4 ms·

Wifi is even worse than i.e. the bug in the article because often it's some registers that are off or some firmware bug or even chip bug - so you are basically

by nisa 6y ago

Wifi is even worse than i.e. the bug in the article because often it's some registers that are off or some firmware bug or even chip bug - so you are basically helpless without intimate knowledge about the chip in question (only with NDA if at all). Much respect to anyone hacking on wifi (or anything else) in the kernel!

sigjuice 6y ago
"Firmware" in a lot of cases is a full-blown proprietary black box operating system of its own.
cjbprime 6y ago
And if you're lucky, then the wifi chip will helpfully corrupt your RAM with its terrible DMA mismanagement in a way that allows you to notice that the memory you were expecting to contain your own values instead contains the ESSID of the hospital across the road from you: https://mjg59.dreamwidth.org/11235.html https://mjg59.dreamwidth.org/11235.html
joecool1029 6y ago
I remember back in 2005 or so Intel was dicking around with ipw3945 shipping a userspace regulatory blob. Linux kernel devs didn't like this, I guess wouldn't merge the driver. Intel rewrote the driver into iwlwifi (iwl3945) which just loaded a microcode out of the firmware directory. However, the NDA compartmentalization issue would cause bugs. For instance, I guess the wifi microcode devs implemented hardware queuing but the intel kernel driver devs at the time didn't know this, so the driver devs just wrote their own queues in software and the users dealt with weird errors for some time because they literally couldn't ask the division that wrote the microcode how the hell it worked. I'm amazed anything with wifi works. For a time around then I just threw up my hands and used OpenBSD's reverse-engineered driver because it was more reliable and simple to understand.
non-entity 6y ago
I once tried to chase a bug in a wifi driver on NetBSD and soon gave up as I was just completely lost. I also remember buying a book on driver development, hoping there would be some decent info on the 802.11 stack and was mildy amused to find a breif mention at the end of a chapter describing ethernet internet saying "sorry wifi is too complicated to cover". Since that and about half a dozen other wifi kernel issues? I've been kinda fascinated by wifi and wifi stacks in the kerbel, but it appears to be some black magic power not available to the masses

by nisa 6y ago

sigjuice 6y ago

"Firmware" in a lot of cases is a full-blown proprietary black box operating system of its own.

cjbprime 6y ago

And if you're lucky, then the wifi chip will helpfully corrupt your RAM with its terrible DMA mismanagement in a way that allows you to notice that the memory you were expecting to contain your own values instead contains the ESSID of the hospital across the road from you: https://mjg59.dreamwidth.org/11235.html https://mjg59.dreamwidth.org/11235.html

joecool1029 6y ago

I remember back in 2005 or so Intel was dicking around with ipw3945 shipping a userspace regulatory blob. Linux kernel devs didn't like this, I guess wouldn't merge the driver. Intel rewrote the driver into iwlwifi (iwl3945) which just loaded a microcode out of the firmware directory. However, the NDA compartmentalization issue would cause bugs. For instance, I guess the wifi microcode devs implemented hardware queuing but the intel kernel driver devs at the time didn't know this, so the driver devs just wrote their own queues in software and the users dealt with weird errors for some time because they literally couldn't ask the division that wrote the microcode how the hell it worked. I'm amazed anything with wifi works. For a time around then I just threw up my hands and used OpenBSD's reverse-engineered driver because it was more reliable and simple to understand.

non-entity 6y ago

I once tried to chase a bug in a wifi driver on NetBSD and soon gave up as I was just completely lost. I also remember buying a book on driver development, hoping there would be some decent info on the 802.11 stack and was mildy amused to find a breif mention at the end of a chapter describing ethernet internet saying "sorry wifi is too complicated to cover". Since that and about half a dozen other wifi kernel issues? I've been kinda fascinated by wifi and wifi stacks in the kerbel, but it appears to be some black magic power not available to the masses