[PATCH v5 1/5] PCI/sysfs: Use sysfs_emit() and sysfs_emit_at() in "show" functions

[PATCH v5 1/5] PCI/sysfs: Use sysfs_emit() and sysfs_emit_at() in "show" functions

[Krzysztof Wilczyński]

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

Related to:
  commit ad025f8e46f3 ("PCI/sysfs: Use sysfs_emit() and sysfs_emit_at() in "show" functions")

Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
---
Changes in v2:
  None.
Changes in v3:
  Added Logan Gunthorpe's "Reviewed-by".
Changes in v4:
  Separated and squashed all the trivial sysfs_emit()/sysfs_emit_at()
  changes into a single patch as per Bjorn Helgaas' request.
  Carried Logan Gunthorpe's "Reviewed-by" over.
Changes in v5:
  None.

 drivers/pci/hotplug/pci_hotplug_core.c |  8 +++---
 drivers/pci/hotplug/rpadlpar_sysfs.c   |  4 +--
 drivers/pci/hotplug/shpchp_sysfs.c     | 38 ++++++++++++++------------
 drivers/pci/iov.c                      | 12 ++++----
 drivers/pci/msi.c                      |  8 +++---
 drivers/pci/p2pdma.c                   |  7 ++---
 drivers/pci/pci-label.c                |  6 ++--
 drivers/pci/pci.c                      |  2 +-
 drivers/pci/pcie/aer.c                 | 20 ++++++++------
 drivers/pci/pcie/aspm.c                |  4 +--
 drivers/pci/slot.c                     | 18 ++++++------
 drivers/pci/switch/switchtec.c         | 18 ++++++------
 12 files changed, 75 insertions(+), 70 deletions(-)

diff --git a/drivers/pci/hotplug/pci_hotplug_core.c b/drivers/pci/hotplug/pci_hotplug_core.c
index 5ac31f683b85..058d5937d8a9 100644
--- a/drivers/pci/hotplug/pci_hotplug_core.c
+++ b/drivers/pci/hotplug/pci_hotplug_core.c
@@ -73,7 +73,7 @@ static ssize_t power_read_file(struct pci_slot *pci_slot, char *buf)
 	if (retval)
 		return retval;
 
-	return sprintf(buf, "%d\n", value);
+	return sysfs_emit(buf, "%d\n", value);
 }
 
 static ssize_t power_write_file(struct pci_slot *pci_slot, const char *buf,
@@ -130,7 +130,7 @@ static ssize_t attention_read_file(struct pci_slot *pci_slot, char *buf)
 	if (retval)
 		return retval;
 
-	return sprintf(buf, "%d\n", value);
+	return sysfs_emit(buf, "%d\n", value);
 }
 
 static ssize_t attention_write_file(struct pci_slot *pci_slot, const char *buf,
@@ -175,7 +175,7 @@ static ssize_t latch_read_file(struct pci_slot *pci_slot, char *buf)
 	if (retval)
 		return retval;
 
-	return sprintf(buf, "%d\n", value);
+	return sysfs_emit(buf, "%d\n", value);
 }
 
 static struct pci_slot_attribute hotplug_slot_attr_latch = {
@@ -192,7 +192,7 @@ static ssize_t presence_read_file(struct pci_slot *pci_slot, char *buf)
 	if (retval)
 		return retval;
 
-	return sprintf(buf, "%d\n", value);
+	return sysfs_emit(buf, "%d\n", value);
 }
 
 static struct pci_slot_attribute hotplug_slot_attr_presence = {
diff --git a/drivers/pci/hotplug/rpadlpar_sysfs.c b/drivers/pci/hotplug/rpadlpar_sysfs.c
index dbfa0b55d31a..068b7810a574 100644
--- a/drivers/pci/hotplug/rpadlpar_sysfs.c
+++ b/drivers/pci/hotplug/rpadlpar_sysfs.c
@@ -50,7 +50,7 @@ static ssize_t add_slot_store(struct kobject *kobj, struct kobj_attribute *attr,
 static ssize_t add_slot_show(struct kobject *kobj,
 			     struct kobj_attribute *attr, char *buf)
 {
-	return sprintf(buf, "0\n");
+	return sysfs_emit(buf, "0\n");
 }
 
