[PATCH 0/2] Deduplicate bin_attribute simple read() callbacks

[PATCH 0/2] Deduplicate bin_attribute simple read() callbacks

[Lukas Wunner]

For my upcoming PCI device authentication v2 patches, I have the need
to expose a simple buffer in virtual memory as a bin_attribute.

It turns out we've duplicated the ->read() callback for such simple
buffers a fair number of times across the tree.

So instead of reinventing the wheel, I decided to introduce a common
helper and eliminate all duplications I could find.

I'm open to a bikeshedding discussion on the sysfs_bin_attr_simple_read()
name. ;)

Lukas Wunner (2):
  sysfs: Add sysfs_bin_attr_simple_read() helper
  treewide: Use sysfs_bin_attr_simple_read() helper

 arch/powerpc/platforms/powernv/opal.c              | 10 +-------
 drivers/acpi/bgrt.c                                |  9 +-------
 drivers/firmware/dmi_scan.c                        | 12 ++--------
 drivers/firmware/efi/rci2-table.c                  | 10 +-------
 drivers/gpu/drm/i915/gvt/firmware.c                | 26 +++++----------------
 .../intel/int340x_thermal/int3400_thermal.c        |  9 +-------
 fs/sysfs/file.c                                    | 27 ++++++++++++++++++++++
 include/linux/sysfs.h                              | 15 ++++++++++++
 init/initramfs.c                                   | 10 +-------
 kernel/module/sysfs.c                              | 13 +----------
 10 files changed, 56 insertions(+), 85 deletions(-)

-- 
2.43.0

[PATCH 1/2] sysfs: Add sysfs_bin_attr_simple_read() helper

[Lukas Wunner]

When drivers expose a bin_attribute in sysfs which is backed by a buffer
in memory, a common pattern is to set the @private and @size members in
struct bin_attribute to the buffer's location and size.

The ->read() callback then merely consists of a single memcpy() call.
It's not even necessary to perform bounds checks as these are already
handled by sysfs_kf_bin_read().

However each driver is so far providing its own ->read() implementation.
The pattern is sufficiently frequent to merit a public helper, so add
sysfs_bin_attr_simple_read() as well as BIN_ATTR_SIMPLE_RO() and
BIN_ATTR_SIMPLE_ADMIN_RO() macros to ease declaration of such
bin_attributes and reduce LoC and .text section size.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
---
 fs/sysfs/file.c       | 27 +++++++++++++++++++++++++++
 include/linux/sysfs.h | 15 +++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 6b7652f..289b57d 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -783,3 +783,30 @@ int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
 	return len;
 }
 EXPORT_SYMBOL_GPL(sysfs_emit_at);
+
+/**
+ *	sysfs_bin_attr_simple_read - read callback to simply copy from memory.
+ *	@file:	attribute file which is being read.
+ *	@kobj:	object to which the attribute belongs.
+ *	@attr:	attribute descriptor.
+ *	@buf:	destination buffer.
+ *	@off:	offset in bytes from which to read.
+ *	@count:	maximum number of bytes to read.
+ *
+ * Simple ->read() callback for bin_attributes backed by a buffer in memory.
+ * The @private and @size members in struct bin_attribute must be set to the
+ * buffer's location and size before the bin_attribute is created in sysfs.
+ *
+ * Bounds check for @off and @count is done in sysfs_kf_bin_read().
+ * Negative value check for @off is done in vfs_setpos() and default_llseek().
+ *
+ * Returns number of bytes written to @buf.
+ */
+ssize_t sysfs_bin_attr_simple_read(struct file *file, struct kobject *kobj,
+				   struct bin_attribute *attr, char *buf,
+				   loff_t off, size_t count)
+{
+	memcpy(buf, attr->private + off, count);
+	return count;
+}
+EXPORT_SYMBOL_GPL(sysfs_bin_attr_simple_read);
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 326341c..a7d725f 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -371,6 +371,17 @@ struct bin_attribute bin_attr_##_name = __BIN_ATTR_ADMIN_RO(_name, _size)
 #define BIN_ATTR_ADMIN_RW(_name, _size)					\
 struct bin_attribute bin_attr_##_name = __BIN_ATTR_ADMIN_RW(_name, _size)
 
