Re: [PATCH 5/7] mfd / platform: cros_ec: move device sysfs attributes to its own driver.

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Nov 22, 2018 at 12:33:54PM +0100, Enric Balletbo i Serra wrote:
> The entire way how cros debugfs attibutes are created is broken.
> cros_ec_sysfs should be its own driver and its attributes should be
> associated with the sysfs driver not the mfd driver.
> 
> The patch also adds the sysfs documentation.
> 
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> ---
> 
>  .../ABI/testing/sysfs-class-chromeos          | 32 ++++++++++++++
>  drivers/mfd/Kconfig                           |  1 -
>  drivers/mfd/cros_ec_dev.c                     |  7 +--
>  drivers/platform/chrome/Kconfig               | 14 ++++--
>  drivers/platform/chrome/Makefile              |  3 +-
>  drivers/platform/chrome/cros_ec_sysfs.c       | 43 ++++++++++++++++++-
>  include/linux/mfd/cros_ec.h                   |  3 --
>  7 files changed, 87 insertions(+), 16 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-chromeos
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-chromeos b/Documentation/ABI/testing/sysfs-class-chromeos
> new file mode 100644
> index 000000000000..a5399c4ca82d
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-chromeos
> @@ -0,0 +1,32 @@
> +What:		/sys/class/chromeos/<cros-ec>/flashinfo
> +Date:		August 2015
> +KernelVersion:	4.2
> +Description:
> +		Show the EC flash information.
> +
> +What:		/sys/class/chromeos/<cros-ec>/kb_wake_angle
> +Date:		March 2018
> +KernelVersion:	4.17
> +Description:
> +		Control the keyboard wake lid angle. Values are between
> +		0 and 360. This file will also show the keyboard wake lid
> +		angle by querying the hardware.
> +
> +What:		/sys/class/chromeos/<cros-ec>/reboot
> +Date:		August 2015
> +KernelVersion:	4.2
> +Description:
> +		Tell the EC to reboot in various ways. Options are:
> +		"cancel": Cancel a pending reboot.
> +		"ro": Jump to RO without rebooting.
> +		"rw": Jump to RW without rebooting.
> +		"cold": Cold reboot.
> +		"disable-jump": Disable jump until next reboot.
> +		"hibernate": Hibernate the EC.
> +		"at-shutdown": Reboot after an AP shutdown.
> +
> +What:		/sys/class/chromeos/<cros-ec>/version
> +Date:		August 2015
> +KernelVersion:	4.2
> +Description:
> +		Show the information about the EC software and hardware.
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 8c5dfdce4326..089ffb408918 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -214,7 +214,6 @@ config MFD_CROS_EC
>  config MFD_CROS_EC_CHARDEV
>          tristate "Chrome OS Embedded Controller userspace device interface"
>          depends on MFD_CROS_EC
> -        select CROS_EC_CTL
>          ---help---
>            This driver adds support to talk with the ChromeOS EC from userspace.
>  
> diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
> index 8c7ee2a0b50a..fc235af6da65 100644
> --- a/drivers/mfd/cros_ec_dev.c
> +++ b/drivers/mfd/cros_ec_dev.c
> @@ -34,15 +34,9 @@
>  #define CROS_MAX_DEV 128
>  static int ec_major;
>  
> -static const struct attribute_group *cros_ec_groups[] = {
> -	&cros_ec_attr_group,
> -	NULL,
> -};
> -
>  static struct class cros_class = {
>  	.owner          = THIS_MODULE,
>  	.name           = "chromeos",
> -	.dev_groups     = cros_ec_groups,
>  };
>  
>  int cros_ec_attach_attribute_group(struct cros_ec_dev *ec,
> @@ -405,6 +399,7 @@ static const struct mfd_cell cros_usbpd_charger_cells[] = {
>  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" },
>  };
>  
> diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
> index a1239d48c46f..2ef51520766a 100644
> --- a/drivers/platform/chrome/Kconfig
> +++ b/drivers/platform/chrome/Kconfig
> @@ -49,9 +49,6 @@ config CHROMEOS_TBMC
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called chromeos_tbmc.
>  
> -config CROS_EC_CTL
> -        tristate
> -
>  config CROS_EC_I2C
>  	tristate "ChromeOS Embedded Controller (I2C)"
>  	depends on MFD_CROS_EC && I2C
> @@ -141,4 +138,15 @@ config CROS_EC_DEBUGFS
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called cros_ec_debugfs.
>  
> +config CROS_EC_SYSFS
> +	tristate "ChromeOS EC control and information through sysfs"
> +	depends on MFD_CROS_EC_CHARDEV && SYSFS
> +	default y
> +	help
> +	  This option exposes some sysfs attributes to control and get
> +	  information from ChromeOS EC.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called cros_ec_sysfs.
> +
>  endif # CHROMEOS_PLATFORMS
> diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
> index 12a5c4d18c17..fdbee501931b 100644
> --- a/drivers/platform/chrome/Makefile
> +++ b/drivers/platform/chrome/Makefile
> @@ -3,8 +3,6 @@
>  obj-$(CONFIG_CHROMEOS_LAPTOP)		+= chromeos_laptop.o
>  obj-$(CONFIG_CHROMEOS_PSTORE)		+= chromeos_pstore.o
>  obj-$(CONFIG_CHROMEOS_TBMC)		+= chromeos_tbmc.o
> -cros_ec_ctl-objs			:= cros_ec_sysfs.o
> -obj-$(CONFIG_CROS_EC_CTL)		+= cros_ec_ctl.o
>  obj-$(CONFIG_CROS_EC_I2C)		+= cros_ec_i2c.o
>  obj-$(CONFIG_CROS_EC_SPI)		+= cros_ec_spi.o
>  cros_ec_lpcs-objs			:= cros_ec_lpc.o cros_ec_lpc_reg.o
> @@ -15,3 +13,4 @@ obj-$(CONFIG_CROS_KBD_LED_BACKLIGHT)	+= cros_kbd_led_backlight.o
>  obj-$(CONFIG_CROS_EC_LIGHTBAR)		+= cros_ec_lightbar.o
>  obj-$(CONFIG_CROS_EC_VBC)		+= cros_ec_vbc.o
>  obj-$(CONFIG_CROS_EC_DEBUGFS)		+= cros_ec_debugfs.o
> +obj-$(CONFIG_CROS_EC_SYSFS)		+= cros_ec_sysfs.o
> diff --git a/drivers/platform/chrome/cros_ec_sysfs.c b/drivers/platform/chrome/cros_ec_sysfs.c
> index f34a50121064..47d08a8f0542 100644
> --- a/drivers/platform/chrome/cros_ec_sysfs.c
> +++ b/drivers/platform/chrome/cros_ec_sysfs.c
> @@ -34,6 +34,8 @@
>  #include <linux/types.h>
>  #include <linux/uaccess.h>
>  
> +#define DRV_NAME "cros-ec-sysfs"
> +
>  /* Accessor functions */
>  
>  static ssize_t reboot_show(struct device *dev,
> @@ -353,7 +355,46 @@ struct attribute_group cros_ec_attr_group = {
>  	.attrs = __ec_attrs,
>  	.is_visible = cros_ec_ctrl_visible,

