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SubjectRE: Patching ath9k/mac80211 to change MAC layer features
Date

Hi,

I would appreciate if anyone can help me with my previous query as soon as possible.
Thanks!
From: fredmm@hotmail.co.uk
To: linux-kernel@vger.kernel.org; linux-wireless@vger.kernel.org; ath9k-devel@venema.h4ckr.net; ath9k-devel@lists.ath9k
Subject: Patching ath9k/mac80211 to change MAC layer features
Date: Thu, 16 Jun 2011 21:39:09 +0100


Hello all,

I have a query regarding patching ath9k/mac80211 to change MAC layer features and I would be most grateful if someone can assist.

I need to patch ath9k so that I can be able to modify/fix the A-MPDU aggregation frame length and other parameters such that they can be configured at runtime via debugfs. I made a newbie attempt at trying to change the aggregate length (attached), but I am unsure of the correctness/efficiency  - when applied throughput varies with different frame lengths entered but I can't be sure if its actually changing the aggregation length (passes the framelen/aggr_limit). Hence I would be very grateful if someone can assist in the correct way of doing this (possibly directly via mac80211).

Also if the ampdu aggregate length is changed I believe the number/length of the subframes of the aggregate stays constant (at the default which is 32). I try to change this in my patch as well as the maximum software retries by just changing the default definition in ath9k.h, thus is there a (more) correct/better way of changing these. Finally, how can I patch the driver to be able to disable Block-Acks/aggregation via debugfs or otherwise.

I highly appreciate, help in any of the above, as well as other advice,
Many thanks
diff -Naur a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
--- a/drivers/net/wireless/ath/ath9k/ath9k.h 2011-05-27 20:04:49.000000000 +0100
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h 2011-06-02 19:59:28.043327000 +0100
@@ -137,7 +137,7 @@
#define ATH_AGGR_ENCRYPTDELIM 10
/* minimum h/w qdepth to be sustained to maximize aggregation */
#define ATH_AGGR_MIN_QDEPTH 2
-#define ATH_AMPDU_SUBFRAME_DEFAULT 32
+#define ATH_AMPDU_SUBFRAME_DEFAULT sc->debug.subframe_size

#define IEEE80211_SEQ_SEQ_SHIFT 4
#define IEEE80211_SEQ_MAX 4096
@@ -537,7 +537,7 @@
#define DEFAULT_CACHELINE 32
#define ATH_REGCLASSIDS_MAX 10
#define ATH_CABQ_READY_TIME 80 /* % of beacon interval */
-#define ATH_MAX_SW_RETRIES 10
+#define ATH_MAX_SW_RETRIES sc->debug.retry_limit
#define ATH_CHAN_MAX 255

#define ATH_TXPOWER_MAX 100 /* .5 dBm units */
diff -Naur a/drivers/net/wireless/ath/ath9k/debug.c b/drivers/net/wireless/ath/ath9k/debug.c
--- a/drivers/net/wireless/ath/ath9k/debug.c 2011-05-27 20:04:49.000000000 +0100
+++ b/drivers/net/wireless/ath/ath9k/debug.c 2011-06-02 19:54:09.260320000 +0100
@@ -1045,6 +1048,162 @@
.llseek = default_llseek,
};

