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net/wireless/chan.c: prohibited_flags wrongly set

DISCUSSION Arend van Spriel 3 participants 3 messages May 1, 2014 – May 2, 2014 1 message not in the archive

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Arend van Spriel

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#0 lore raw

Hi Johannes,

I was debugging issue with hostapd failing on setting channel when I came across this piece of code in chan.c:545:cfg80211_chandef_usable():

	if (width > 20)
		prohibited_flags |= IEEE80211_CHAN_NO_OFDM;

	/* 5 and 10 MHz are only defined for the OFDM PHY */
	if (width < 20)
		prohibited_flags |= IEEE80211_CHAN_NO_OFDM;

I suspect the first if statement to be wrong, but what should it be?

Regards,
Arend

#1 lore raw

2014-05-01 10:26 GMT+02:00 Arend van Spriel <[email protected]>:

Quoted 5 lines

Hi Johannes,

I was debugging issue with hostapd failing on setting channel when I came across this piece of code in chan.c:545:cfg80211_chandef_usable():

Quoted 9 lines
        if (width > 20)
                prohibited_flags |= IEEE80211_CHAN_NO_OFDM;

        /* 5 and 10 MHz are only defined for the OFDM PHY */
        if (width < 20)
                prohibited_flags |= IEEE80211_CHAN_NO_OFDM;

I suspect the first if statement to be wrong, but what should it be?

width > 20 - HT40, VHT80 ... - 80211n/80211ac using OFDM - so NO_OFDM
seems to be prohibited.

BR
Janusz

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#3 lore raw
Quoted 11 lines · Krishna Chaitanya
Quoted 8 lines · Arend van Spriel

Hi Johannes,

I was debugging issue with hostapd failing on setting channel when I came across this piece of code in chan.c:545:cfg80211_chandef_usable():

        if (width > 20)
                prohibited_flags |= IEEE80211_CHAN_NO_OFDM;
Quoted 7 lines
Quoted 5 lines
        /* 5 and 10 MHz are only defined for the OFDM PHY */
        if (width < 20)
                prohibited_flags |= IEEE80211_CHAN_NO_OFDM;

I suspect the first if statement to be wrong, but what should it be?

Looks ok to me. Basically it says that only 20MHz has a possibility of both OFDM and DSSS.

Adding the list.