 static ssize_t remove_slot_store(struct kobject *kobj,
@@ -80,7 +80,7 @@ static ssize_t remove_slot_store(struct kobject *kobj,
 static ssize_t remove_slot_show(struct kobject *kobj,
 				struct kobj_attribute *attr, char *buf)
 {
-	return sprintf(buf, "0\n");
+	return sysfs_emit(buf, "0\n");
 }
 
 static struct kobj_attribute add_slot_attr =
diff --git a/drivers/pci/hotplug/shpchp_sysfs.c b/drivers/pci/hotplug/shpchp_sysfs.c
index 45658bb5c554..64beed7a26be 100644
--- a/drivers/pci/hotplug/shpchp_sysfs.c
+++ b/drivers/pci/hotplug/shpchp_sysfs.c
@@ -24,50 +24,54 @@
 static ssize_t show_ctrl(struct device *dev, struct device_attribute *attr, char *buf)
 {
 	struct pci_dev *pdev;
-	char *out = buf;
 	int index, busnr;
 	struct resource *res;
 	struct pci_bus *bus;
+	size_t len = 0;
 
 	pdev = to_pci_dev(dev);
 	bus = pdev->subordinate;
 
-	out += sprintf(buf, "Free resources: memory\n");
+	len += sysfs_emit_at(buf, len, "Free resources: memory\n");
 	pci_bus_for_each_resource(bus, res, index) {
 		if (res && (res->flags & IORESOURCE_MEM) &&
 				!(res->flags & IORESOURCE_PREFETCH)) {
-			out += sprintf(out, "start = %8.8llx, length = %8.8llx\n",
-				       (unsigned long long)res->start,
-				       (unsigned long long)resource_size(res));
+			len += sysfs_emit_at(buf, len,
+					     "start = %8.8llx, length = %8.8llx\n",
+					     (unsigned long long)res->start,
+					     (unsigned long long)resource_size(res));
 		}
 	}
-	out += sprintf(out, "Free resources: prefetchable memory\n");
+	len += sysfs_emit_at(buf, len, "Free resources: prefetchable memory\n");
 	pci_bus_for_each_resource(bus, res, index) {
 		if (res && (res->flags & IORESOURCE_MEM) &&
 			       (res->flags & IORESOURCE_PREFETCH)) {
-			out += sprintf(out, "start = %8.8llx, length = %8.8llx\n",
-				       (unsigned long long)res->start,
-				       (unsigned long long)resource_size(res));
+			len += sysfs_emit_at(buf, len,
+					     "start = %8.8llx, length = %8.8llx\n",
+					     (unsigned long long)res->start,
+					     (unsigned long long)resource_size(res));
 		}
 	}
-	out += sprintf(out, "Free resources: IO\n");
+	len += sysfs_emit_at(buf, len, "Free resources: IO\n");
 	pci_bus_for_each_resource(bus, res, index) {
 		if (res && (res->flags & IORESOURCE_IO)) {
-			out += sprintf(out, "start = %8.8llx, length = %8.8llx\n",
-				       (unsigned long long)res->start,
-				       (unsigned long long)resource_size(res));
+			len += sysfs_emit_at(buf, len,
+					     "start = %8.8llx, length = %8.8llx\n",
+					     (unsigned long long)res->start,
+					     (unsigned long long)resource_size(res));
 		}
 	}
-	out += sprintf(out, "Free resources: bus numbers\n");
+	len += sysfs_emit_at(buf, len, "Free resources: bus numbers\n");
 	for (busnr = bus->busn_res.start; busnr <= bus->busn_res.end; busnr++) {
 		if (!pci_find_bus(pci_domain_nr(bus), busnr))
 			break;
 	}
 	if (busnr < bus->busn_res.end)
-		out += sprintf(out, "start = %8.8x, length = %8.8x\n",
-				busnr, (int)(bus->busn_res.end - busnr));
+		len += sysfs_emit_at(buf, len,
+				     "start = %8.8x, length = %8.8x\n",
+				     busnr, (int)(bus->busn_res.end - busnr));
 