+#define __BIN_ATTR_SIMPLE_RO(_name, _mode) {				\
+	.attr	= { .name = __stringify(_name), .mode = _mode },	\
+	.read	= sysfs_bin_attr_simple_read,				\
+}
+
+#define BIN_ATTR_SIMPLE_RO(_name)					\
+struct bin_attribute bin_attr_##_name = __BIN_ATTR_SIMPLE_RO(_name, 0444)
+
+#define BIN_ATTR_SIMPLE_ADMIN_RO(_name)					\
+struct bin_attribute bin_attr_##_name = __BIN_ATTR_SIMPLE_RO(_name, 0400)
+
 struct sysfs_ops {
 	ssize_t	(*show)(struct kobject *, struct attribute *, char *);
 	ssize_t	(*store)(struct kobject *, struct attribute *, const char *, size_t);
@@ -478,6 +489,10 @@ int sysfs_group_change_owner(struct kobject *kobj,
 __printf(3, 4)
 int sysfs_emit_at(char *buf, int at, const char *fmt, ...);
 
+ssize_t sysfs_bin_attr_simple_read(struct file *file, struct kobject *kobj,
+				   struct bin_attribute *attr, char *buf,
+				   loff_t off, size_t count);
+
 #else /* CONFIG_SYSFS */
 
 static inline int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
-- 
2.43.0

[PATCH 2/2] treewide: Use sysfs_bin_attr_simple_read() helper

[Lukas Wunner]

Deduplicate ->read() callbacks of bin_attributes which are backed by a
simple buffer in memory:

Use the newly introduced sysfs_bin_attr_simple_read() helper instead,
either by referencing it directly or by declaring such bin_attributes
with BIN_ATTR_SIMPLE_RO() or BIN_ATTR_SIMPLE_ADMIN_RO().

Aside from a reduction of LoC, this shaves off a few bytes from vmlinux
(304 bytes on an x86_64 allyesconfig).

No functional change intended.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
---
 arch/powerpc/platforms/powernv/opal.c              | 10 +--------
 drivers/acpi/bgrt.c                                |  9 +-------
 drivers/firmware/dmi_scan.c                        | 12 ++--------
 drivers/firmware/efi/rci2-table.c                  | 10 +--------
 drivers/gpu/drm/i915/gvt/firmware.c                | 26 +++++-----------------
 .../intel/int340x_thermal/int3400_thermal.c        |  9 +-------
 init/initramfs.c                                   | 10 +--------
 kernel/module/sysfs.c                              | 13 +----------
 8 files changed, 14 insertions(+), 85 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 45dd77e..5d0f35b 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -792,14 +792,6 @@ static int __init opal_sysfs_init(void)
 	return 0;
 }
 
-static ssize_t export_attr_read(struct file *fp, struct kobject *kobj,
-				struct bin_attribute *bin_attr, char *buf,
-				loff_t off, size_t count)
-{
-	return memory_read_from_buffer(buf, count, &off, bin_attr->private,
-				       bin_attr->size);
-}
-
 static int opal_add_one_export(struct kobject *parent, const char *export_name,
 			       struct device_node *np, const char *prop_name)
 {
@@ -826,7 +818,7 @@ static int opal_add_one_export(struct kobject *parent, const char *export_name,
 	sysfs_bin_attr_init(attr);
 	attr->attr.name = name;
 	attr->attr.mode = 0400;
-	attr->read = export_attr_read;
+	attr->read = sysfs_bin_attr_simple_read;
 	attr->private = __va(vals[0]);
 	attr->size = vals[1];
 
diff --git a/drivers/acpi/bgrt.c b/drivers/acpi/bgrt.c
index e4fb9e2..d1d9c92 100644
--- a/drivers/acpi/bgrt.c
+++ b/drivers/acpi/bgrt.c
@@ -29,14 +29,7 @@
 BGRT_SHOW(xoffset, image_offset_x);
 BGRT_SHOW(yoffset, image_offset_y);
 
-static ssize_t image_read(struct file *file, struct kobject *kobj,
-	       struct bin_attribute *attr, char *buf, loff_t off, size_t count)
-{
-	memcpy(buf, attr->private + off, count);
-	return count;
-}
-
-static BIN_ATTR_RO(image, 0);	/* size gets filled in later */
+static BIN_ATTR_SIMPLE_RO(image);
 
 static struct attribute *bgrt_attributes[] = {
 	&bgrt_attr_version.attr,
diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 015c95a..3d0f773 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -746,16 +746,8 @@ static void __init dmi_scan_machine(void)
 	pr_info("DMI not present or invalid.\n");
 }
 
