Messages in this thread | | | From | Kyle Moffett <> | Subject | Re: Add a "enable" sysfs attribute to the pci devices to allow userspace (Xorg) to enable devices without doing foul direct access | Date | Sun, 7 May 2006 15:07:08 -0400 |
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On May 7, 2006, at 08:05:59, Krzysztof Halasa wrote: > Kyle Moffett <mrmacman_g4@mac.com> writes: >> Jon Smirl gave a great description of exactly how to write such a >> "driver". I seem to recall that we already have the ability to >> trigger manual PCI binding by bus:slot number; in combination with >> an appropriate "write EEPROM with firmware file" driver that has >> no default list of PCI devices; you could easily manually trigger >> a bind of the device. > > Writing EEPROM is not a problem and can be done safely from user > space (mmap /dev/mem).
This is *exactly* what we don't want to do! The whole point of this thread is to prevent the need to use /dev/mem and /dev/kmem for anything except debugging.
> Doing it in the kernel seems like an overkill, especially if you do > the operation once in few years it's much easier to just download a > (statically linked?) binary than messing with the kernel.
Ewww, I certainly wouldn't trust a binary statically-linked binary program that mmaps /dev/mem or /dev/kmem, and I certainly bet that 90% of the people on this list would feel likewise. We'd much prefer a program which does this:
#! /bin/sh cp firmware.bin /lib/firmware/some_firmware_file.bin echo -n eeprom_load_driver >/sys/device/$PCI_ID/bind echo -n 1 >/sys/device/$PCI_ID/unbind
Simple, obviously correct, and uses a nice reuseable driver too!
> It doesn't even interfere with the "main" driver and can be done > while the device is operating (given that previous EEPROM made > sense, otherwise the driver would not load).
No! That would be even worse! You're then having userspace poke at the driver while a kernel driver is loaded, which is *exactly* what X is getting into trouble for doing. If you want to add firmware update capability, add it to the preexisting primary driver.
>> In any case what you really need for all those cases is a >> simplistic stub driver that provides some sort of in-kernel mutual >> exclusion. > > Right. I.e., "enable" interface with, possibly, locking mechanism, > instead of some per-class "driver".
No, not an "enable" interface. In this case the kernel should do basically all of the poking at PCI resources for you. If you _really_ want to do that kind of update in userspace, write a stub driver which just enables the device on bind, disables it on unbind, and mmap and write to the sysfs "rom" file.
Cheers, Kyle Moffett
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