PCI/sysfs: Use sysfs_emit() and sysfs_emit_at() in "show" functions

The sysfs_emit() and sysfs_emit_at() functions were introduced to make it
less ambiguous which function is preferred when writing to the output
buffer in a device attribute's "show" callback [1].

Convert the PCI sysfs object "show" functions from sprintf(), snprintf()
and scnprintf() to sysfs_emit() and sysfs_emit_at() accordingly, as the
latter is aware of the PAGE_SIZE buffer and correctly returns the number of
bytes written into the buffer.

No functional change intended.

[1] Documentation/filesystems/sysfs.rst

[bhelgaas: drop dsm_label_utf16s_to_utf8s(), link speed/width changes]
Link: https://lore.kernel.org/r/20210416205856.3234481-10-kw@linux.com
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci-label.c

@@ -73,12 +73,10 @@ static size_t find_smbios_instance_string(struct pci_dev *pdev, char *buf,
 				donboard->devfn == devfn) {
 			if (buf) {
 				if (attribute == SMBIOS_ATTR_INSTANCE_SHOW)
-					return scnprintf(buf, PAGE_SIZE,
+					return sysfs_emit(buf, "%d\n",
-							 "%d\n",
 							  donboard->instance);
 				else if (attribute == SMBIOS_ATTR_LABEL_SHOW)
-					return scnprintf(buf, PAGE_SIZE,
+					return sysfs_emit(buf, "%s\n",
-							 "%s\n",
 							  dmi->name);
 			}
 			return strlen(dmi->name);

drivers/pci/pci-sysfs.c

@@ -39,7 +39,7 @@ field##_show(struct device *dev, struct device_attribute *attr, char *buf)				\
 	struct pci_dev *pdev;						\
 									\
 	pdev = to_pci_dev(dev);						\
-	return sprintf(buf, format_string, pdev->field);		\
+	return sysfs_emit(buf, format_string, pdev->field);		\
 }									\
 static DEVICE_ATTR_RO(field)
 
@@ -56,7 +56,7 @@ static ssize_t broken_parity_status_show(struct device *dev,
 					 char *buf)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	return sprintf(buf, "%u\n", pdev->broken_parity_status);
+	return sysfs_emit(buf, "%u\n", pdev->broken_parity_status);
 }
 
 static ssize_t broken_parity_status_store(struct device *dev,
@@ -129,7 +129,7 @@ static ssize_t power_state_show(struct device *dev,
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 
-	return sprintf(buf, "%s\n", pci_power_name(pdev->current_state));
+	return sysfs_emit(buf, "%s\n", pci_power_name(pdev->current_state));
 }
 static DEVICE_ATTR_RO(power_state);
 
@@ -138,10 +138,10 @@ static ssize_t resource_show(struct device *dev, struct device_attribute *attr,
 			     char *buf)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
-	char *str = buf;
 	int i;
 	int max;
 	resource_size_t start, end;
+	size_t len = 0;
 
 	if (pci_dev->subordinate)
 		max = DEVICE_COUNT_RESOURCE;
@@ -151,12 +151,12 @@ static ssize_t resource_show(struct device *dev, struct device_attribute *attr,
 	for (i = 0; i < max; i++) {
 		struct resource *res =  &pci_dev->resource[i];
 		pci_resource_to_user(pci_dev, i, res, &start, &end);
-		str += sprintf(str, "0x%016llx 0x%016llx 0x%016llx\n",
+		len += sysfs_emit_at(buf, len, "0x%016llx 0x%016llx 0x%016llx\n",
 				     (unsigned long long)start,
 				     (unsigned long long)end,
 				     (unsigned long long)res->flags);
 	}
-	return (str - buf);
+	return len;
 }
 static DEVICE_ATTR_RO(resource);
 
@@ -165,7 +165,7 @@ static ssize_t max_link_speed_show(struct device *dev,
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 
-	return sprintf(buf, "%s\n",
+	return sysfs_emit(buf, "%s\n",
 			  pci_speed_string(pcie_get_speed_cap(pdev)));
 }
 static DEVICE_ATTR_RO(max_link_speed);
@@ -175,7 +175,7 @@ static ssize_t max_link_width_show(struct device *dev,
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 
-	return sprintf(buf, "%u\n", pcie_get_width_cap(pdev));
+	return sysfs_emit(buf, "%u\n", pcie_get_width_cap(pdev));
 }
 static DEVICE_ATTR_RO(max_link_width);
 
@@ -193,7 +193,7 @@ static ssize_t current_link_speed_show(struct device *dev,
 
 	speed = pcie_link_speed[linkstat & PCI_EXP_LNKSTA_CLS];
 
-	return sprintf(buf, "%s\n", pci_speed_string(speed));
+	return sysfs_emit(buf, "%s\n", pci_speed_string(speed));
 }
 static DEVICE_ATTR_RO(current_link_speed);
 
@@ -208,7 +208,7 @@ static ssize_t current_link_width_show(struct device *dev,
 	if (err)
 		return -EINVAL;
 
-	return sprintf(buf, "%u\n",
+	return sysfs_emit(buf, "%u\n",
 		(linkstat & PCI_EXP_LNKSTA_NLW) >> PCI_EXP_LNKSTA_NLW_SHIFT);
 }
 static DEVICE_ATTR_RO(current_link_width);
@@ -225,7 +225,7 @@ static ssize_t secondary_bus_number_show(struct device *dev,
 	if (err)
 		return -EINVAL;
 
