疑问？？？？

root@hbg:/# iw phy phy0 info
Wiphy phy0
        max # scan SSIDs: 4
        max scan IEs length: 2257 bytes
        Retry short limit: 7
        Retry long limit: 4
        Coverage class: 5 (up to 2250m)     // 这个是用来干嘛的，等级是如何划分的？
        Device supports AP-side u-APSD.
        Device supports T-DLS.
        Available Antennas: TX 0x3 RX 0x3
        Configured Antennas: TX 0x1 RX 0x1
        Supported interface modes:
                 * IBSS
                 * managed
                 * AP
                 * AP/VLAN
                 * WDS
                 * monitor
                 * mesh point
                 * P2P-client
                 * P2P-GO
        Band 1:
                Capabilities: 0x11ef
                        RX LDPC
                        HT20/HT40
                        SM Power Save disabled
                        RX HT20 SGI
                        RX HT40 SGI
                        TX STBC
                        RX STBC 1-stream
                        Max AMSDU length: 3839 bytes
                        DSSS/CCK HT40
                Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
                Minimum RX AMPDU time spacing: 8 usec (0x06)
                HT TX/RX MCS rate indexes supported: 0-7
                Frequencies:
                        * 2412 MHz [1] (19.0 dBm)
                        * 2417 MHz [2] (19.0 dBm)
                        * 2422 MHz [3] (19.0 dBm)
                        * 2427 MHz [4] (19.0 dBm)
                        * 2432 MHz [5] (19.0 dBm)
                        * 2437 MHz [6] (19.0 dBm)
                        * 2442 MHz [7] (19.0 dBm)
                        * 2447 MHz [8] (19.0 dBm)
                        * 2452 MHz [9] (19.0 dBm)
                        * 2457 MHz [10] (19.0 dBm)
                        * 2462 MHz [11] (19.0 dBm)
                        * 2467 MHz [12] (disabled)
                        * 2472 MHz [13] (disabled)
                        * 2484 MHz [14] (disabled)
        valid interface combinations:
                 * #{ managed } <= 2048, #{ AP, mesh point } <= 8, #{ P2P-client, P2P-GO } <= 1, #{ IBSS } <= 1,
                   total <= 2048, #channels <= 1, STA/AP BI must match
                 * #{ WDS } <= 2048,
                   total <= 2048, #channels <= 1, STA/AP BI must match
                 * #{ IBSS, AP, mesh point } <= 1,
                   total <= 1, #channels <= 1, STA/AP BI must match, radar detect widths: { 20 MHz (no HT), 20 MHz, 40 MHz }

        HT Capability overrides:
                 * MCS: ff ff ff ff ff ff ff ff ff ff
                 * maximum A-MSDU length
                 * supported channel width
                 * short GI for 40 MHz
                 * max A-MPDU length exponent
                 * min MPDU start spacing
root@hbg:/#