-	return out - buf;
+	return len;
 }
 static DEVICE_ATTR(ctrl, S_IRUGO, show_ctrl, NULL);
 
diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index afc06e6ce115..a71258347323 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -346,7 +346,7 @@ static ssize_t sriov_totalvfs_show(struct device *dev,
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 
-	return sprintf(buf, "%u\n", pci_sriov_get_totalvfs(pdev));
+	return sysfs_emit(buf, "%u\n", pci_sriov_get_totalvfs(pdev));
 }
 
 static ssize_t sriov_numvfs_show(struct device *dev,
@@ -361,7 +361,7 @@ static ssize_t sriov_numvfs_show(struct device *dev,
 	num_vfs = pdev->sriov->num_VFs;
 	device_unlock(&pdev->dev);
 
-	return sprintf(buf, "%u\n", num_vfs);
+	return sysfs_emit(buf, "%u\n", num_vfs);
 }
 
 /*
@@ -435,7 +435,7 @@ static ssize_t sriov_offset_show(struct device *dev,
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 
-	return sprintf(buf, "%u\n", pdev->sriov->offset);
+	return sysfs_emit(buf, "%u\n", pdev->sriov->offset);
 }
 
 static ssize_t sriov_stride_show(struct device *dev,
@@ -444,7 +444,7 @@ static ssize_t sriov_stride_show(struct device *dev,
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 
-	return sprintf(buf, "%u\n", pdev->sriov->stride);
+	return sysfs_emit(buf, "%u\n", pdev->sriov->stride);
 }
 
 static ssize_t sriov_vf_device_show(struct device *dev,
@@ -453,7 +453,7 @@ static ssize_t sriov_vf_device_show(struct device *dev,
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 
-	return sprintf(buf, "%x\n", pdev->sriov->vf_device);
+	return sysfs_emit(buf, "%x\n", pdev->sriov->vf_device);
 }
 
 static ssize_t sriov_drivers_autoprobe_show(struct device *dev,
@@ -462,7 +462,7 @@ static ssize_t sriov_drivers_autoprobe_show(struct device *dev,
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 
-	return sprintf(buf, "%u\n", pdev->sriov->drivers_autoprobe);
+	return sysfs_emit(buf, "%u\n", pdev->sriov->drivers_autoprobe);
 }
 
 static ssize_t sriov_drivers_autoprobe_store(struct device *dev,
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 217dc9f0231f..9232255c8515 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -464,11 +464,11 @@ static ssize_t msi_mode_show(struct device *dev, struct device_attribute *attr,
 		return retval;
 
 	entry = irq_get_msi_desc(irq);
-	if (entry)
-		return sprintf(buf, "%s\n",
-				entry->msi_attrib.is_msix ? "msix" : "msi");
+	if (!entry)
+		return -ENODEV;
 
-	return -ENODEV;
+	return sysfs_emit(buf, "%s\n",
+			  entry->msi_attrib.is_msix ? "msix" : "msi");
 }
 
 static int populate_msi_sysfs(struct pci_dev *pdev)
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 196382630363..a1351b3e2c4c 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -53,7 +53,7 @@ static ssize_t size_show(struct device *dev, struct device_attribute *attr,
 	if (pdev->p2pdma->pool)
 		size = gen_pool_size(pdev->p2pdma->pool);
 
-	return scnprintf(buf, PAGE_SIZE, "%zd\n", size);
+	return sysfs_emit(buf, "%zd\n", size);
 }
 static DEVICE_ATTR_RO(size);
 
@@ -66,7 +66,7 @@ static ssize_t available_show(struct device *dev, struct device_attribute *attr,
 	if (pdev->p2pdma->pool)
 		avail = gen_pool_avail(pdev->p2pdma->pool);
 
-	return scnprintf(buf, PAGE_SIZE, "%zd\n", avail);
+	return sysfs_emit(buf, "%zd\n", avail);
 }
 static DEVICE_ATTR_RO(available);
 
