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authorTian Tao <tiantao6@hisilicon.com>2021-08-06 23:02:47 +1200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-08-13 10:27:49 +0200
commit1fae562983ca5c7eb36d4974be5e235374661806 (patch)
tree4dbe10e1362c47548bc2c85a2e08f8a730dd94bb /include/linux/bitmap.h
parentbd935a7b21340e2e37f51a7f2d3188145e2fcf1f (diff)
cpumask: introduce cpumap_print_list/bitmask_to_buf to support large bitmask and list
The existing cpumap_print_to_pagebuf() is used by cpu topology and other drivers to export hexadecimal bitmask and decimal list to userspace by sysfs ABI. Right now, those drivers are using a normal attribute for this kind of ABIs. A normal attribute typically has show entry as below: static ssize_t example_dev_show(struct device *dev, struct device_attribute *attr, char *buf) { ... return cpumap_print_to_pagebuf(true, buf, &pmu_mmdc->cpu); } show entry of attribute has no offset and count parameters and this means the file is limited to one page only. cpumap_print_to_pagebuf() API works terribly well for this kind of normal attribute with buf parameter and without offset, count: static inline ssize_t cpumap_print_to_pagebuf(bool list, char *buf, const struct cpumask *mask) { return bitmap_print_to_pagebuf(list, buf, cpumask_bits(mask), nr_cpu_ids); } The problem is once we have many cpus, we have a chance to make bitmask or list more than one page. Especially for list, it could be as complex as 0,3,5,7,9,...... We have no simple way to know it exact size. It turns out bin_attribute is a way to break this limit. bin_attribute has show entry as below: static ssize_t example_bin_attribute_show(struct file *filp, struct kobject *kobj, struct bin_attribute *attr, char *buf, loff_t offset, size_t count) { ... } With the new offset and count parameters, this makes sysfs ABI be able to support file size more than one page. For example, offset could be >= 4096. This patch introduces cpumap_print_bitmask/list_to_buf() and their bitmap infrastructure bitmap_print_bitmask/list_to_buf() so that those drivers can move to bin_attribute to support large bitmask and list. At the same time, we have to pass those corresponding parameters such as offset, count from bin_attribute to this new API. Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Stefano Brivio <sbrivio@redhat.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: "Ma, Jianpeng" <jianpeng.ma@intel.com> Cc: Yury Norov <yury.norov@gmail.com> Cc: Valentin Schneider <valentin.schneider@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Signed-off-by: Tian Tao <tiantao6@hisilicon.com> Signed-off-by: Barry Song <song.bao.hua@hisilicon.com> Link: https://lore.kernel.org/r/20210806110251.560-2-song.bao.hua@hisilicon.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux/bitmap.h')
-rw-r--r--include/linux/bitmap.h6
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index a36cfcec4e77..37f36dad18bd 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -227,6 +227,12 @@ unsigned int bitmap_ord_to_pos(const unsigned long *bitmap, unsigned int ord, un
int bitmap_print_to_pagebuf(bool list, char *buf,
const unsigned long *maskp, int nmaskbits);
+extern int bitmap_print_bitmask_to_buf(char *buf, const unsigned long *maskp,
+ int nmaskbits, loff_t off, size_t count);
+
+extern int bitmap_print_list_to_buf(char *buf, const unsigned long *maskp,
+ int nmaskbits, loff_t off, size_t count);
+
#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
#define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))