+static ssize_t read_file_ampdu_len(struct file *file, char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct ath_softc *sc = file->private_data;
+ char buf[32];
+ unsigned int len;
+
+ len = sprintf(buf, "%u\n", sc->debug.ampdu_len);
+ return simple_read_from_buffer(user_buf, count, ppos, buf, len);
+}
+
+static ssize_t write_file_ampdu_len(struct file *file, const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct ath_softc *sc = file->private_data;
+ unsigned long ampdu_len;
+ char buf[32];
+ ssize_t len;
+
+ len = min(count, sizeof(buf) - 1);
+ if (copy_from_user(buf, user_buf, len))
+ return -EFAULT;
+
+ buf[len] = '\0';
+ if (strict_strtoul(buf, 0, &ampdu_len))
+ return -EINVAL;
+
+ sc->debug.ampdu_len = ampdu_len;
+ return count;
+}
+
+static const struct file_operations fops_ampdu_len = {
+ .read = read_file_ampdu_len,
+ .write = write_file_ampdu_len,
+ .open = ath9k_debugfs_open,
+ .owner = THIS_MODULE,
+ .llseek = default_llseek,
+};
+
+static ssize_t read_file_retry_limit(struct file *file, char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct ath_softc *sc = file->private_data;
+ char buf[16];
+ unsigned int len;
+
+ len = sprintf(buf, "%u\n", sc->debug.retry_limit);
+ return simple_read_from_buffer(user_buf, count, ppos, buf, len);
+}
+
+static ssize_t write_file_retry_limit(struct file *file, const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct ath_softc *sc = file->private_data;
+ unsigned long retry_limit;
+ char buf[16];
+ ssize_t len;
+
+ len = min(count, sizeof(buf) - 1);
+ if (copy_from_user(buf, user_buf, len))
+ return -EFAULT;
+
+ buf[len] = '\0';
+ if (strict_strtoul(buf, 0, &retry_limit))
+ return -EINVAL;
+
+ sc->debug.retry_limit = retry_limit;
+ return count;
+}
+
+static const struct file_operations fops_retry_limit = {
+ .read = read_file_retry_limit,
+ .write = write_file_retry_limit,
+ .open = ath9k_debugfs_open,
+ .owner = THIS_MODULE,
+ .llseek = default_llseek,
+};
+
+static ssize_t read_file_subframe_size(struct file *file, char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct ath_softc *sc = file->private_data;
+ char buf[16];
+ unsigned int len;
+
+ len = sprintf(buf, "%u\n", sc->debug.subframe_size);
+ return simple_read_from_buffer(user_buf, count, ppos, buf, len);
+}
+
+static ssize_t write_file_subframe_size(struct file *file, const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct ath_softc *sc = file->private_data;
+ unsigned long subframe_size;
+ char buf[16];
+ ssize_t len;
+
+ len = min(count, sizeof(buf) - 1);
+ if (copy_from_user(buf, user_buf, len))
+ return -EFAULT;
+
+ buf[len] = '\0';
+ if (strict_strtoul(buf, 0, &subframe_size))
+ return -EINVAL;
+
+ sc->debug.subframe_size = subframe_size;
+ return count;
+}
+
+static const struct file_operations fops_subframe_size = {
+ .read = read_file_subframe_size,
+ .write = write_file_subframe_size,
+ .open = ath9k_debugfs_open,
+ .owner = THIS_MODULE,
+ .llseek = default_llseek,
+};
+
+static ssize_t read_file_auto_ampdu(struct file *file, char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct ath_softc *sc = file->private_data;
+ char buf[8];
+ unsigned int len;
+
+ len = sprintf(buf, "%u\n", sc->debug.auto_ampdu);
+ return simple_read_from_buffer(user_buf, count, ppos, buf, len);
+}
+
+static ssize_t write_file_auto_ampdu(struct file *file, const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct ath_softc *sc = file->private_data;
+ unsigned long auto_ampdu;
+ char buf[8];
+ ssize_t len;
+
+ len = min(count, sizeof(buf) - 1);
+ if (copy_from_user(buf, user_buf, len))
+ return -EFAULT;
+
+ buf[len] = '\0';
+ if (strict_strtoul(buf, 0, &auto_ampdu))
+ return -EINVAL;
+
+ sc->debug.auto_ampdu = auto_ampdu;
+ return count;
+}
+
+static const struct file_operations fops_auto_ampdu = {
+ .read = read_file_auto_ampdu,
+ .write = write_file_auto_ampdu,
+ .open = ath9k_debugfs_open,
+ .owner = THIS_MODULE,
+ .llseek = default_llseek,
+};
+
static ssize_t read_file_regval(struct file *file, char __user *user_buf,
size_t count, loff_t *ppos)
{
@@ -1162,6 +1407,15 @@
sc->debug.debugfs_phy, sc, &fops_tx_chainmask);
debugfs_create_file("regidx", S_IRUSR | S_IWUSR, sc->debug.debugfs_phy,
sc, &fops_regidx);
+
+ debugfs_create_file("ampdu_len", S_IRUSR | S_IWUSR, sc->debug.debugfs_phy,
+ sc, &fops_ampdu_len);
+ debugfs_create_file("retry_limit", S_IRUSR | S_IWUSR, sc->debug.debugfs_phy,
+ sc, &fops_retry_limit);
+ debugfs_create_file("subframe_size", S_IRUSR | S_IWUSR, sc->debug.debugfs_phy,
+ sc, &fops_subframe_size);
+ debugfs_create_file("auto_ampdu[0:OFF,1:ON]", S_IRUSR | S_IWUSR, sc->debug.debugfs_phy,
+ sc, &fops_auto_ampdu);
debugfs_create_file("regval", S_IRUSR | S_IWUSR, sc->debug.debugfs_phy,
sc, &fops_regval);
debugfs_create_bool("ignore_extcca", S_IRUSR | S_IWUSR,
@@ -1177,5 +1302,8 @@
sc->debug.debugfs_phy, &sc->sc_ah->gpio_val);

sc->debug.regidx = 0;
+ sc->debug.auto_ampdu = 1;
+ sc->debug.ampdu_len = ATH_AMPDU_LIMIT_MAX;
+ sc->debug.retry_limit = 10;
return 0;
}
diff -Naur a/drivers/net/wireless/ath/ath9k/debug.h b/drivers/net/wireless/ath/ath9k/debug.h
--- a/drivers/net/wireless/ath/ath9k/debug.h 2011-05-27 20:04:49.000000000 +0100
+++ b/drivers/net/wireless/ath/ath9k/debug.h 2011-06-02 19:55:33.332337000 +0100
@@ -179,6 +180,10 @@
struct ath9k_debug {
struct dentry *debugfs_phy;
u32 regidx;
+ u32 ampdu_len;
+ u16 retry_limit;
+ u16 subframe_size;
+ u8 auto_ampdu;
struct ath_stats stats;
};

diff -Naur a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
--- a/drivers/net/wireless/ath/ath9k/xmit.c 2011-05-27 20:04:49.000000000 +0100
+++ b/drivers/net/wireless/ath/ath9k/xmit.c 2011-06-02 19:58:19.647347000 +0100
@@ -616,8 +616,12 @@
if (rates[i].flags & IEEE80211_TX_RC_SHORT_GI)
modeidx++;

- frmlen = ath_max_4ms_framelen[modeidx][rates[i].idx];
- max_4ms_framelen = min(max_4ms_framelen, frmlen);
+ frmlen = ath_max_4ms_framelen[modeidx][rates[i].idx];
+
+ if (sc->debug.auto_ampdu==1)
+ max_4ms_framelen = min(max_4ms_framelen, frmlen);
+ else
+ max_4ms_framelen = sc->debug.ampdu_len;
}
}

@@ -641,7 +645,7 @@
* The IE, however can hold up to 65536, which shows up here
* as zero. Ignore 65536 since we are constrained by hw.
*/
- if (tid->an->maxampdu)
+ if (sc->debug.auto_ampdu==1 && tid->an->maxampdu)
aggr_limit = min(aggr_limit, tid->an->maxampdu);

return aggr_limit;
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