On 10/15/2014 06:32 AM, Octavian Purdila wrote:
On Wed, Oct 15, 2014 at 4:13 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
On 10/15/2014 04:49 AM, Octavian Purdila wrote:
On Tue, Oct 14, 2014 at 6:41 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
On Tue, Oct 14, 2014 at 05:48:14PM +0300, Octavian Purdila wrote:
This patch adds three new sysfs files: bus_frequency,
bus_min_frequency and bus_max_frequency which allows the user to view
or change the bus frequency on a per bus level.
<snip>
+
+static DEVICE_ATTR(bus_frequency, S_IRUGO, i2c_sysfs_freq_show,
+ i2c_sysfs_freq_store);
Consider using DEVICE_ATTR_RO here. Also, extra empty line.
Unfortunately that won't work because we must transform bus_frequency
to a RW entry (via is_visible) if the bus can change the frequency. We
Ah yes, you are right.
can't use DEVIE_ATTR_RW either, because transforming a RW entry to a
RO entry with is visible is not possible:
Why not ?
is_visible returns the desired mode. Just like you can return mode |
S_IWUSR,
you can return mode & ~S_IWUSR.
Am I missing something ?
Here is how sysfs uses is_visible:
static int create_files(struct kernfs_node *parent, struct kobject *kobj,
...
if (grp->is_visible) {
mode = grp->is_visible(kobj, *attr, i);
if (!mode)
continue;
}
error = sysfs_add_file_mode_ns(parent, *attr, false,
(*attr)->mode | mode,
NULL);
so basically is the mode set is the original mode from the attributed
"or-ed" with the mode return by is_visible.
Ah, you are right. That's a new one for me. Thanks, I didn't notice earlier.
Good to know ;-).
Guenter
--
To unsubscribe from this list: send the line "unsubscribe linux-api" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