@@ -75,8 +75,7 @@ static ssize_t published_show(struct device *dev, struct device_attribute *attr,
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 
-	return scnprintf(buf, PAGE_SIZE, "%d\n",
-			 pdev->p2pdma->p2pmem_published);
+	return sysfs_emit(buf, "%d\n", pdev->p2pdma->p2pmem_published);
 }
 static DEVICE_ATTR_RO(published);
 
diff --git a/drivers/pci/pci-label.c b/drivers/pci/pci-label.c
index c32f3b7540e8..311dd48e2881 100644
--- a/drivers/pci/pci-label.c
+++ b/drivers/pci/pci-label.c
@@ -175,11 +175,11 @@ static int dsm_get_label(struct device *dev, char *buf,
 		 * this entry must return a null string.
 		 */
 		if (attr == ACPI_ATTR_INDEX_SHOW) {
-			scnprintf(buf, PAGE_SIZE, "%llu\n", tmp->integer.value);
+			sysfs_emit(buf, "%llu\n", tmp->integer.value);
 		} else if (attr == ACPI_ATTR_LABEL_SHOW) {
 			if (tmp[1].type == ACPI_TYPE_STRING)
-				scnprintf(buf, PAGE_SIZE, "%s\n",
-					  tmp[1].string.pointer);
+				sysfs_emit(buf, "%s\n",
+					   tmp[1].string.pointer);
 			else if (tmp[1].type == ACPI_TYPE_BUFFER)
 				dsm_label_utf16s_to_utf8s(tmp + 1, buf);
 		}
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b717680377a9..5ed316ea5831 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6439,7 +6439,7 @@ static ssize_t resource_alignment_show(struct bus_type *bus, char *buf)
 
 	spin_lock(&resource_alignment_lock);
 	if (resource_alignment_param)
-		count = scnprintf(buf, PAGE_SIZE, "%s", resource_alignment_param);
+		count = sysfs_emit(buf, "%s", resource_alignment_param);
 	spin_unlock(&resource_alignment_lock);
 
 	/*
diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index ec943cee5ecc..40ef7bed7a77 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -529,21 +529,23 @@ static const char *aer_agent_string[] = {
 		     char *buf)						\
 {									\
 	unsigned int i;							\
-	char *str = buf;						\
 	struct pci_dev *pdev = to_pci_dev(dev);				\
 	u64 *stats = pdev->aer_stats->stats_array;			\
+	size_t len = 0;							\
 									\
 	for (i = 0; i < ARRAY_SIZE(strings_array); i++) {		\
 		if (strings_array[i])					\
-			str += sprintf(str, "%s %llu\n",		\
-				       strings_array[i], stats[i]);	\
+			len += sysfs_emit_at(buf, len, "%s %llu\n",	\
+					     strings_array[i],		\
+					     stats[i]);			\
 		else if (stats[i])					\
-			str += sprintf(str, #stats_array "_bit[%d] %llu\n",\
-				       i, stats[i]);			\
+			len += sysfs_emit_at(buf, len,			\
+					     #stats_array "_bit[%d] %llu\n",\
+					     i, stats[i]);		\
 	}								\
-	str += sprintf(str, "TOTAL_%s %llu\n", total_string,		\
-		       pdev->aer_stats->total_field);			\
-	return str-buf;							\
+	len += sysfs_emit_at(buf, len, "TOTAL_%s %llu\n", total_string,	\
+			     pdev->aer_stats->total_field);		\
+	return len;							\
 }									\
 static DEVICE_ATTR_RO(name)
 
@@ -563,7 +565,7 @@ aer_stats_dev_attr(aer_dev_nonfatal, dev_nonfatal_errs,
 		     char *buf)						\
 {									\
 	struct pci_dev *pdev = to_pci_dev(dev);				\
-	return sprintf(buf, "%llu\n", pdev->aer_stats->field);		\
+	return sysfs_emit(buf, "%llu\n", pdev->aer_stats->field);	\
 }									\
 static DEVICE_ATTR_RO(name)
 
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index ac0557a305af..013a47f587ce 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1208,7 +1208,7 @@ static ssize_t aspm_attr_show_common(struct device *dev,
 	struct pci_dev *pdev = to_pci_dev(dev);
 	struct pcie_link_state *link = pcie_aspm_get_link(pdev);
 