-static ssize_t raw_table_read(struct file *file, struct kobject *kobj,
-			      struct bin_attribute *attr, char *buf,
-			      loff_t pos, size_t count)
-{
-	memcpy(buf, attr->private + pos, count);
-	return count;
-}
-
-static BIN_ATTR(smbios_entry_point, S_IRUSR, raw_table_read, NULL, 0);
-static BIN_ATTR(DMI, S_IRUSR, raw_table_read, NULL, 0);
+static BIN_ATTR_SIMPLE_ADMIN_RO(smbios_entry_point);
+static BIN_ATTR_SIMPLE_ADMIN_RO(DMI);
 
 static int __init dmi_init(void)
 {
diff --git a/drivers/firmware/efi/rci2-table.c b/drivers/firmware/efi/rci2-table.c
index de1a9a1..4fd45d6 100644
--- a/drivers/firmware/efi/rci2-table.c
+++ b/drivers/firmware/efi/rci2-table.c
@@ -40,15 +40,7 @@ struct rci2_table_global_hdr {
 static u32 rci2_table_len;
 unsigned long rci2_table_phys __ro_after_init = EFI_INVALID_TABLE_ADDR;
 
-static ssize_t raw_table_read(struct file *file, struct kobject *kobj,
-			      struct bin_attribute *attr, char *buf,
-			      loff_t pos, size_t count)
-{
-	memcpy(buf, attr->private + pos, count);
-	return count;
-}
-
-static BIN_ATTR(rci2, S_IRUSR, raw_table_read, NULL, 0);
+static BIN_ATTR_SIMPLE_ADMIN_RO(rci2);
 
 static u16 checksum(void)
 {
diff --git a/drivers/gpu/drm/i915/gvt/firmware.c b/drivers/gpu/drm/i915/gvt/firmware.c
index 4dd52ac..5e66a26 100644
--- a/drivers/gpu/drm/i915/gvt/firmware.c
+++ b/drivers/gpu/drm/i915/gvt/firmware.c
@@ -50,21 +50,7 @@ struct gvt_firmware_header {
 
 #define dev_to_drm_minor(d) dev_get_drvdata((d))
 
-static ssize_t
-gvt_firmware_read(struct file *filp, struct kobject *kobj,
-	     struct bin_attribute *attr, char *buf,
-	     loff_t offset, size_t count)
-{
-	memcpy(buf, attr->private + offset, count);
-	return count;
-}
-
-static struct bin_attribute firmware_attr = {
-	.attr = {.name = "gvt_firmware", .mode = (S_IRUSR)},
-	.read = gvt_firmware_read,
-	.write = NULL,
-	.mmap = NULL,
-};
+static BIN_ATTR_SIMPLE_ADMIN_RO(gvt_firmware);
 
 static int expose_firmware_sysfs(struct intel_gvt *gvt)
 {
@@ -107,10 +93,10 @@ static int expose_firmware_sysfs(struct intel_gvt *gvt)
 	crc32_start = offsetof(struct gvt_firmware_header, version);
 	h->crc32 = crc32_le(0, firmware + crc32_start, size - crc32_start);
 
-	firmware_attr.size = size;
-	firmware_attr.private = firmware;
+	bin_attr_gvt_firmware.size = size;
+	bin_attr_gvt_firmware.private = firmware;
 
-	ret = device_create_bin_file(&pdev->dev, &firmware_attr);
+	ret = device_create_bin_file(&pdev->dev, &bin_attr_gvt_firmware);
 	if (ret) {
 		vfree(firmware);
 		return ret;
@@ -122,8 +108,8 @@ static void clean_firmware_sysfs(struct intel_gvt *gvt)
 {
 	struct pci_dev *pdev = to_pci_dev(gvt->gt->i915->drm.dev);
 
-	device_remove_bin_file(&pdev->dev, &firmware_attr);
-	vfree(firmware_attr.private);
+	device_remove_bin_file(&pdev->dev, &bin_attr_gvt_firmware);
+	vfree(bin_attr_gvt_firmware.private);
 }
 
 /**
diff --git a/drivers/thermal/intel/int340x_thermal/int3400_thermal.c b/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
index 427d370..6d4b51a 100644
--- a/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
+++ b/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
@@ -73,14 +73,7 @@ struct odvp_attr {
 	struct device_attribute attr;
 };
 
-static ssize_t data_vault_read(struct file *file, struct kobject *kobj,
-	     struct bin_attribute *attr, char *buf, loff_t off, size_t count)
-{
-	memcpy(buf, attr->private + off, count);
-	return count;
-}
-
-static BIN_ATTR_RO(data_vault, 0);
+static BIN_ATTR_SIMPLE_RO(data_vault);
 
 static struct bin_attribute *data_attributes[] = {
 	&bin_attr_data_vault,
diff --git a/init/initramfs.c b/init/initramfs.c
index da79760..5193fae 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -575,15 +575,7 @@ static int __init initramfs_async_setup(char *str)
 #include <linux/initrd.h>
 #include <linux/kexec.h>
 