-	return sprintf(buf, "%u\n", sec_bus);
+	return sysfs_emit(buf, "%u\n", sec_bus);
 }
 static DEVICE_ATTR_RO(secondary_bus_number);
 
@@ -241,7 +241,7 @@ static ssize_t subordinate_bus_number_show(struct device *dev,
 	if (err)
 		return -EINVAL;
 
-	return sprintf(buf, "%u\n", sub_bus);
+	return sysfs_emit(buf, "%u\n", sub_bus);
 }
 static DEVICE_ATTR_RO(subordinate_bus_number);
 
@@ -251,7 +251,7 @@ static ssize_t ari_enabled_show(struct device *dev,
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
 
-	return sprintf(buf, "%u\n", pci_ari_enabled(pci_dev->bus));
+	return sysfs_emit(buf, "%u\n", pci_ari_enabled(pci_dev->bus));
 }
 static DEVICE_ATTR_RO(ari_enabled);
 
@@ -260,7 +260,7 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
 
-	return sprintf(buf, "pci:v%08Xd%08Xsv%08Xsd%08Xbc%02Xsc%02Xi%02X\n",
+	return sysfs_emit(buf, "pci:v%08Xd%08Xsv%08Xsd%08Xbc%02Xsc%02Xi%02X\n",
 			  pci_dev->vendor, pci_dev->device,
 			  pci_dev->subsystem_vendor, pci_dev->subsystem_device,
 			  (u8)(pci_dev->class >> 16), (u8)(pci_dev->class >> 8),
@@ -302,7 +302,7 @@ static ssize_t enable_show(struct device *dev, struct device_attribute *attr,
 	struct pci_dev *pdev;
 
 	pdev = to_pci_dev(dev);
-	return sprintf(buf, "%u\n", atomic_read(&pdev->enable_cnt));
+	return sysfs_emit(buf, "%u\n", atomic_read(&pdev->enable_cnt));
 }
 static DEVICE_ATTR_RW(enable);
 
@@ -338,7 +338,7 @@ static ssize_t numa_node_store(struct device *dev,
 static ssize_t numa_node_show(struct device *dev, struct device_attribute *attr,
 			      char *buf)
 {
-	return sprintf(buf, "%d\n", dev->numa_node);
+	return sysfs_emit(buf, "%d\n", dev->numa_node);
 }
 static DEVICE_ATTR_RW(numa_node);
 #endif
@@ -348,7 +348,7 @@ static ssize_t dma_mask_bits_show(struct device *dev,
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 
-	return sprintf(buf, "%d\n", fls64(pdev->dma_mask));
+	return sysfs_emit(buf, "%d\n", fls64(pdev->dma_mask));
 }
 static DEVICE_ATTR_RO(dma_mask_bits);
 
@@ -356,7 +356,7 @@ static ssize_t consistent_dma_mask_bits_show(struct device *dev,
 					     struct device_attribute *attr,
 					     char *buf)
 {
-	return sprintf(buf, "%d\n", fls64(dev->coherent_dma_mask));
+	return sysfs_emit(buf, "%d\n", fls64(dev->coherent_dma_mask));
 }
 static DEVICE_ATTR_RO(consistent_dma_mask_bits);
 
@@ -366,7 +366,7 @@ static ssize_t msi_bus_show(struct device *dev, struct device_attribute *attr,
 	struct pci_dev *pdev = to_pci_dev(dev);
 	struct pci_bus *subordinate = pdev->subordinate;
 
-	return sprintf(buf, "%u\n", subordinate ?
+	return sysfs_emit(buf, "%u\n", subordinate ?
 			  !(subordinate->bus_flags & PCI_BUS_FLAGS_NO_MSI)
 			    : !pdev->no_msi);
 }
@@ -523,7 +523,7 @@ static ssize_t d3cold_allowed_show(struct device *dev,
 				   struct device_attribute *attr, char *buf)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	return sprintf(buf, "%u\n", pdev->d3cold_allowed);
+	return sysfs_emit(buf, "%u\n", pdev->d3cold_allowed);
 }
 static DEVICE_ATTR_RW(d3cold_allowed);
 #endif
@@ -537,7 +537,7 @@ static ssize_t devspec_show(struct device *dev,
 
 	if (np == NULL)
 		return 0;
-	return sprintf(buf, "%pOF", np);
+	return sysfs_emit(buf, "%pOF", np);
 }
 static DEVICE_ATTR_RO(devspec);
 #endif
@@ -583,7 +583,7 @@ static ssize_t driver_override_show(struct device *dev,
 	ssize_t len;
 
 	device_lock(dev);
-	len = scnprintf(buf, PAGE_SIZE, "%s\n", pdev->driver_override);
+	len = sysfs_emit(buf, "%s\n", pdev->driver_override);
 	device_unlock(dev);
 	return len;
 }
@@ -658,9 +658,9 @@ static ssize_t boot_vga_show(struct device *dev, struct device_attribute *attr,
 	struct pci_dev *vga_dev = vga_default_device();
 
 	if (vga_dev)
-		return sprintf(buf, "%u\n", (pdev == vga_dev));
+		return sysfs_emit(buf, "%u\n", (pdev == vga_dev));
 
-	return sprintf(buf, "%u\n",
+	return sysfs_emit(buf, "%u\n",
 			  !!(pdev->resource[PCI_ROM_RESOURCE].flags &
 			     IORESOURCE_ROM_SHADOW));
 }