diff options
Diffstat (limited to 'drivers/fsi')
| -rw-r--r-- | drivers/fsi/fsi-core.c | 31 |
1 files changed, 27 insertions, 4 deletions
diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c index c773c65a5058..e02ebcb0c9e6 100644 --- a/drivers/fsi/fsi-core.c +++ b/drivers/fsi/fsi-core.c @@ -544,6 +544,31 @@ static int fsi_slave_scan(struct fsi_slave *slave) return 0; } +static unsigned long aligned_access_size(size_t offset, size_t count) +{ + unsigned long offset_unit, count_unit; + + /* Criteria: + * + * 1. Access size must be less than or equal to the maximum access + * width or the highest power-of-two factor of offset + * 2. Access size must be less than or equal to the amount specified by + * count + * + * The access width is optimal if we can calculate 1 to be strictly + * equal while still satisfying 2. + */ + + /* Find 1 by the bottom bit of offset (with a 4 byte access cap) */ + offset_unit = BIT(__builtin_ctzl(offset | 4)); + + /* Find 2 by the top bit of count */ + count_unit = BIT(8 * sizeof(unsigned long) - 1 - __builtin_clzl(count)); + + /* Constrain the maximum access width to the minimum of both criteria */ + return BIT(__builtin_ctzl(offset_unit | count_unit)); +} + static ssize_t fsi_slave_sysfs_raw_read(struct file *file, struct kobject *kobj, struct bin_attribute *attr, char *buf, loff_t off, size_t count) @@ -559,8 +584,7 @@ static ssize_t fsi_slave_sysfs_raw_read(struct file *file, return -EINVAL; for (total_len = 0; total_len < count; total_len += read_len) { - read_len = min_t(size_t, count, 4); - read_len -= off & 0x3; + read_len = aligned_access_size(off, count - total_len); rc = fsi_slave_read(slave, off, buf + total_len, read_len); if (rc) @@ -587,8 +611,7 @@ static ssize_t fsi_slave_sysfs_raw_write(struct file *file, return -EINVAL; for (total_len = 0; total_len < count; total_len += write_len) { - write_len = min_t(size_t, count, 4); - write_len -= off & 0x3; + write_len = aligned_access_size(off, count - total_len); rc = fsi_slave_write(slave, off, buf + total_len, write_len); if (rc) |