-	return sprintf(buf, "%d\n", (link->aspm_enabled & state) ? 1 : 0);
+	return sysfs_emit(buf, "%d\n", (link->aspm_enabled & state) ? 1 : 0);
 }
 
 static ssize_t aspm_attr_store_common(struct device *dev,
@@ -1265,7 +1265,7 @@ static ssize_t clkpm_show(struct device *dev,
 	struct pci_dev *pdev = to_pci_dev(dev);
 	struct pcie_link_state *link = pcie_aspm_get_link(pdev);
 
-	return sprintf(buf, "%d\n", link->clkpm_enabled);
+	return sysfs_emit(buf, "%d\n", link->clkpm_enabled);
 }
 
 static ssize_t clkpm_store(struct device *dev,
diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
index d627dd9179b4..751a26668e3a 100644
--- a/drivers/pci/slot.c
+++ b/drivers/pci/slot.c
@@ -39,19 +39,19 @@ static const struct sysfs_ops pci_slot_sysfs_ops = {
 static ssize_t address_read_file(struct pci_slot *slot, char *buf)
 {
 	if (slot->number == 0xff)
-		return sprintf(buf, "%04x:%02x\n",
-				pci_domain_nr(slot->bus),
-				slot->bus->number);
-	else
-		return sprintf(buf, "%04x:%02x:%02x\n",
-				pci_domain_nr(slot->bus),
-				slot->bus->number,
-				slot->number);
+		return sysfs_emit(buf, "%04x:%02x\n",
+				  pci_domain_nr(slot->bus),
+				  slot->bus->number);
+
+	return sysfs_emit(buf, "%04x:%02x:%02x\n",
+			  pci_domain_nr(slot->bus),
+			  slot->bus->number,
+			  slot->number);
 }
 
 static ssize_t bus_speed_read(enum pci_bus_speed speed, char *buf)
 {
-	return sprintf(buf, "%s\n", pci_speed_string(speed));
+	return sysfs_emit(buf, "%s\n", pci_speed_string(speed));
 }
 
 static ssize_t max_speed_read_file(struct pci_slot *slot, char *buf)
diff --git a/drivers/pci/switch/switchtec.c b/drivers/pci/switch/switchtec.c
index ba52459928f7..0b301f8be9ed 100644
--- a/drivers/pci/switch/switchtec.c
+++ b/drivers/pci/switch/switchtec.c
@@ -280,7 +280,7 @@ static ssize_t device_version_show(struct device *dev,
 
 	ver = ioread32(&stdev->mmio_sys_info->device_version);
 
-	return sprintf(buf, "%x\n", ver);
+	return sysfs_emit(buf, "%x\n", ver);
 }
 static DEVICE_ATTR_RO(device_version);
 
@@ -292,7 +292,7 @@ static ssize_t fw_version_show(struct device *dev,
 
 	ver = ioread32(&stdev->mmio_sys_info->firmware_version);
 
-	return sprintf(buf, "%08x\n", ver);
+	return sysfs_emit(buf, "%08x\n", ver);
 }
 static DEVICE_ATTR_RO(fw_version);
 
@@ -344,7 +344,7 @@ static ssize_t component_vendor_show(struct device *dev,
 
 	/* component_vendor field not supported after gen3 */
 	if (stdev->gen != SWITCHTEC_GEN3)
-		return sprintf(buf, "none\n");
+		return sysfs_emit(buf, "none\n");
 
 	return io_string_show(buf, &si->gen3.component_vendor,
 			      sizeof(si->gen3.component_vendor));
@@ -359,9 +359,9 @@ static ssize_t component_id_show(struct device *dev,
 
 	/* component_id field not supported after gen3 */
 	if (stdev->gen != SWITCHTEC_GEN3)
-		return sprintf(buf, "none\n");
+		return sysfs_emit(buf, "none\n");
 
-	return sprintf(buf, "PM%04X\n", id);
+	return sysfs_emit(buf, "PM%04X\n", id);
 }
 static DEVICE_ATTR_RO(component_id);
 