-static ssize_t raw_read(struct file *file, struct kobject *kobj,
-			struct bin_attribute *attr, char *buf,
-			loff_t pos, size_t count)
-{
-	memcpy(buf, attr->private + pos, count);
-	return count;
-}
-
-static BIN_ATTR(initrd, 0440, raw_read, NULL, 0);
+static BIN_ATTR(initrd, 0440, sysfs_bin_attr_simple_read, NULL, 0);
 
 void __init reserve_initrd_mem(void)
 {
diff --git a/kernel/module/sysfs.c b/kernel/module/sysfs.c
index d964167..26efe13 100644
--- a/kernel/module/sysfs.c
+++ b/kernel/module/sysfs.c
@@ -146,17 +146,6 @@ struct module_notes_attrs {
 	struct bin_attribute attrs[] __counted_by(notes);
 };
 
-static ssize_t module_notes_read(struct file *filp, struct kobject *kobj,
-				 struct bin_attribute *bin_attr,
-				 char *buf, loff_t pos, size_t count)
-{
-	/*
-	 * The caller checked the pos and count against our size.
-	 */
-	memcpy(buf, bin_attr->private + pos, count);
-	return count;
-}
-
 static void free_notes_attrs(struct module_notes_attrs *notes_attrs,
 			     unsigned int i)
 {
@@ -205,7 +194,7 @@ static void add_notes_attrs(struct module *mod, const struct load_info *info)
 			nattr->attr.mode = 0444;
 			nattr->size = info->sechdrs[i].sh_size;
 			nattr->private = (void *)info->sechdrs[i].sh_addr;
-			nattr->read = module_notes_read;
+			nattr->read = sysfs_bin_attr_simple_read;
 			++nattr;
 		}
 		++loaded;
-- 
2.43.0

Re: [PATCH 0/2] Deduplicate bin_attribute simple read() callbacks

[Ard Biesheuvel]

On Sat, 6 Apr 2024 at 15:52, Lukas Wunner <lukas@wunner.de> wrote:
>
> For my upcoming PCI device authentication v2 patches, I have the need
> to expose a simple buffer in virtual memory as a bin_attribute.
>
> It turns out we've duplicated the ->read() callback for such simple
> buffers a fair number of times across the tree.
>
> So instead of reinventing the wheel, I decided to introduce a common
> helper and eliminate all duplications I could find.
>
> I'm open to a bikeshedding discussion on the sysfs_bin_attr_simple_read()
> name. ;)
>
> Lukas Wunner (2):
>   sysfs: Add sysfs_bin_attr_simple_read() helper
>   treewide: Use sysfs_bin_attr_simple_read() helper
>

Acked-by: Ard Biesheuvel <ardb@kernel.org>

>  arch/powerpc/platforms/powernv/opal.c              | 10 +-------
>  drivers/acpi/bgrt.c                                |  9 +-------
>  drivers/firmware/dmi_scan.c                        | 12 ++--------
>  drivers/firmware/efi/rci2-table.c                  | 10 +-------
>  drivers/gpu/drm/i915/gvt/firmware.c                | 26 +++++----------------
>  .../intel/int340x_thermal/int3400_thermal.c        |  9 +-------
>  fs/sysfs/file.c                                    | 27 ++++++++++++++++++++++
>  include/linux/sysfs.h                              | 15 ++++++++++++
>  init/initramfs.c                                   | 10 +-------
>  kernel/module/sysfs.c                              | 13 +----------
>  10 files changed, 56 insertions(+), 85 deletions(-)
>
> --
> 2.43.0
>

Re: [PATCH 2/2] treewide: Use sysfs_bin_attr_simple_read() helper

[Zhi Wang]

On Sat, 6 Apr 2024 15:52:02 +0200
Lukas Wunner <lukas@wunner.de> wrote:

> Deduplicate ->read() callbacks of bin_attributes which are backed by a
> simple buffer in memory:
> 
> Use the newly introduced sysfs_bin_attr_simple_read() helper instead,
> either by referencing it directly or by declaring such bin_attributes
> with BIN_ATTR_SIMPLE_RO() or BIN_ATTR_SIMPLE_ADMIN_RO().
> 
> Aside from a reduction of LoC, this shaves off a few bytes from
> vmlinux (304 bytes on an x86_64 allyesconfig).
> 
> No functional change intended.
> 

As for GVT, looks good to me.

