[PATCH v2 1/1] x86/PCI: Clean up open-coded return code mangling

From: Ilpo Järvinen
Date: Fri Oct 27 2023 - 05:32:41 EST


PCI BIOS gives a return code in 8 bits of eax register which is
extracted by open-coded masks and shifting.

Name the return code bits with a define and introduce
pcibios_get_return_code() helper to extract the return code to improve
code readability. In addition, replace a zero test with
PCIBIOS_SUCCESSFUL.

No function changes intended.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
---

v2:
- Improve changelog
- Add helper to avoid repeating FIELD_GET()
- Reuse existing ret variable in pcibios_get_irq_routing_table()

arch/x86/pci/pcbios.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/arch/x86/pci/pcbios.c b/arch/x86/pci/pcbios.c
index 4f15280732ed..01c94ac2fb70 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>
@@ -29,8 +31,19 @@
#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;

+static u8 pcibios_get_return_code(u32 eax)
+{
+ return FIELD_GET(PCIBIOS_RETURN_CODE, eax);
+}
+
/* According to the BIOS specification at:
* http://members.datafast.net.au/dft0802/specs/bios21.pdf, we could
* restrict the x zone to some pages and make it ro. But this may be
@@ -154,7 +167,7 @@ static int __init check_pcibios(void)
: "memory");
local_irq_restore(flags);

- status = (eax >> 8) & 0xff;
+ status = pcibios_get_return_code(eax);
hw_mech = eax & 0xff;
major_ver = (ebx >> 8) & 0xff;
minor_ver = ebx & 0xff;
@@ -227,7 +240,7 @@ 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 pcibios_get_return_code(result);
}

static int pci_bios_write(unsigned int seg, unsigned int bus,
@@ -269,7 +282,7 @@ 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 pcibios_get_return_code(result);
}


@@ -385,8 +398,9 @@ 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);
+ ret = pcibios_get_return_code(ret);
+ if (ret)
+ printk(KERN_ERR "PCI: Error %02x when fetching IRQ routing table.\n", ret);
else if (opt.size) {
rt = kmalloc(sizeof(struct irq_routing_table) + opt.size, GFP_KERNEL);
if (rt) {
@@ -415,7 +429,7 @@ 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 pcibios_get_return_code(ret) == PCIBIOS_SUCCESSFUL;
}
EXPORT_SYMBOL(pcibios_set_irq_routing);

--
2.30.2