[PATCH v1] ACPI: sysfs: Add device cid attribute for exposing _CID lists

Posted by Rafael J. Wysocki 1 month, 3 weeks ago

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Add a new sysfs attribute called "cid" under struct acpi_device for
exposing the list of compatible device IDs returned by the device's
_CID object, if present.

The new attribute will be present only if the _CID object is present.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/device_sysfs.c |   31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

--- a/drivers/acpi/device_sysfs.c
+++ b/drivers/acpi/device_sysfs.c
@@ -403,6 +403,33 @@ hid_show(struct device *dev, struct devi
 }
 static DEVICE_ATTR_RO(hid);
 
+static ssize_t cid_show(struct device *dev, struct device_attribute *attr,
+			char *buf)
+{
+	struct acpi_device *acpi_dev = to_acpi_device(dev);
+	struct acpi_device_info *info = NULL;
+	ssize_t len = 0;
+
+	acpi_get_object_info(acpi_dev->handle, &info);
+	if (!info)
+		return 0;
+
+	if (info->valid & ACPI_VALID_CID) {
+		struct acpi_pnp_device_id_list *cid_list = &info->compatible_id_list;
+		int i;
+
+		for (i = 0; i < cid_list->count - 1; i++)
+			len += sysfs_emit(buf, "%s,", cid_list->ids[i].string);
+
+		len += sysfs_emit(buf, "%s\n", cid_list->ids[i].string);
+	}
+
+	kfree(info);
+
+	return len;
+}
+static DEVICE_ATTR_RO(cid);
+
 static ssize_t uid_show(struct device *dev,
 			struct device_attribute *attr, char *buf)
 {
@@ -520,6 +547,7 @@ static DEVICE_ATTR_RO(status);
 static struct attribute *acpi_attrs[] = {
 	&dev_attr_path.attr,
 	&dev_attr_hid.attr,
+	&dev_attr_cid.attr,
 	&dev_attr_modalias.attr,
 	&dev_attr_description.attr,
 	&dev_attr_adr.attr,
@@ -562,6 +590,9 @@ static bool acpi_show_attr(struct acpi_d
 	if (attr == &dev_attr_status)
 		return acpi_has_method(dev->handle, "_STA");
 
+	if (attr == &dev_attr_cid)
+		return acpi_has_method(dev->handle, "_CID");
+
 	/*
 	 * If device has _EJ0, 'eject' file is created that is used to trigger
 	 * hot-removal function from userland.

Re: [PATCH v1] ACPI: sysfs: Add device cid attribute for exposing _CID lists

Posted by Andy Shevchenko 1 month, 1 week ago

On Fri, Dec 12, 2025 at 09:52:44PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> Add a new sysfs attribute called "cid" under struct acpi_device for
> exposing the list of compatible device IDs returned by the device's
> _CID object, if present.
> 
> The new attribute will be present only if the _CID object is present.

...

> +static ssize_t cid_show(struct device *dev, struct device_attribute *attr,
> +			char *buf)
> +{
> +	struct acpi_device *acpi_dev = to_acpi_device(dev);
> +	struct acpi_device_info *info = NULL;
> +	ssize_t len = 0;
> +
> +	acpi_get_object_info(acpi_dev->handle, &info);
> +	if (!info)
> +		return 0;
> +
> +	if (info->valid & ACPI_VALID_CID) {
> +		struct acpi_pnp_device_id_list *cid_list = &info->compatible_id_list;
> +		int i;
> +
> +		for (i = 0; i < cid_list->count - 1; i++)
> +			len += sysfs_emit(buf, "%s,", cid_list->ids[i].string);
> +
> +		len += sysfs_emit(buf, "%s\n", cid_list->ids[i].string);

You definitely meant to use sysfs_emit_at().

> +	}
> +
> +	kfree(info);
> +
> +	return len;
> +}
> +static DEVICE_ATTR_RO(cid);

Do wee have any ABI documentation for these sysfs attributes?
If so, it needs to be updated, otherwise perhaps create one?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v1] ACPI: sysfs: Add device cid attribute for exposing _CID lists

Posted by Rafael J. Wysocki 1 month, 1 week ago

On Sun, Dec 28, 2025 at 9:19 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Fri, Dec 12, 2025 at 09:52:44PM +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > Add a new sysfs attribute called "cid" under struct acpi_device for
> > exposing the list of compatible device IDs returned by the device's
> > _CID object, if present.
> >
> > The new attribute will be present only if the _CID object is present.
>
> ...
>
> > +static ssize_t cid_show(struct device *dev, struct device_attribute *attr,
> > +                     char *buf)
> > +{
> > +     struct acpi_device *acpi_dev = to_acpi_device(dev);
> > +     struct acpi_device_info *info = NULL;
> > +     ssize_t len = 0;
> > +
> > +     acpi_get_object_info(acpi_dev->handle, &info);
> > +     if (!info)
> > +             return 0;
> > +
> > +     if (info->valid & ACPI_VALID_CID) {
> > +             struct acpi_pnp_device_id_list *cid_list = &info->compatible_id_list;
> > +             int i;
> > +
> > +             for (i = 0; i < cid_list->count - 1; i++)
> > +                     len += sysfs_emit(buf, "%s,", cid_list->ids[i].string);
> > +
> > +             len += sysfs_emit(buf, "%s\n", cid_list->ids[i].string);
>
> You definitely meant to use sysfs_emit_at().

Right, thanks!

> > +     }
> > +
> > +     kfree(info);
> > +
> > +     return len;
> > +}
> > +static DEVICE_ATTR_RO(cid);
>
> Do wee have any ABI documentation for these sysfs attributes?

No, there's none I know of.

> If so, it needs to be updated, otherwise perhaps create one?

Well, feel free to do so.