Acked-by: Zhi Wang <zhiwang@kernel.org>

> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> ---
>  arch/powerpc/platforms/powernv/opal.c              | 10 +--------
>  drivers/acpi/bgrt.c                                |  9 +-------
>  drivers/firmware/dmi_scan.c                        | 12 ++--------
>  drivers/firmware/efi/rci2-table.c                  | 10 +--------
>  drivers/gpu/drm/i915/gvt/firmware.c                | 26
> +++++----------------- .../intel/int340x_thermal/int3400_thermal.c
>     |  9 +------- init/initramfs.c
> | 10 +-------- kernel/module/sysfs.c                              |
> 13 +---------- 8 files changed, 14 insertions(+), 85 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/opal.c
> b/arch/powerpc/platforms/powernv/opal.c index 45dd77e..5d0f35b 100644
> --- a/arch/powerpc/platforms/powernv/opal.c
> +++ b/arch/powerpc/platforms/powernv/opal.c
> @@ -792,14 +792,6 @@ static int __init opal_sysfs_init(void)
>  	return 0;
>  }
>  
> -static ssize_t export_attr_read(struct file *fp, struct kobject
> *kobj,
> -				struct bin_attribute *bin_attr, char
> *buf,
> -				loff_t off, size_t count)
> -{
> -	return memory_read_from_buffer(buf, count, &off,
> bin_attr->private,
> -				       bin_attr->size);
> -}
> -
>  static int opal_add_one_export(struct kobject *parent, const char
> *export_name, struct device_node *np, const char *prop_name)
>  {
> @@ -826,7 +818,7 @@ static int opal_add_one_export(struct kobject
> *parent, const char *export_name, sysfs_bin_attr_init(attr);
>  	attr->attr.name = name;
>  	attr->attr.mode = 0400;
> -	attr->read = export_attr_read;
> +	attr->read = sysfs_bin_attr_simple_read;
>  	attr->private = __va(vals[0]);
>  	attr->size = vals[1];
>  
> diff --git a/drivers/acpi/bgrt.c b/drivers/acpi/bgrt.c
> index e4fb9e2..d1d9c92 100644
> --- a/drivers/acpi/bgrt.c
> +++ b/drivers/acpi/bgrt.c
> @@ -29,14 +29,7 @@
>  BGRT_SHOW(xoffset, image_offset_x);
>  BGRT_SHOW(yoffset, image_offset_y);
>  
> -static ssize_t image_read(struct file *file, struct kobject *kobj,
> -	       struct bin_attribute *attr, char *buf, loff_t off,
> size_t count) -{
> -	memcpy(buf, attr->private + off, count);
> -	return count;
> -}
> -
> -static BIN_ATTR_RO(image, 0);	/* size gets filled in later */
> +static BIN_ATTR_SIMPLE_RO(image);
>  
>  static struct attribute *bgrt_attributes[] = {
>  	&bgrt_attr_version.attr,
> diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
> index 015c95a..3d0f773 100644
> --- a/drivers/firmware/dmi_scan.c
> +++ b/drivers/firmware/dmi_scan.c
> @@ -746,16 +746,8 @@ static void __init dmi_scan_machine(void)
>  	pr_info("DMI not present or invalid.\n");
>  }
>  
> -static ssize_t raw_table_read(struct file *file, struct kobject
> *kobj,
> -			      struct bin_attribute *attr, char *buf,
> -			      loff_t pos, size_t count)
> -{
> -	memcpy(buf, attr->private + pos, count);
> -	return count;
> -}
> -
> -static BIN_ATTR(smbios_entry_point, S_IRUSR, raw_table_read, NULL,
> 0); -static BIN_ATTR(DMI, S_IRUSR, raw_table_read, NULL, 0);
> +static BIN_ATTR_SIMPLE_ADMIN_RO(smbios_entry_point);
> +static BIN_ATTR_SIMPLE_ADMIN_RO(DMI);
>  
>  static int __init dmi_init(void)
>  {
> diff --git a/drivers/firmware/efi/rci2-table.c
> b/drivers/firmware/efi/rci2-table.c index de1a9a1..4fd45d6 100644
> --- a/drivers/firmware/efi/rci2-table.c
> +++ b/drivers/firmware/efi/rci2-table.c
> @@ -40,15 +40,7 @@ struct rci2_table_global_hdr {
>  static u32 rci2_table_len;
>  unsigned long rci2_table_phys __ro_after_init =
> EFI_INVALID_TABLE_ADDR; 
> -static ssize_t raw_table_read(struct file *file, struct kobject
> *kobj,
> -			      struct bin_attribute *attr, char *buf,
> -			      loff_t pos, size_t count)
> -{
> -	memcpy(buf, attr->private + pos, count);
> -	return count;
> -}
> -
> -static BIN_ATTR(rci2, S_IRUSR, raw_table_read, NULL, 0);
> +static BIN_ATTR_SIMPLE_ADMIN_RO(rci2);
>  
>  static u16 checksum(void)
>  {
> diff --git a/drivers/gpu/drm/i915/gvt/firmware.c
> b/drivers/gpu/drm/i915/gvt/firmware.c index 4dd52ac..5e66a26 100644
> --- a/drivers/gpu/drm/i915/gvt/firmware.c
