linux-kernel - Re: [PATCH 6/7] mfd / platform: cros_ec: instantiate only if th EC has a VBC NVRAM.

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Date:   Thu, 22 Nov 2018 11:14:01 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     lee.jones@...aro.org, gwendal@...omium.org, drinkcat@...omium.org,
        linux-kernel@...r.kernel.org, groeck@...omium.org,
        kernel@...labora.com, bleung@...omium.org,
        Olof Johansson <olof@...om.net>
Subject: Re: [PATCH 6/7] mfd / platform: cros_ec: instantiate only if th EC
 has a VBC NVRAM.

On Thu, Nov 22, 2018 at 12:33:55PM +0100, Enric Balletbo i Serra wrote:
> The cros-ec-vbc driver is DT-only and there is a DT property that
> indicates if the EC has the VCB NVRAM, in such case instantiate the
> driver but don't instantiate on the other cases.
> 
> To do this move the check code to its parent instead of play with the
> attribute group visibility. This changes a bit the actual behaviour.
> Before the patch if an EC doesn't have a VBC NVRAM an empty vbc folder
> is created in /sys/class/chromeos/<ec device>, after the patch the empty
> folder is not created, so, the folder is only created if the vbc is set.
> 
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> ---
> 
>  drivers/mfd/cros_ec_dev.c             | 24 +++++++++++++++++++++++-
>  drivers/platform/chrome/cros_ec_vbc.c | 16 ----------------
>  2 files changed, 23 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
> index fc235af6da65..a63588953760 100644
> --- a/drivers/mfd/cros_ec_dev.c
> +++ b/drivers/mfd/cros_ec_dev.c
> @@ -21,6 +21,7 @@
>  #include <linux/mfd/core.h>
>  #include <linux/module.h>
>  #include <linux/mod_devicetable.h>
> +#include <linux/of_platform.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm.h>
>  #include <linux/slab.h>
> @@ -400,7 +401,10 @@ static const struct mfd_cell cros_ec_platform_cells[] = {
>  	{ .name = "cros-ec-debugfs" },
>  	{ .name = "cros-ec-lightbar" },
>  	{ .name = "cros-ec-sysfs" },
> -	{ .name = "cros-ec-vbc" },
> +};
> +
> +static const struct mfd_cell cros_ec_vbc_cells[] = {
> +	{ .name = "cros-ec-vbc" }
>  };
>  
>  static int ec_device_probe(struct platform_device *pdev)
> @@ -409,6 +413,7 @@ 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 = devm_kzalloc(dev, sizeof(*ec), GFP_KERNEL);
> +	struct device_node *node;
>  
>  	if (!ec)
>  		return retval;
> @@ -492,6 +497,23 @@ static int ec_device_probe(struct platform_device *pdev)
>  		dev_err(ec->dev,
>  			"failed to add cros-ec platform devices: %d\n", retval);
>  
> +	/* Check whether this EC instance has a VBC NVRAM */
> +	node = ec->ec_dev->dev->of_node;
> +	if (IS_ENABLED(CONFIG_OF) && node) {

Is IS_ENABLED() necessary here ? Seems to me node should always be NULL
in this case.

> +		if (of_property_read_bool(node, "google,has-vbc-nvram")) {
> +			dev_err(dev, "device VBC found.\n");

dev_err ?

> +			retval = devm_mfd_add_devices(ec->dev,
> +					PLATFORM_DEVID_AUTO,
> +					cros_ec_vbc_cells,
> +					ARRAY_SIZE(cros_ec_vbc_cells),
> +					NULL, 0, NULL);
> +			if (retval)
> +				dev_err(ec->dev,
> +					"failed to add VBC devices: %d\n",
> +					retval);

Since the error is ignored, maybe better dev_warn() ?

> +		}
> +	}
> +
>  	return 0;
>  
>  failed:
> diff --git a/drivers/platform/chrome/cros_ec_vbc.c b/drivers/platform/chrome/cros_ec_vbc.c
> index 374153e3dc13..b7b81fe0fb25 100644
> --- a/drivers/platform/chrome/cros_ec_vbc.c
> +++ b/drivers/platform/chrome/cros_ec_vbc.c
> @@ -108,21 +108,6 @@ static ssize_t vboot_context_write(struct file *filp, struct kobject *kobj,
>  	return data_sz;
>  }
>  
> -static umode_t cros_ec_vbc_is_visible(struct kobject *kobj,
> -				      struct bin_attribute *a, int n)
> -{
> -	struct device *dev = container_of(kobj, struct device, kobj);
> -	struct cros_ec_dev *ec = to_cros_ec_dev(dev);
> -	struct device_node *np = ec->ec_dev->dev->of_node;
> -
> -	if (IS_ENABLED(CONFIG_OF) && np) {
> -		if (of_property_read_bool(np, "google,has-vbc-nvram"))
> -			return a->attr.mode;
> -	}
> -
> -	return 0;
> -}
> -
>  static BIN_ATTR_RW(vboot_context, 16);
>  
>  static struct bin_attribute *cros_ec_vbc_bin_attrs[] = {
> @@ -133,7 +118,6 @@ static struct bin_attribute *cros_ec_vbc_bin_attrs[] = {
>  struct attribute_group cros_ec_vbc_attr_group = {
>  	.name = "vbc",
>  	.bin_attrs = cros_ec_vbc_bin_attrs,
> -	.is_bin_visible = cros_ec_vbc_is_visible,
>  };
>  
>  static int cros_ec_vbc_probe(struct platform_device *pd)