[PATCH iwinfo 2/4] iwinfo: nl80211: skip ftd and mtd lookups for usb devices

[Andre Heider]

Determine if parent device of the phy belongs to the "usb" subsystem
and skip those expensive lookups accordingly. Those don't even make any
sense for usb devices.

With a 5.15 kernel the mtd lookup even spams dmesg with:
"mtdblock: MTD device 'factory' is NAND, please consider using UBI block
devices instead."

Before:
sys     0m 3.56s$

After:
sys     0m 0.09s

Signed-off-by: Andre Heider <a.heider at gmail.com>
---
 iwinfo_nl80211.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/iwinfo_nl80211.c b/iwinfo_nl80211.c
index ba92530..fcc48dd 100644
--- a/iwinfo_nl80211.c
+++ b/iwinfo_nl80211.c
@@ -3455,7 +3455,8 @@ static int nl80211_hardware_id_from_fdt(struct iwinfo_hardware_id *id, const cha
 static int nl80211_get_hardware_id(const char *ifname, char *buf)
 {
 	struct iwinfo_hardware_id *id = (struct iwinfo_hardware_id *)buf;
-	char *phy, num[8], path[PATH_MAX];
+	char *phy, *p, num[8], link[PATH_MAX], path[PATH_MAX];
+	bool usb = false;
 	int i;
 
 	struct { const char *path; uint16_t *dest; } lookup[] = {
@@ -3470,6 +3471,16 @@ static int nl80211_get_hardware_id(const char *ifname, char *buf)
 	/* Try to determine the phy name from the given interface */
 	phy = nl80211_ifname2phy(ifname);
 
+	snprintf(path, sizeof(path), "/sys/class/%s/%s/device/subsystem",
+	         phy ? "ieee80211" : "net",
+	         phy ? phy : ifname);
+
+	if (realpath(path, link)) {
+		p = strrchr(link, '/');
+		if (p)
+			usb = strcmp(p + 1, "usb") == 0;
+	}
+
 	for (i = 0; i < ARRAY_SIZE(lookup); i++)
 	{
 		snprintf(path, sizeof(path), "/sys/class/%s/%s/device/%s",
@@ -3480,14 +3491,16 @@ static int nl80211_get_hardware_id(const char *ifname, char *buf)
 			*lookup[i].dest = strtoul(num, NULL, 16);
 	}
 
-	/* Failed to obtain hardware IDs, try FDT */
-	if (id->vendor_id == 0 || id->device_id == 0)
-		if (!nl80211_hardware_id_from_fdt(id, ifname))
-			return 0;
+	if (!usb) {
+		/* Failed to obtain hardware IDs, try FDT */
+		if (id->vendor_id == 0 || id->device_id == 0)
+			if (!nl80211_hardware_id_from_fdt(id, ifname))
+				return 0;
 
-	/* Failed to obtain hardware IDs, search board config */
-	if (id->vendor_id == 0 || id->device_id == 0)
-		return iwinfo_hardware_id_from_mtd(id);
+		/* Failed to obtain hardware IDs, search board config */
+		if (id->vendor_id == 0 || id->device_id == 0)
+			return iwinfo_hardware_id_from_mtd(id);
+	}
 
 	return 0;
 }
-- 
2.35.1