> +++ b/drivers/gpu/drm/i915/gvt/firmware.c
> @@ -50,21 +50,7 @@ struct gvt_firmware_header {
>  
>  #define dev_to_drm_minor(d) dev_get_drvdata((d))
>  
> -static ssize_t
> -gvt_firmware_read(struct file *filp, struct kobject *kobj,
> -	     struct bin_attribute *attr, char *buf,
> -	     loff_t offset, size_t count)
> -{
> -	memcpy(buf, attr->private + offset, count);
> -	return count;
> -}
> -
> -static struct bin_attribute firmware_attr = {
> -	.attr = {.name = "gvt_firmware", .mode = (S_IRUSR)},
> -	.read = gvt_firmware_read,
> -	.write = NULL,
> -	.mmap = NULL,
> -};
> +static BIN_ATTR_SIMPLE_ADMIN_RO(gvt_firmware);
>  
>  static int expose_firmware_sysfs(struct intel_gvt *gvt)
>  {
> @@ -107,10 +93,10 @@ static int expose_firmware_sysfs(struct
> intel_gvt *gvt) crc32_start = offsetof(struct gvt_firmware_header,
> version); h->crc32 = crc32_le(0, firmware + crc32_start, size -
> crc32_start); 
> -	firmware_attr.size = size;
> -	firmware_attr.private = firmware;
> +	bin_attr_gvt_firmware.size = size;
> +	bin_attr_gvt_firmware.private = firmware;
>  
> -	ret = device_create_bin_file(&pdev->dev, &firmware_attr);
> +	ret = device_create_bin_file(&pdev->dev,
> &bin_attr_gvt_firmware); if (ret) {
>  		vfree(firmware);
>  		return ret;
> @@ -122,8 +108,8 @@ static void clean_firmware_sysfs(struct intel_gvt
> *gvt) {
>  	struct pci_dev *pdev = to_pci_dev(gvt->gt->i915->drm.dev);
>  
> -	device_remove_bin_file(&pdev->dev, &firmware_attr);
> -	vfree(firmware_attr.private);
> +	device_remove_bin_file(&pdev->dev, &bin_attr_gvt_firmware);
> +	vfree(bin_attr_gvt_firmware.private);
>  }
>  
>  /**
> diff --git a/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
> b/drivers/thermal/intel/int340x_thermal/int3400_thermal.c index
> 427d370..6d4b51a 100644 ---
> a/drivers/thermal/intel/int340x_thermal/int3400_thermal.c +++
> b/drivers/thermal/intel/int340x_thermal/int3400_thermal.c @@ -73,14
> +73,7 @@ struct odvp_attr { struct device_attribute attr;
>  };
>  
> -static ssize_t data_vault_read(struct file *file, struct kobject
> *kobj,
> -	     struct bin_attribute *attr, char *buf, loff_t off,
> size_t count) -{
> -	memcpy(buf, attr->private + off, count);
> -	return count;
> -}
> -
> -static BIN_ATTR_RO(data_vault, 0);
> +static BIN_ATTR_SIMPLE_RO(data_vault);
>  
>  static struct bin_attribute *data_attributes[] = {
>  	&bin_attr_data_vault,
> diff --git a/init/initramfs.c b/init/initramfs.c
> index da79760..5193fae 100644
> --- a/init/initramfs.c
> +++ b/init/initramfs.c
> @@ -575,15 +575,7 @@ static int __init initramfs_async_setup(char
> *str) #include <linux/initrd.h>
>  #include <linux/kexec.h>
>  
> -static ssize_t raw_read(struct file *file, struct kobject *kobj,
> -			struct bin_attribute *attr, char *buf,
> -			loff_t pos, size_t count)
> -{
> -	memcpy(buf, attr->private + pos, count);
> -	return count;
> -}
> -
> -static BIN_ATTR(initrd, 0440, raw_read, NULL, 0);
> +static BIN_ATTR(initrd, 0440, sysfs_bin_attr_simple_read, NULL, 0);
>  
>  void __init reserve_initrd_mem(void)
>  {
> diff --git a/kernel/module/sysfs.c b/kernel/module/sysfs.c
> index d964167..26efe13 100644
> --- a/kernel/module/sysfs.c
> +++ b/kernel/module/sysfs.c
> @@ -146,17 +146,6 @@ struct module_notes_attrs {
>  	struct bin_attribute attrs[] __counted_by(notes);
>  };
>  
> -static ssize_t module_notes_read(struct file *filp, struct kobject
> *kobj,
> -				 struct bin_attribute *bin_attr,
> -				 char *buf, loff_t pos, size_t count)
> -{
> -	/*
> -	 * The caller checked the pos and count against our size.
> -	 */
> -	memcpy(buf, bin_attr->private + pos, count);
> -	return count;
> -}
> -
>  static void free_notes_attrs(struct module_notes_attrs *notes_attrs,
>  			     unsigned int i)
>  {
> @@ -205,7 +194,7 @@ static void add_notes_attrs(struct module *mod,
> const struct load_info *info) nattr->attr.mode = 0444;
>  			nattr->size = info->sechdrs[i].sh_size;
>  			nattr->private = (void
> *)info->sechdrs[i].sh_addr;
> -			nattr->read = module_notes_read;
> +			nattr->read = sysfs_bin_attr_simple_read;
>  			++nattr;
>  		}
>  		++loaded;

