[PATCH 1/1] x86/PCI: Name PCI BIOS error code & use FIELD_GET()

[Ilpo Järvinen]

PCI BIOS returns error code in AH register when carry flag is set. The
extraction of the error code is currently set of masking and shifting
which makes the code harder to understand than it needs to be.

Name the PCI BIOS error code with a define and use FIELD_GET() to
access it to improve code readability.

In addition, rely on implicit cast to int and replace zero test
with PCIBIOS_SUCCESSFUL.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
---
 arch/x86/pci/pcbios.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/arch/x86/pci/pcbios.c b/arch/x86/pci/pcbios.c
index 4f15280732ed..0515e0c05e10 100644
--- a/arch/x86/pci/pcbios.c
+++ b/arch/x86/pci/pcbios.c
@@ -3,6 +3,8 @@
  * BIOS32 and PCI BIOS handling.
  */
 
+#include <linux/bits.h>
+#include <linux/bitfield.h>
 #include <linux/pci.h>
 #include <linux/init.h>
 #include <linux/slab.h>
@@ -29,6 +31,12 @@
 #define PCIBIOS_HW_TYPE1_SPEC		0x10
 #define PCIBIOS_HW_TYPE2_SPEC		0x20
 
+/*
+ * Returned in EAX:
+ * - AH: return code
+ */
+#define PCIBIOS_RETURN_CODE			GENMASK(15, 8)
+
 int pcibios_enabled;
 
 /* According to the BIOS specification at:
@@ -154,7 +162,7 @@ static int __init check_pcibios(void)
 			: "memory");
 		local_irq_restore(flags);
 
-		status = (eax >> 8) & 0xff;
+		status = FIELD_GET(PCIBIOS_RETURN_CODE, eax);
 		hw_mech = eax & 0xff;
 		major_ver = (ebx >> 8) & 0xff;
 		minor_ver = ebx & 0xff;
@@ -227,7 +235,7 @@ static int pci_bios_read(unsigned int seg, unsigned int bus,
 
 	raw_spin_unlock_irqrestore(&pci_config_lock, flags);
 
-	return (int)((result & 0xff00) >> 8);
+	return FIELD_GET(PCIBIOS_RETURN_CODE, result);
 }
 
 static int pci_bios_write(unsigned int seg, unsigned int bus,
@@ -269,7 +277,7 @@ static int pci_bios_write(unsigned int seg, unsigned int bus,
 
 	raw_spin_unlock_irqrestore(&pci_config_lock, flags);
 
-	return (int)((result & 0xff00) >> 8);
+	return FIELD_GET(PCIBIOS_RETURN_CODE, result);
 }
 
 
@@ -354,6 +362,7 @@ struct irq_routing_table * pcibios_get_irq_routing_table(void)
 {
 	struct irq_routing_options opt;
 	struct irq_routing_table *rt = NULL;
+	unsigned int error_code;
 	int ret, map;
 	unsigned long page;
 
@@ -385,8 +394,9 @@ struct irq_routing_table * pcibios_get_irq_routing_table(void)
 		  "m" (opt)
 		: "memory");
 	DBG("OK  ret=%d, size=%d, map=%x\n", ret, opt.size, map);
-	if (ret & 0xff00)
-		printk(KERN_ERR "PCI: Error %02x when fetching IRQ routing table.\n", (ret >> 8) & 0xff);
+	error_code = FIELD_GET(PCIBIOS_RETURN_CODE, ret);
+	if (error_code)
+		printk(KERN_ERR "PCI: Error %02x when fetching IRQ routing table.\n", error_code);
 	else if (opt.size) {
 		rt = kmalloc(sizeof(struct irq_routing_table) + opt.size, GFP_KERNEL);
 		if (rt) {
@@ -415,7 +425,7 @@ int pcibios_set_irq_routing(struct pci_dev *dev, int pin, int irq)
 		  "b" ((dev->bus->number << 8) | dev->devfn),
 		  "c" ((irq << 8) | (pin + 10)),
 		  "S" (&pci_indirect));
-	return !(ret & 0xff00);
+	return FIELD_GET(PCIBIOS_RETURN_CODE, ret) == PCIBIOS_SUCCESSFUL;
 }
 EXPORT_SYMBOL(pcibios_set_irq_routing);
 
-- 
2.30.2