On 2020-11-06 18:25, Johannes Berg wrote:
Hi,
Looks pretty good. Some comments, mostly nits, below.
Thank you for the comments, Johannes.
I don't understand below well, please help explain:
And even if we do need the index, then perhaps we should use the
(otherwise anyway ignored) nla_type() of the container, instead of an
explicit inner attribute?
+/**
+ * nl80211_sar_attrs - Attributes for SAR spec
missing enum
sure
+ *
+ * @NL80211_SAR_ATTR_TYPE: the SAR type and it's defined in
%nl80211_sar_type.
better use &enum nl80211_sar_type for a link in docs
+ *
+ * @NL80211_SAR_ATTR_SPECS: Nested array of SAR power
+ * limit specifications. Each specification contains a set
+ * of %nl80211_sar_specs_attrs.
+ *
+ * For SET operation, it contains array of
NL80211_SAR_ATTR_SPECS_POWER
some odd indent?
Usually we just use a single tab.
sure
+/**
+ * nl80211_sar_specs_attrs - Attributes for SAR power limit specs
again, enum missing
+ *
+ * @NL80211_SAR_ATTR_SPECS_POWER: Required (u32)value to specify the
actual
+ * power limit value in units of 0.25 dBm if type is
+ * NL80211_SAR_TYPE_POWER. (i.e., a value of 44 represents 11 dBm).
+ * 0 means userspace doesn't have SAR limitation on this associated
range.
+ *
+ * @NL80211_SAR_ATTR_SPECS_RANGE_INDEX: Required (u32) value to
specify the
+ * index of exported freq range table and the associated power
limitation
+ * is applied to this range.
+ *
+ * Userspace isn't required to set all the ranges advertised by WLAN
driver,
+ * and userspace can skip some certain ranges. These skipped ranges
don't
+ * have SAR limitations, and these are same as setting the
+ * %NL80211_SAR_ATTR_SPECS_POWER to 0. But it's required to set at
least one range,
+ * no matter the power limiation is 0 or not.
(typo - limitation)
Should "0" really be the magic value? Theoretically, 0 and even
negative
values are valid. Perhaps we should just use something big (0xffffffff)
to indicate no limit, or just not have such a "no limitation" value
because userspace can always set it to something very big that means no
practical limitation anyway?
OK actually you have a U8 now so the high limit is 63.75dBm, but
there's
not really a good reason for that, since U32 takes the same space in
netlink anyway.
Looks 0 and negative value are not practical as it means <= 1mw,
but I can use S32 instead.
Not sure if a magic value is needed? If it's needed, then perhaps
0x7fffffff
is good for it?
And wait, I thought we agreed to remove the index? Now I'm confused.
Using index in SET operation doesn't add burden to userspace and kernel,
but it provides some flexibility so userspace can skip some certain
ranges.
And even if we do need the index, then perhaps we should use the
(otherwise anyway ignored) nla_type() of the container, instead of an
explicit inner attribute?
I don't understand what means here. Use nla_type for what?
+ *
+ * Every SET operation overwrites previous SET operation.
+ *
+ * @NL80211_SAR_ATTR_SPECS_START_FREQ: Required (u32) value to
specify the start
+ * frequency of this range edge when registering SAR capability to
wiphy. It's
+ * not a channel center frequency. The unit is KHz.
"kHz" not "KHz", in a few places other than this too
+static int
+nl80211_put_sar_specs(struct cfg80211_registered_device *rdev,
+ struct sk_buff *msg)
+{
+ struct nlattr *sar_capa, *specs, *sub_freq_range;
+ u8 num_freq_ranges;
extra space?
+ for (i = 0; i < num_freq_ranges; i++) {
+ sub_freq_range = nla_nest_start(msg, i + 1);
+
+ nla_put_u32(msg, NL80211_SAR_ATTR_SPECS_START_FREQ,
+ rdev->wiphy.sar_capa->freq_ranges[i].start_freq);
+
+ nla_put_u32(msg, NL80211_SAR_ATTR_SPECS_END_FREQ,
+ rdev->wiphy.sar_capa->freq_ranges[i].end_freq);
Need to check the return values of these three calls.
sure
And an aside, unrelated to this particular code: Should we do some kind
of validation that the ranges reported actually overlap all supported
channels (taking 20 MHz bandwidth into account)?
+ nla_parse_nested(tb, NL80211_SAR_ATTR_MAX,
info->attrs[NL80211_ATTR_SAR_SPEC],
+ sar_policy, info->extack);
If you're not checking the return value then no point in passing a
policy or extack :-)
And yes, it's already validated, so you don't have to do it again.
Yes, will use NULL instead of info->extack
+ sar_spec->type = type;
+ specs = 0;
+ nla_for_each_nested(spec_list, tb[NL80211_SAR_ATTR_SPECS], rem) {
+ if (nla_parse(spec,
+ NL80211_SAR_ATTR_SPECS_MAX,
+ nla_data(spec_list),
+ nla_len(spec_list),
+ sar_specs_policy,
+ NULL)) {
Similar here, don't really need to validate it since it's done by the
policy.
sure
+ err = -EINVAL;
+ goto error;
+ }
+
+ /* for power type, power value and index must be presented */
+ if ((!spec[NL80211_SAR_ATTR_SPECS_POWER] ||
+ !spec[NL80211_SAR_ATTR_SPECS_RANGE_INDEX]) &&
+ type == NL80211_SAR_TYPE_POWER) {
maybe "switch (type) {...}" or something and return -EINVAL also if
it's
a type not supported in the code yet, i.e. default case?
Otherwise we might add a type, and forget this pretty easily.
Good suggestion, will change to switch case.
+ err = -EINVAL;
+ goto error;
+ }
+
+ power = nla_get_u8(spec[NL80211_SAR_ATTR_SPECS_POWER]);
+ sar_spec->sub_specs[specs].power = power;
and that probably should then be in a sub function or something also
inside the particular type.
or maybe just all in a separate function? dunno. not really
_necessary_,
but the lines are getting kinda long already, and one more indentation
level with the switch won't help ...
I'll move this to a separate function.
johannes
