Re: [PATCH] platform/x86: thinkpad_acpi: sysfs interface to auxmac

[Hans de Goede]

Hi Fernando,

On 9/6/23 21:52, Fernando Eckhardt Valle wrote:
> Newer Thinkpads have a feature called Mac Address Passthrough.
> This patch provides a sysfs interface that userspace can use
> to get this auxiliary mac address.
> 
> Signed-off-by: Fernando Eckhardt Valle <fevalle@xxxxxx>

Thank you for your patch. 

At a minimum for this patch to be accepted you will need
to document the new sysfs interface in:

Documentation/admin-guide/laptops/thinkpad-acpi.rst

But I wonder if we should export this information to
userspace in this way ?

The reason why I'm wondering is because mac-address passthrough
in case of using e.g. Lenovo Thunderbolt docks is already
supported by the kernel by code for this in drivers/net/usb/r8152.c :

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/usb/r8152.c#n1613

So I'm wondering if we really need this, is there a planned
userspace API consumer of the new sysfs interface ?

Or is this only intended as a way for a user to query this, iow
is this purely intended for informational purposes ?

Regards,

Hans






> ---
>  drivers/platform/x86/thinkpad_acpi.c | 77 ++++++++++++++++++++++++++++
>  1 file changed, 77 insertions(+)
> 
> diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
> index d70c89d32..0b1c36b0d 100644
> --- a/drivers/platform/x86/thinkpad_acpi.c
> +++ b/drivers/platform/x86/thinkpad_acpi.c
> @@ -10785,6 +10785,78 @@ static struct ibm_struct dprc_driver_data = {
>  	.name = "dprc",
>  };
>  
> +/*
> + * Auxmac
> + *
> + * This auxiliary mac address is enabled in the bios through the
> + * Mac Address Passthrough feature. In most cases, there are three
> + * possibilities: Internal Mac, Second Mac, and disabled.
> + *
> + */
> +
> +#define AUXMAC_LEN 12
> +#define AUXMAC_START 9
> +#define AUXMAC_STRLEN 22
> +static char auxmac[AUXMAC_LEN];
> +
> +static int auxmac_init(struct ibm_init_struct *iibm)
> +{
> +	acpi_status status;
> +	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> +	union acpi_object *obj;
> +
> +	status = acpi_evaluate_object(NULL, "\\MACA", NULL, &buffer);
> +
> +	if (ACPI_FAILURE(status))
> +		return -ENODEV;
> +
> +	obj = (union acpi_object *)buffer.pointer;
> +
> +	if (obj->type != ACPI_TYPE_STRING || obj->string.length != AUXMAC_STRLEN) {
> +		pr_info("Invalid buffer for mac addr passthrough.\n");
> +		goto auxmacinvalid;
> +	}
> +
> +	if (strncmp(obj->string.pointer + 0x8, "#", 1) != 0 ||
> +	    strncmp(obj->string.pointer + 0x15, "#", 1) != 0) {
> +		pr_info("Invalid header for mac addr passthrough.\n");
> +		goto auxmacinvalid;
> +	}
> +
> +	memcpy(auxmac, obj->string.pointer + AUXMAC_START, AUXMAC_LEN);
> +	kfree(obj);
> +	return 0;
> +
> +auxmacinvalid:
> +	kfree(obj);
> +	memcpy(auxmac, "unavailable", 11);
> +	return 0;
> +}
> +
> +static struct ibm_struct auxmac_data = {
> +	.name = "auxmac",
> +};
> +
> +static ssize_t auxmac_show(struct device *dev,
> +			   struct device_attribute *attr,
> +			   char *buf)
> +{
> +	if (strncmp(auxmac, "XXXXXXXXXXXX", AUXMAC_LEN) == 0)
> +		memcpy(auxmac, "disabled", 9);
> +
> +	return sysfs_emit(buf, "%s\n", auxmac);
> +}
> +static DEVICE_ATTR_RO(auxmac);
> +
> +static struct attribute *auxmac_attributes[] = {
> +	&dev_attr_auxmac.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group auxmac_attr_group = {
> +	.attrs = auxmac_attributes,
> +};
> +
>  /* --------------------------------------------------------------------- */
>  
>  static struct attribute *tpacpi_driver_attributes[] = {
> @@ -10843,6 +10915,7 @@ static const struct attribute_group *tpacpi_groups[] = {
>  	&proxsensor_attr_group,
>  	&kbdlang_attr_group,
>  	&dprc_attr_group,
> +	&auxmac_attr_group,
>  	NULL,
>  };
>  
> @@ -11414,6 +11487,10 @@ static struct ibm_init_struct ibms_init[] __initdata = {
>  		.init = tpacpi_dprc_init,
>  		.data = &dprc_driver_data,
>  	},
> +	{
> +		.init = auxmac_init,
> +		.data = &auxmac_data,
> +	},
>  };
>  
>  static int __init set_ibm_param(const char *val, const struct kernel_param *kp)