linux-kernel - [PATCH v8 4/6] PCI/ERR: simplify function pci_dev_set_io

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Date:   Wed,  7 Oct 2020 07:31:56 -0400
From:   Ethan Zhao <haifeng.zhao@...el.com>
To:     bhelgaas@...gle.com, oohall@...il.com, ruscur@...sell.cc,
        lukas@...ner.de, andriy.shevchenko@...ux.intel.com,
        stuart.w.hayes@...il.com, mr.nuke.me@...il.com,
        mika.westerberg@...ux.intel.com
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        ashok.raj@...ux.intel.com, sathyanarayanan.kuppuswamy@...el.com,
        xerces.zhao@...il.com, Ethan Zhao <haifeng.zhao@...el.com>
Subject: [PATCH v8 4/6] PCI/ERR: simplify function pci_dev_set_io_state() with if

No function change.

Signed-off-by: Ethan Zhao <haifeng.zhao@...el.com>
---
Changes:
 v8: based on Bjorn's code and truth table, simplify the logic of
function pci_dev_set_io_state(), no function change.

 drivers/pci/pci.h | 54 ++++++++++++++++++++---------------------------
 1 file changed, 23 insertions(+), 31 deletions(-)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 455b32187abd..bceb3f108744 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -359,39 +359,31 @@ struct pci_sriov {
 static inline bool pci_dev_set_io_state(struct pci_dev *dev,
 					pci_channel_state_t new)
 {
-	bool changed = false;
-
 	device_lock_assert(&dev->dev);
-	switch (new) {
-	case pci_channel_io_perm_failure:
-		switch (dev->error_state) {
-		case pci_channel_io_frozen:
-		case pci_channel_io_normal:
-		case pci_channel_io_perm_failure:
-			changed = true;
-			break;
-		}
-		break;
-	case pci_channel_io_frozen:
-		switch (dev->error_state) {
-		case pci_channel_io_frozen:
-		case pci_channel_io_normal:
-			changed = true;
-			break;
-		}
-		break;
-	case pci_channel_io_normal:
-		switch (dev->error_state) {
-		case pci_channel_io_frozen:
-		case pci_channel_io_normal:
-			changed = true;
-			break;
-		}
-		break;
+/*
+ *                     Truth table:
+ *                     requested new state
+ *     current          ------------------------------------------
+ *     state            normal         frozen         perm_failure
+ *     ------------  +  -------------  -------------  ------------
+ *     normal        |  normal         frozen         perm_failure
+ *     frozen        |  normal         frozen         perm_failure
+ *     perm_failure  |  perm_failure*  perm_failure*  perm_failure
+ */
+
+	/* Can always put a device in perm_failure state */
+	if (new == pci_channel_io_perm_failure) {
+		dev->error_state = pci_channel_io_perm_failure;
+		return true;
 	}
-	if (changed)
-		dev->error_state = new;
-	return changed;
+
+	/* If already in perm_failure, can't set to normal or frozen */
+	if (dev->error_state == pci_channel_io_perm_failure)
+		return false;
+
+	 /* Can always change normal to frozen or vice versa */
+	dev->error_state = new;
+	return true;
 }
 
 static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused)
-- 
2.18.4