@@ -373,9 +373,9 @@ static ssize_t component_revision_show(struct device *dev,
 
 	/* component_revision field not supported after gen3 */
 	if (stdev->gen != SWITCHTEC_GEN3)
-		return sprintf(buf, "255\n");
+		return sysfs_emit(buf, "255\n");
 
-	return sprintf(buf, "%d\n", rev);
+	return sysfs_emit(buf, "%d\n", rev);
 }
 static DEVICE_ATTR_RO(component_revision);
 
@@ -384,7 +384,7 @@ static ssize_t partition_show(struct device *dev,
 {
 	struct switchtec_dev *stdev = to_stdev(dev);
 
-	return sprintf(buf, "%d\n", stdev->partition);
+	return sysfs_emit(buf, "%d\n", stdev->partition);
 }
 static DEVICE_ATTR_RO(partition);
 
@@ -393,7 +393,7 @@ static ssize_t partition_count_show(struct device *dev,
 {
 	struct switchtec_dev *stdev = to_stdev(dev);
 
-	return sprintf(buf, "%d\n", stdev->partition_count);
+	return sysfs_emit(buf, "%d\n", stdev->partition_count);
 }
 static DEVICE_ATTR_RO(partition_count);
 
-- 
2.31.1

[PATCH v5 2/5] PCI/sysfs: Use return value from dsm_label_utf16s_to_utf8s() directly

[Krzysztof Wilczyński]

Modify the function dsm_label_utf16s_to_utf8s() to directly return the
number of bytes written into the buffer so that the strlen() used later
to calculate the length of the buffer can be removed as it would no
longer be needed.

No functional change intended.

Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
---
Changes in v2:
  None.
Changes in v3:
  None.
Changes in v4:
  Separated this patch from other trivial sysfs_emit()/sysfs_emit_at()
  patches into a separate patch as per Bjorn Helgaas' request.
  Added Logan Gunthorpe's "Reviewed-by".
Changes in v5:
  None.

 drivers/pci/pci-label.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/pci-label.c b/drivers/pci/pci-label.c
index 311dd48e2881..000e169c7197 100644
--- a/drivers/pci/pci-label.c
+++ b/drivers/pci/pci-label.c
@@ -139,14 +139,17 @@ enum acpi_attr_enum {
 	ACPI_ATTR_INDEX_SHOW,
 };
 
-static void dsm_label_utf16s_to_utf8s(union acpi_object *obj, char *buf)
+static int dsm_label_utf16s_to_utf8s(union acpi_object *obj, char *buf)
 {
 	int len;
+
 	len = utf16s_to_utf8s((const wchar_t *)obj->buffer.pointer,
 			      obj->buffer.length,
 			      UTF16_LITTLE_ENDIAN,
 			      buf, PAGE_SIZE);
 	buf[len] = '\n';
+
+	return len;
 }
 
 static int dsm_get_label(struct device *dev, char *buf,
@@ -154,7 +157,7 @@ static int dsm_get_label(struct device *dev, char *buf,
 {
 	acpi_handle handle = ACPI_HANDLE(dev);
 	union acpi_object *obj, *tmp;
-	int len = -1;
+	int len = 0;
 
 	if (!handle)
 		return -1;
@@ -175,20 +178,19 @@ static int dsm_get_label(struct device *dev, char *buf,
 		 * this entry must return a null string.
 		 */
 		if (attr == ACPI_ATTR_INDEX_SHOW) {
-			sysfs_emit(buf, "%llu\n", tmp->integer.value);
+			len = sysfs_emit(buf, "%llu\n", tmp->integer.value);
 		} else if (attr == ACPI_ATTR_LABEL_SHOW) {
 			if (tmp[1].type == ACPI_TYPE_STRING)
-				sysfs_emit(buf, "%s\n",
-					   tmp[1].string.pointer);
+				len = sysfs_emit(buf, "%s\n",
+						 tmp[1].string.pointer);
 			else if (tmp[1].type == ACPI_TYPE_BUFFER)
-				dsm_label_utf16s_to_utf8s(tmp + 1, buf);
+				len = dsm_label_utf16s_to_utf8s(tmp + 1, buf);
 		}
-		len = strlen(buf) > 0 ? strlen(buf) : -1;
 	}
 
