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The ath9k driver uses as maximum allowed txpower the constant MAX_RATE_POWER. It is used to set a maximum txpower limit for the PHY (which is combined txpower) and also the maximum txpower for per chain rates. Its value 63 is derived from the maximum number the registers can store for the per chain txpower. The max txpower a user can set because of this is 31 dBm (floor(63 / 2)). This also means that a device with multiple tx chains is even limited further: * 1 chain: 31 dBm per chain * 2 chains: 28 dBm per chain * 3 chains: 26 dBm per chain This combined txpower limit of 31 dBm becomes even more problematic when some extra antenna gain is set in the EEPROM. A high power device is then no longer able to reach its potential limits. Instead the code dealing with the combined txpower must use a higher limit than 63 and only the code dealing with the per chain txpower have to use the limit of 63. Since the antenna gain can be quite large and 8 bit variables are often used in ath9k for txpower, a large, divisible by two number like 254 is a good choice for this new limit. Signed-off-by: Sven Eckelmann <sven@narfation.org> Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Linux kernel
============
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