dmaengine: idxd: Allow ATS disable update only for configurable devices

ATS disable status in a WQ is read-only if the device is not configurable.
This change ensures that the ATS disable attribute can be modified via
sysfs only on configurable devices.

Fixes: 92de5fa ("dmaengine: idxd: add ATS disable knob for work queues")
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20230811012635.535413-1-fenghua.yu@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: Fenghua Yu

drivers/dma/idxd/sysfs.c

@@ -1088,12 +1088,16 @@ static ssize_t wq_ats_disable_store(struct device *dev, struct device_attribute
 				    const char *buf, size_t count)
 {
 	struct idxd_wq *wq = confdev_to_wq(dev);
+	struct idxd_device *idxd = wq->idxd;
 	bool ats_dis;
 	int rc;
 
 	if (wq->state != IDXD_WQ_DISABLED)
 		return -EPERM;
 
+	if (!test_bit(IDXD_FLAG_CONFIGURABLE, &idxd->flags))
+		return -EPERM;
+
 	rc = kstrtobool(buf, &ats_dis);
 	if (rc < 0)
 		return rc;