Re: [PATCH 2/2] platform/x86: firmware_attributes_class: Add test driver

[Mario Limonciello <mario.limonciello@amd.com>]

On 1/7/2025 11:05, Thomas Weißschuh wrote:
> The driver showcases the use of the new subsystem API.
> 
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> ---
>   drivers/platform/x86/Kconfig                    | 12 ++++
>   drivers/platform/x86/Makefile                   |  1 +
>   drivers/platform/x86/firmware_attributes_test.c | 78 +++++++++++++++++++++++++
>   3 files changed, 91 insertions(+)
> 
> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> index 0258dd879d64be389f4dd9bc309fe089f23cc798..2a0e828657d2f07074944d6c42dc204fc8825a42 100644
> --- a/drivers/platform/x86/Kconfig
> +++ b/drivers/platform/x86/Kconfig
> @@ -1065,6 +1065,18 @@ source "drivers/platform/x86/x86-android-tablets/Kconfig"
>   config FW_ATTR_CLASS
>   	tristate
>   
> +config FW_ATTR_TEST
> +	tristate "Firmware attribute test driver"
> +	select FW_ATTR_CLASS
> +	help
> +	  This driver provides a test user of the firmware attribute subsystem.
> +
> +	  An instance is created at /sys/class/firmware-attributes/test/
> +	  container various example attributes.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called firmware_attributes_test.
> +

I think if you're going to be introducing a test driver it should be 
compliant to what's in sysfs-class-firmware-attributes so that when it's 
inevitably copy/pasted we end up with higher quality drivers.

That is you need at a minimum 'type', 'current_value', 'default_value', 
'display_name' and 'display_name_language_code'.  Then individual types 
employ additional requirements.

I see 'type', 'current_value', and 'default_value, but I don't see 
'display_name' or 'display_name_language_code' here.

Furthermore as this is a "string" attribute you're supposed to also have 
a "max_length" and "min_length".

>   config INTEL_IMR
>   	bool "Intel Isolated Memory Region support"
>   	depends on X86_INTEL_QUARK && IOSF_MBI
> diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
> index e1b142947067475ee5472400a5a1cd20d79e12bd..610a1ca850a4353fd490e43b214a9e5872d2d28d 100644
> --- a/drivers/platform/x86/Makefile
> +++ b/drivers/platform/x86/Makefile
> @@ -121,6 +121,7 @@ obj-$(CONFIG_TOPSTAR_LAPTOP)	+= topstar-laptop.o
>   
>   # Platform drivers
>   obj-$(CONFIG_FW_ATTR_CLASS)		+= firmware_attributes_class.o
> +obj-$(CONFIG_FW_ATTR_TEST)		+= firmware_attributes_test.o
>   obj-$(CONFIG_SERIAL_MULTI_INSTANTIATE)	+= serial-multi-instantiate.o
>   obj-$(CONFIG_MLX_PLATFORM)		+= mlx-platform.o
>   obj-$(CONFIG_TOUCHSCREEN_DMI)		+= touchscreen_dmi.o
> diff --git a/drivers/platform/x86/firmware_attributes_test.c b/drivers/platform/x86/firmware_attributes_test.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..84f6a92e5163378c655f30ac022d513d7df5a18c
> --- /dev/null
> +++ b/drivers/platform/x86/firmware_attributes_test.c
> @@ -0,0 +1,78 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include <linux/module.h>
> +#include <linux/sysfs.h>
> +#include "firmware_attributes_class.h"
> +
> +struct fw_attr_test_data {
> +	char attr1_value[PAGE_SIZE];
> +};
> +
> +static ssize_t test_attr1_default_value_show(struct firmware_attributes_device *fwadev,
> +					     const struct firmware_attribute *attr, char *buf)
> +{
> +	return sysfs_emit(buf, "default 1\n");
> +}
> +
> +static struct firmware_attribute test_attr1_default_value = __ATTR(default_value, 0444,
> +								   test_attr1_default_value_show,
> +								   NULL);
> +
> +static ssize_t test_attr1_current_value_show(struct firmware_attributes_device *fwadev,
> +					     const struct firmware_attribute *attr, char *buf)
> +{
> +	struct fw_attr_test_data *data = fwadev->data;
> +
> +	return sysfs_emit(buf, "%s\n", data->attr1_value);
> +}
> +
> +static ssize_t test_attr1_current_value_store(struct firmware_attributes_device *fwadev,
> +					      const struct firmware_attribute *attr,
> +					      const char *buf, size_t count)
> +{
> +	struct fw_attr_test_data *data = fwadev->data;
> +
> +	return strscpy(data->attr1_value, buf);
> +}
> +
> +static struct firmware_attribute test_attr1_current_value = __ATTR(current_value, 0644,
> +								   test_attr1_current_value_show,
> +								   test_attr1_current_value_store);
> +
> +static struct attribute *test_attr1_attrs[] = {
> +	firmware_attribute_type_string,
> +	&test_attr1_default_value.attr,
> +	&test_attr1_current_value.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group test_attr1_group = {
> +	.name	= "attr1",
> +	.attrs	= test_attr1_attrs,
> +};
> +
> +static const struct attribute_group *test_attr_groups[] = {
> +	&test_attr1_group,
> +	NULL
> +};
> +
> +static struct firmware_attributes_device *fwadev;
> +
> +static int __init fw_test_init(void)
> +{
> +	static struct fw_attr_test_data data = {
> +		.attr1_value = "attr1",
> +	};
> +
> +	fwadev = firmware_attributes_device_register(NULL, "test", test_attr_groups, &data);
> +	return PTR_ERR_OR_ZERO(fwadev);
> +}
> +module_init(fw_test_init);
> +
> +static void __exit fw_test_exit(void)
> +{
> +	firmware_attributes_device_unregister(fwadev);
> +}
> +module_exit(fw_test_exit);
> +
> +MODULE_LICENSE("GPL");
>