Re: [PATCH 2/2] treewide: Use sysfs_bin_attr_simple_read() helper

[Michael Ellerman]

Lukas Wunner <lukas@wunner.de> writes:
> Deduplicate ->read() callbacks of bin_attributes which are backed by a
> simple buffer in memory:
>
> Use the newly introduced sysfs_bin_attr_simple_read() helper instead,
> either by referencing it directly or by declaring such bin_attributes
> with BIN_ATTR_SIMPLE_RO() or BIN_ATTR_SIMPLE_ADMIN_RO().
>
> Aside from a reduction of LoC, this shaves off a few bytes from vmlinux
> (304 bytes on an x86_64 allyesconfig).
>
> No functional change intended.
>
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> ---
>  arch/powerpc/platforms/powernv/opal.c              | 10 +--------
>  drivers/acpi/bgrt.c                                |  9 +-------
>  drivers/firmware/dmi_scan.c                        | 12 ++--------
>  drivers/firmware/efi/rci2-table.c                  | 10 +--------
>  drivers/gpu/drm/i915/gvt/firmware.c                | 26 +++++-----------------
>  .../intel/int340x_thermal/int3400_thermal.c        |  9 +-------
>  init/initramfs.c                                   | 10 +--------
>  kernel/module/sysfs.c                              | 13 +----------
>  8 files changed, 14 insertions(+), 85 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
> index 45dd77e..5d0f35b 100644
> --- a/arch/powerpc/platforms/powernv/opal.c
> +++ b/arch/powerpc/platforms/powernv/opal.c
> @@ -792,14 +792,6 @@ static int __init opal_sysfs_init(void)
>  	return 0;
>  }
>  
> -static ssize_t export_attr_read(struct file *fp, struct kobject *kobj,
> -				struct bin_attribute *bin_attr, char *buf,
> -				loff_t off, size_t count)
> -{
> -	return memory_read_from_buffer(buf, count, &off, bin_attr->private,
> -				       bin_attr->size);
> -}
> -
>  static int opal_add_one_export(struct kobject *parent, const char *export_name,
>  			       struct device_node *np, const char *prop_name)
>  {
> @@ -826,7 +818,7 @@ static int opal_add_one_export(struct kobject *parent, const char *export_name,
>  	sysfs_bin_attr_init(attr);
>  	attr->attr.name = name;
>  	attr->attr.mode = 0400;
> -	attr->read = export_attr_read;
> +	attr->read = sysfs_bin_attr_simple_read;
>  	attr->private = __va(vals[0]);
>  	attr->size = vals[1];

I gave it a quick boot and checked I could still read the attributes,
everything seems fine.