 	ACPI_FREE(obj);
 
-	return len;
+	return len > 0 ? len : -1;
 }
 
 static ssize_t label_show(struct device *dev, struct device_attribute *attr,
-- 
2.31.1

Re: [PATCH v5 2/5] PCI/sysfs: Use return value from dsm_label_utf16s_to_utf8s() directly

[Joe Perches]

On Thu, 2021-05-27 at 20:16 +0000, Krzysztof Wilczyński wrote:
> Modify the function dsm_label_utf16s_to_utf8s() to directly return the
> number of bytes written into the buffer so that the strlen() used later
> to calculate the length of the buffer can be removed as it would no
> longer be needed.
[]
> diff --git a/drivers/pci/pci-label.c b/drivers/pci/pci-label.c
[]
> @@ -139,14 +139,17 @@ enum acpi_attr_enum {
>  	ACPI_ATTR_INDEX_SHOW,
>  };
>  
> 
> -static void dsm_label_utf16s_to_utf8s(union acpi_object *obj, char *buf)
> +static int dsm_label_utf16s_to_utf8s(union acpi_object *obj, char *buf)
>  {
>  	int len;
> +
>  	len = utf16s_to_utf8s((const wchar_t *)obj->buffer.pointer,
>  			      obj->buffer.length,
>  			      UTF16_LITTLE_ENDIAN,
>  			      buf, PAGE_SIZE);

This should be PAGE_SIZE - 1 no?

>  	buf[len] = '\n';
> +
> +	return len;

return len + 1 ?

Re: [PATCH v5 2/5] PCI/sysfs: Use return value from dsm_label_utf16s_to_utf8s() directly

[Krzysztof Wilczyński]

Hi Joe,

[...]
> > -static void dsm_label_utf16s_to_utf8s(union acpi_object *obj, char *buf)
> > +static int dsm_label_utf16s_to_utf8s(union acpi_object *obj, char *buf)
> >  {
> >  	int len;
> > +
> >  	len = utf16s_to_utf8s((const wchar_t *)obj->buffer.pointer,
> >  			      obj->buffer.length,
> >  			      UTF16_LITTLE_ENDIAN,
> >  			      buf, PAGE_SIZE);
> 
> This should be PAGE_SIZE - 1 no?
> 
> >  	buf[len] = '\n';
> > +
> > +	return len;
> 
> return len + 1 ?

Good catch!

I left the original code as-is, and this old latent bug would remain
there.  I am glad you had a moment to review this new version.  Thank
you!

I will send v6 later and include this as separate patch per Bjorn's
request.

	Krzysztof

[PATCH v5 3/5] PCI/sysfs: Fix trailing newline handling of resource_alignment_param

[Krzysztof Wilczyński]

The value of the "resource_alignment" can be specified using a kernel
command-line argument (using the "pci=resource_alignment=") or through
the corresponding sysfs object under the /sys/bus/pci path.

Currently, when the value is set via the kernel command-line argument,
and then subsequently accessed through sysfs object, the value read back
will not be correct, as per:

  # grep -oE 'pci=resource_alignment.+' /proc/cmdline
  pci=resource_alignment=20@00:1f.2
  # cat /sys/bus/pci/resource_alignment
  20@00:1f.

This is also true when the value is set through the sysfs object, but
the trailing newline has not been included, as per:

  # echo -n 20@00:1f.2 > /sys/bus/pci/resource_alignment
  # cat /sys/bus/pci/resource_alignment
  20@00:1f.

When the value set through the sysfs object includes the trailing
newline, then reading it back will work as intended, as per:

  # echo 20@00:1f.2 > /sys/bus/pci/resource_alignment
  # cat /sys/bus/pci/resource_alignment
  20@00:1f.2

To fix this inconsistency, append a trailing newline in the show()
function and strip the trailing line in the store() function if one is
present.

Also, allow for the value previously set using either a command-line
argument or through the sysfs object to be cleared at run-time.

