Ping-Ke Shih <pkshih@xxxxxxxxxxx> writes: > On Tue, 2024-07-16 at 01:19 +0000, Ping-Ke Shih wrote: > >> On Mon, 2024-07-15 at 14:26 +0300, Bitterblue Smith wrote: >> > On 15/07/2024 14:05, Bitterblue Smith wrote: >> > > Hi, >> > > >> > > To reproduce the problem, you need a computer with two wifi >> > > devices supported by rtw88. It's especially easy to notice >> > > the problem if one of the devices is USB and the other is PCI, >> > > because the PCI device will have various values in the >> > > registers 0x300..0x3ff, but the USB device will have all >> > > 0xeaeaeaea there. >> > > >> > > 1. Let's assume the driver for the PCI device is already loaded. >> > > I have RTL8822CE. >> > > >> > > 2. Mount debugfs: >> > > >> > > # mount -t debugfs none /sys/kernel/debug >> > > >> > > 3. Check page 0x300: >> > > >> > > # cat /sys/kernel/debug/ieee80211/phy0/rtw88/mac_3 >> > > 00000300 f7138000 33330000 ffffb000 00000000 >> > > ..... >> > > >> > > 4. Plug the USB device. I used RTL8811CU. >> > > >> > > 5. Check page 0x300 again: >> > > >> > > # cat /sys/kernel/debug/ieee80211/phy0/rtw88/mac_3 >> > > 00000300 eaeaeaea eaeaeaea eaeaeaea eaeaeaea >> > > ..... >> > > >> > > 6. Bonus: unload rtw88_8821cu and check page 0x300 again to get >> > > a null pointer dereference: >> > > >> > > # rmmod rtw88_8821cu >> > > # cat /sys/kernel/debug/ieee80211/phy0/rtw88/mac_3 >> > >> > I forgot to say: my kernel is 6.9.8-arch1-1 from Arch Linux. >> > The problem also happens with kernel 6.9.8 plus rtw88 from >> > rtw-next. >> >> This limitation is existing since initial driver. >> >> To read a range of large registers area, for example, we need to >> a range via write operation and store as a private data, and >> then use read operation with private data to read registers. >> >> The limitation is because the private data is static variable. >> A possible solution is to duplicate static variable into rtwdev. >> Not sure if it is worth to adjust codes for debug purpose only. >> >> Another easier solution is to avoid creating debugfs for second >> adapter. How do you think? >> > > Think a little bit further. I will try to duplicate static variables > to support multiple adapters. BTW in drivers all static variables need to be const just because of issues like this. Static non-const variables are a big no. -- https://patchwork.kernel.org/project/linux-wireless/list/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
