crypto: qat - add num_rps sysfs attribute

Add the attribute `num_rps` to the `qat` attribute group. This returns
the number of ring pairs that a single device has. This allows to know
the maximum value that can be set to the attribute `rp2svc`.
Signed-off-by: Ciunas Bennett <ciunas.bennett@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Damian Muszynski <damian.muszynski@intel.com>
Reviewed-by: Tero Kristo <tero.kristo@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Documentation/ABI/testing/sysfs-driver-qat

@@ -127,3 +127,17 @@ Description:
 			sym
 
 		This attribute is only available for qat_4xxx devices.
+
+What:		/sys/bus/pci/devices/<BDF>/qat/num_rps
+Date:		January 2024
+KernelVersion:	6.7
+Contact:	qat-linux@intel.com
+Description:
+		(RO) Returns the number of ring pairs that a single device has.
+
+		Example usage::
+
+			# cat /sys/bus/pci/devices/<BDF>/qat/num_rps
+			64
+
+		This attribute is only available for qat_4xxx devices.

drivers/crypto/intel/qat/qat_common/adf_sysfs.c

@@ -268,11 +268,25 @@ static ssize_t rp2srv_store(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RW(rp2srv);
 
+static ssize_t num_rps_show(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	struct adf_accel_dev *accel_dev;
+
+	accel_dev = adf_devmgr_pci_to_accel_dev(to_pci_dev(dev));
+	if (!accel_dev)
+		return -EINVAL;
+
+	return sysfs_emit(buf, "%u\n", GET_MAX_BANKS(accel_dev));
+}
+static DEVICE_ATTR_RO(num_rps);
+
 static struct attribute *qat_attrs[] = {
 	&dev_attr_state.attr,
 	&dev_attr_cfg_services.attr,
 	&dev_attr_pm_idle_enabled.attr,
 	&dev_attr_rp2srv.attr,
+	&dev_attr_num_rps.attr,
 	NULL,
 };