linux-kernel - Re: [PATCH v3 6/8] mfd / platform: cros_ec: instantiate only if th EC has a VBC NVRAM.

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Date:   Mon, 10 Dec 2018 10:30:49 -0800
From:   Guenter Roeck <groeck@...gle.com>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Gwendal Grignou <gwendal@...omium.org>,
        Nicolas Boichat <drinkcat@...omium.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Guenter Roeck <groeck@...omium.org>, kernel@...labora.com,
        Benson Leung <bleung@...omium.org>,
        Olof Johansson <olof@...om.net>
Subject: Re: [PATCH v3 6/8] mfd / platform: cros_ec: instantiate only if th EC
 has a VBC NVRAM.

On Mon, Dec 10, 2018 at 10:15 AM Guenter Roeck <groeck@...gle.com> wrote:
>
> On Tue, Nov 27, 2018 at 4:19 AM Enric Balletbo i Serra
> <enric.balletbo@...labora.com> 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>
>
> Reviewed-by: Guenter Roeck <groeck@...omium.org>
>
Forgot to mention: It would be nice if the subject would mention what
is only instantiated if there is a VBC NVRAM, and there is a typo (th
instead of the).

Guenter

> > ---
> >
> > Changes in v3:
> > - Fixed build error as reported by kbuild test robot.
> >
> > Changes in v2:
> > - Remove unnecessary IS_ENABLED.
> > - Remove dev_err message telling that VBC is found.
> > - Use dev_warn instead of dev_err as the error is ignored.
> >
> >  drivers/mfd/cros_ec_dev.c             | 19 ++++++++++++++++++-
> >  drivers/platform/chrome/cros_ec_vbc.c | 16 ----------------
> >  2 files changed, 18 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
> > index d9b16ce79319..1ba98a32715e 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>
> > @@ -386,12 +387,16 @@ 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)
> >  {
> >         int retval = -ENOMEM;
> > +       struct device_node *node;
> >         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);
> > @@ -479,6 +484,18 @@ static int ec_device_probe(struct platform_device *pdev)
> >                          "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 (of_property_read_bool(node, "google,has-vbc-nvram")) {
> > +               retval = mfd_add_devices(ec->dev, PLATFORM_DEVID_AUTO,
> > +                                        cros_ec_vbc_cells,
> > +                                        ARRAY_SIZE(cros_ec_vbc_cells),
> > +                                        NULL, 0, NULL);
> > +               if (retval)
> > +                       dev_warn(ec->dev, "failed to add VBC devices: %d\n",
> > +                                retval);
> > +       }
> > +
> >         return 0;
> >
> >  failed:
> > diff --git a/drivers/platform/chrome/cros_ec_vbc.c b/drivers/platform/chrome/cros_ec_vbc.c
> > index da3bbf05e86f..af9bfe6f385c 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)
> > --
> > 2.19.1
> >