Fixes: e499081da1a2 ("PCI: Force trailing new line to resource_alignment_param in sysfs")
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
---
Changes in v2:
  None.
Changes in v3:
  Added Logan Gunthorpe's "Reviewed-by".
Changes in v4:
  None.
Changes in v5:
  Added check to ensure that there is an extra space left in the buffer
  for the newline character, assuming that it might be provided.

 drivers/pci/pci.c | 34 ++++++++++++++++++++--------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 5ed316ea5831..b46445a49543 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6439,34 +6439,40 @@ static ssize_t resource_alignment_show(struct bus_type *bus, char *buf)
 
 	spin_lock(&resource_alignment_lock);
 	if (resource_alignment_param)
-		count = sysfs_emit(buf, "%s", resource_alignment_param);
+		count = sysfs_emit(buf, "%s\n", resource_alignment_param);
 	spin_unlock(&resource_alignment_lock);
 
-	/*
-	 * When set by the command line, resource_alignment_param will not
-	 * have a trailing line feed, which is ugly. So conditionally add
-	 * it here.
-	 */
-	if (count >= 2 && buf[count - 2] != '\n' && count < PAGE_SIZE - 1) {
-		buf[count - 1] = '\n';
-		buf[count++] = 0;
-	}
-
 	return count;
 }
 
 static ssize_t resource_alignment_store(struct bus_type *bus,
 					const char *buf, size_t count)
 {
-	char *param = kstrndup(buf, count, GFP_KERNEL);
+	char *param, *old, *end;
+
+	if (count >= (PAGE_SIZE - 1))
+		return -EINVAL;
 
+	param = kstrndup(buf, count, GFP_KERNEL);
 	if (!param)
 		return -ENOMEM;
 
+	end = strchr(param, '\n');
+	if (end)
+		*end = '\0';
+
 	spin_lock(&resource_alignment_lock);
-	kfree(resource_alignment_param);
-	resource_alignment_param = param;
+	old = resource_alignment_param;
+	if (strlen(param)) {
+		resource_alignment_param = param;
+	} else {
+		kfree(resource_alignment_param);
+		resource_alignment_param = NULL;
+	}
 	spin_unlock(&resource_alignment_lock);
+
+	kfree(old);
+
 	return count;
 }
 
-- 
2.31.1

[PATCH v5 4/5] PCI/sysfs: Add missing trailing newline to devspec_show()

[Krzysztof Wilczyński]

At the moment, when the value of the "devspec" sysfs object is read from
the user space there will be no newline present, and the utilities such
as the "cat" command won't display the result of the read correctly in
a shell, as the trailing newline is currently missing.

To fix this, append a newline character in the show() function.

Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
---
Changes in v2:
  None.
Changes in v3:
  Added Logan Gunthorpe's "Reviewed-by".
Changes in v4:
  None.
Changes in v5:
  None.

 drivers/pci/pci-sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index beb8d1f4fafe..5d63df7c1820 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -537,7 +537,7 @@ static ssize_t devspec_show(struct device *dev,
 
 	if (np == NULL)
 		return 0;
-	return sysfs_emit(buf, "%pOF", np);
+	return sysfs_emit(buf, "%pOF\n", np);
 }
 static DEVICE_ATTR_RO(devspec);
 #endif
-- 
2.31.1

[PATCH v5 5/5] PCI/sysfs: Only show value when driver_override is not NULL

[Krzysztof Wilczyński]

Only expose the value of the "driver_override" variable through the
corresponding sysfs object when a value is actually set.

Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
---
Changes in v2:
  None.
Changes in v3:
  Added Logan Gunthorpe's "Reviewed-by".
Changes in v4:
  None.
Changes in v5:
  None.

 drivers/pci/pci-sysfs.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 5d63df7c1820..4e9f582ca10f 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -580,10 +580,11 @@ static ssize_t driver_override_show(struct device *dev,
 				    struct device_attribute *attr, char *buf)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	ssize_t len;
+	ssize_t len = 0;
 
 	device_lock(dev);
-	len = sysfs_emit(buf, "%s\n", pdev->driver_override);
+	if (pdev->driver_override)
+		len = sysfs_emit(buf, "%s\n", pdev->driver_override);
 	device_unlock(dev);
 	return len;
 }
-- 
2.31.1