diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/bitmap.c | 33 |
1 files changed, 20 insertions, 13 deletions
diff --git a/lib/bitmap.c b/lib/bitmap.c index 0d5c2ece0bcb..8ebe508580ea 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -527,33 +527,39 @@ static int bitmap_print_to_buf(bool list, char *buf, const unsigned long *maskp, * cpumap_print_to_pagebuf() or directly by drivers to export hexadecimal * bitmask and decimal list to userspace by sysfs ABI. * Drivers might be using a normal attribute for this kind of ABIs. A - * normal attribute typically has show entry as below: - * static ssize_t example_attribute_show(struct device *dev, + * normal attribute typically has show entry as below:: + * + * static ssize_t example_attribute_show(struct device *dev, * struct device_attribute *attr, char *buf) - * { + * { * ... * return bitmap_print_to_pagebuf(true, buf, &mask, nr_trig_max); - * } + * } + * * show entry of attribute has no offset and count parameters and this * means the file is limited to one page only. * bitmap_print_to_pagebuf() API works terribly well for this kind of - * normal attribute with buf parameter and without offset, count: - * bitmap_print_to_pagebuf(bool list, char *buf, const unsigned long *maskp, + * normal attribute with buf parameter and without offset, count:: + * + * bitmap_print_to_pagebuf(bool list, char *buf, const unsigned long *maskp, * int nmaskbits) - * { - * } + * { + * } + * * The problem is once we have a large bitmap, we have a chance to get a * 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, + * 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. @@ -577,6 +583,7 @@ static int bitmap_print_to_buf(bool list, char *buf, const unsigned long *maskp, * This function is not a replacement for sprintf() or bitmap_print_to_pagebuf(). * It is intended to workaround sysfs limitations discussed above and should be * used carefully in general case for the following reasons: + * * - Time complexity is O(nbits^2/count), comparing to O(nbits) for snprintf(). * - Memory complexity is O(nbits), comparing to O(1) for snprintf(). * - @off and @count are NOT offset and number of bits to print. |