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers

Re: [PATCH 0/2] Deduplicate bin_attribute simple read() callbacks

[Rafael J. Wysocki]

On Sat, Apr 6, 2024 at 3:52 PM Lukas Wunner <lukas@wunner.de> wrote:
>
> For my upcoming PCI device authentication v2 patches, I have the need
> to expose a simple buffer in virtual memory as a bin_attribute.
>
> It turns out we've duplicated the ->read() callback for such simple
> buffers a fair number of times across the tree.
>
> So instead of reinventing the wheel, I decided to introduce a common
> helper and eliminate all duplications I could find.
>
> I'm open to a bikeshedding discussion on the sysfs_bin_attr_simple_read()
> name. ;)
>
> Lukas Wunner (2):
>   sysfs: Add sysfs_bin_attr_simple_read() helper
>   treewide: Use sysfs_bin_attr_simple_read() helper
>
>  arch/powerpc/platforms/powernv/opal.c              | 10 +-------
>  drivers/acpi/bgrt.c                                |  9 +-------
>  drivers/firmware/dmi_scan.c                        | 12 ++--------
>  drivers/firmware/efi/rci2-table.c                  | 10 +-------
>  drivers/gpu/drm/i915/gvt/firmware.c                | 26 +++++----------------
>  .../intel/int340x_thermal/int3400_thermal.c        |  9 +-------
>  fs/sysfs/file.c                                    | 27 ++++++++++++++++++++++
>  include/linux/sysfs.h                              | 15 ++++++++++++
>  init/initramfs.c                                   | 10 +-------
>  kernel/module/sysfs.c                              | 13 +----------
>  10 files changed, 56 insertions(+), 85 deletions(-)
>
> --

For the series

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Re: [PATCH 1/2] sysfs: Add sysfs_bin_attr_simple_read() helper

[Greg Kroah-Hartman]

On Sat, Apr 06, 2024 at 03:52:01PM +0200, Lukas Wunner wrote:
> When drivers expose a bin_attribute in sysfs which is backed by a buffer
> in memory, a common pattern is to set the @private and @size members in
> struct bin_attribute to the buffer's location and size.
> 
> The ->read() callback then merely consists of a single memcpy() call.
> It's not even necessary to perform bounds checks as these are already
> handled by sysfs_kf_bin_read().
> 
> However each driver is so far providing its own ->read() implementation.
> The pattern is sufficiently frequent to merit a public helper, so add
> sysfs_bin_attr_simple_read() as well as BIN_ATTR_SIMPLE_RO() and
> BIN_ATTR_SIMPLE_ADMIN_RO() macros to ease declaration of such
> bin_attributes and reduce LoC and .text section size.
> 
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> ---
>  fs/sysfs/file.c       | 27 +++++++++++++++++++++++++++
>  include/linux/sysfs.h | 15 +++++++++++++++
>  2 files changed, 42 insertions(+)

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Re: [PATCH 0/2] Deduplicate bin_attribute simple read() callbacks

[Greg Kroah-Hartman]

On Sat, Apr 06, 2024 at 03:52:00PM +0200, Lukas Wunner wrote:
> For my upcoming PCI device authentication v2 patches, I have the need
> to expose a simple buffer in virtual memory as a bin_attribute.
> 
> It turns out we've duplicated the ->read() callback for such simple
> buffers a fair number of times across the tree.
> 
> So instead of reinventing the wheel, I decided to introduce a common
> helper and eliminate all duplications I could find.
> 
> I'm open to a bikeshedding discussion on the sysfs_bin_attr_simple_read()
> name. ;)

Seems like no one objects, should I just take this through my
driver-core tree for 6.10?

thanks,

greg k-h

Re: [PATCH 0/2] Deduplicate bin_attribute simple read() callbacks

[Lukas Wunner]

On Thu, Apr 11, 2024 at 03:07:46PM +0200, Greg Kroah-Hartman wrote:
> On Sat, Apr 06, 2024 at 03:52:00PM +0200, Lukas Wunner wrote:
> > For my upcoming PCI device authentication v2 patches, I have the need
> > to expose a simple buffer in virtual memory as a bin_attribute.
> > 
> > It turns out we've duplicated the ->read() callback for such simple
> > buffers a fair number of times across the tree.
> > 
> > So instead of reinventing the wheel, I decided to introduce a common
> > helper and eliminate all duplications I could find.
> > 
> > I'm open to a bikeshedding discussion on the sysfs_bin_attr_simple_read()
> > name. ;)
> 
> Seems like no one objects, should I just take this through my
> driver-core tree for 6.10?

That would be awesome, thank you!

Lukas