I think the .is_visible evaluation should now happen in the probe fuction.

>  };
> -EXPORT_SYMBOL(cros_ec_attr_group);
> +
> +static int cros_ec_sysfs_probe(struct platform_device *pd)
> +{
> +	struct cros_ec_dev *ec_dev = dev_get_drvdata(pd->dev.parent);
> +	struct cros_ec_platform *ec_platform = dev_get_platdata(ec_dev->dev);
> +	struct device *dev = &pd->dev;
> +	int ret;
> +
> +	if (!ec_dev) {
> +		dev_err(dev, "No EC dev found\n");
> +		return -EINVAL;
> +	}

Above:

	struct cros_ec_platform *ec_platform = dev_get_platdata(ec_dev->dev);

so if ec_dev is ever NULL, we'll never get to this point (and static
analyzers will have a field day). I think the check is unnecessary.

> +
> +	ret = cros_ec_attach_attribute_group(ec_dev, &cros_ec_attr_group);
> +	if (ret < 0)
> +		dev_err(dev, "failed to create %s attributes. err=%d\n",
> +			ec_platform->ec_name, ret);

Does it really make sense to display ec_platform->ec_name here ?
"Failed to create sysfs attributes" with dev_err should be good enough.

Also, again, I think we should create the attribute directly and drop
cros_ec_attach_attribute_group().

> +
> +	return ret;
> +}
> +
> +static int cros_ec_sysfs_remove(struct platform_device *pd)
> +{
> +	struct cros_ec_dev *ec_dev = dev_get_drvdata(pd->dev.parent);
> +
> +	cros_ec_detach_attribute_group(ec_dev, &cros_ec_attr_group);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver cros_ec_sysfs_driver = {
> +	.driver = {
> +		.name = DRV_NAME,
> +	},
> +	.probe = cros_ec_sysfs_probe,
> +	.remove = cros_ec_sysfs_remove,
> +};
> +
> +module_platform_driver(cros_ec_sysfs_driver);
>  
>  MODULE_LICENSE("GPL");
>  MODULE_DESCRIPTION("ChromeOS EC control driver");
> +MODULE_ALIAS("platform:" DRV_NAME);
> diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
> index 1722c2c26143..6d8618894a45 100644
> --- a/include/linux/mfd/cros_ec.h
> +++ b/include/linux/mfd/cros_ec.h
> @@ -333,9 +333,6 @@ int cros_ec_get_next_event(struct cros_ec_device *ec_dev, bool *wake_event);
>   */
>  u32 cros_ec_get_host_event(struct cros_ec_device *ec_dev);
>  
> -/* sysfs stuff */
> -extern struct attribute_group cros_ec_attr_group;
> -
>  /* Attach/detach attributes to the cros_class */
>  extern int cros_ec_attach_attribute_group(struct cros_ec_dev *ec,
>  					  struct attribute_group *attrs);