ath5k: reduce exported channel list

Claiming every available 5 ghz channel has a couple of negative
side-effects: scanning takes a long time, and the channel list
overflows the available buffer space for netlink commands,
resulting in:

    $ iw phy phy0 info
    command failed: No buffer space available (-105)

This patch adds a modparam so people who want to see all the channels
can do so by passing all_channels=1.  By default users will see a
smaller list of channels.  This also halves scan time, from 10 seconds
down to less than 5 when using world regulatory.

Changes-licensed-under: 3-Clause-BSD

Signed-off-by: Bob Copeland <me@bobcopeland.com>
Reported-by: Simon Farnsworth <simon@farnz.org.uk>
Tested-By: Simon Farnsworth <simon@farnz.org.uk>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/drivers/net/wireless/ath5k/base.c b/drivers/net/wireless/ath5k/base.c
index a08bc8a4fb69..d8c60c53d953 100644
--- a/drivers/net/wireless/ath5k/base.c
+++ b/drivers/net/wireless/ath5k/base.c
@@ -64,6 +64,10 @@ static int modparam_nohwcrypt;
 module_param_named(nohwcrypt, modparam_nohwcrypt, int, 0444);
 MODULE_PARM_DESC(nohwcrypt, "Disable hardware encryption.");
 
+static int modparam_all_channels;
+module_param_named(all_channels, modparam_all_channels, int, 0444);
+MODULE_PARM_DESC(all_channels, "Expose all channels the device can use.");
+
 
 /******************\
 * Internal defines *
@@ -862,6 +866,20 @@ ath5k_ieee2mhz(short chan)
                 return 2212 + chan * 20;
 }
 
+/*
+ * Returns true for the channel numbers used without all_channels modparam.
+ */
+static bool ath5k_is_standard_channel(short chan)
+{
+        return ((chan <= 14) ||
+                /* UNII 1,2 */
+                ((chan & 3) == 0 && chan >= 36 && chan <= 64) ||
+                /* midband */
+                ((chan & 3) == 0 && chan >= 100 && chan <= 140) ||
+                /* UNII-3 */
+                ((chan & 3) == 1 && chan >= 149 && chan <= 165));
+}
+
 static unsigned int
 ath5k_copy_channels(struct ath5k_hw *ah,
                 struct ieee80211_channel *channels,
@@ -899,6 +917,9 @@ ath5k_copy_channels(struct ath5k_hw *ah,
                 if (!ath5k_channel_ok(ah, freq, chfreq))
                         continue;
 
+                if (!modparam_all_channels && !ath5k_is_standard_channel(ch))
+                        continue;
+
                 /* Write channel info and increment counter */
                 channels[count].center_freq = freq;
                 channels[count].band = (chfreq == CHANNEL_2GHZ) ?