struct mfd_cell cros_ec_platform_cells[] = {
>  	{ .name = "cros-ec-chardev", },
>  	{ .name = "cros-ec-debugfs", },
>  	{ .name = "cros-ec-sysfs", },
> +};
> +
> +static const struct mfd_cell cros_ec_pchg_cells[] = {
>  	{ .name = "cros-ec-pchg", },
>  };
>  
> @@ -137,6 +140,7 @@ static int ec_device_probe(struct platform_device *pdev)
>  	struct device *dev = &pdev->dev;
>  	struct cros_ec_platform *ec_platform = dev_get_platdata(dev);
>  	struct cros_ec_dev *ec = kzalloc(sizeof(*ec), GFP_KERNEL);
> +	struct ec_response_pchg_count pchg_count;
>  	int i;
>  
>  	if (!ec)
> @@ -242,6 +246,21 @@ static int ec_device_probe(struct platform_device *pdev)
>  		}
>  	}
>  
> +	/*
> +	 * The PCHG device cannot be detected by sending EC_FEATURE_GET_CMD, but
> +	 * it can be detected by querying the number of peripheral chargers.
> +	 */
> +	retval = cros_ec_command(ec->ec_dev, 0, EC_CMD_PCHG_COUNT, NULL, 0,
> +				 &pchg_count, sizeof(pchg_count));
> +	if (retval >= 0 && pchg_count.port_count) {
> +		retval = mfd_add_hotplug_devices(ec->dev,
> +					cros_ec_pchg_cells,
> +					ARRAY_SIZE(cros_ec_pchg_cells));
> +		if (retval)
> +			dev_warn(ec->dev, "failed to add pchg: %d\n",
> +				 retval);
Tiny nit: Can this fit in 1 line (100 chars[1])?


BR,

-Prashant

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bdc48fa11e46f867ea4d75fa59ee87a7f48be144