Messages in this thread | | | Subject | Re: [RFC] Pushing device/driver binding decisions to userspace | From | Ben Collins <> | Date | Sun, 12 Nov 2006 23:10:45 -0800 |
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On Sun, 2006-11-12 at 22:45 -0800, Nicholas Miell wrote: > On Sun, 2006-11-12 at 21:22 -0800, Ben Collins wrote: > > On Sun, 2006-11-12 at 17:47 -0800, Nicholas Miell wrote: > > > On Sun, 2006-11-12 at 17:24 -0800, Ben Collins wrote: > > > > On Sun, 2006-11-12 at 16:49 -0800, Nicholas Miell wrote: > > > > > On Sun, 2006-11-12 at 15:39 -0800, Ben Collins wrote: > > > > > > > > > > What's wrong with making udev or whatever unbind driver A and then bind > > > > > driver B if the driver bound by the kernel ends up being the wrong > > > > > choice? (Besides the inelegance of the kernel choosing one and then > > > > > userspace immediately choosing the other, of course.) > > > > > > > > > > I'd argue that having multiple drivers for the same hardware is a bit > > > > > strange to begin with, but that's another issue entirely. > > > > > > > > If two drivers are loaded for the same device, there's no way for udev > > > > to tell the kernel which driver to use for a device, that I know of. > > > > > > /sys/bus/*/drivers/*/{bind,unbind} > > > > "bind" does not tell the driver core to "bind this device with this > > driver", it tells it to "bind this driver to whatever devices we match > > that aren't already bound". > > > > That doesn't solve my use case. > > I don't have any hardware with multiple drivers lying around, but I'm > fairly certain you can write the bus ID of a device into driver A's > unbind file and then follow that with a write of that bus ID into driver > B's bind file and get the effect that you want.
Certainly, that's the case. However, it should be possible to do this without letting the kernel bind a device to one driver, just to go back and unbind it, and bind to another driver.
> > > > > > Also, that just sounds very horrible to do. If you have udev/dbus events > > > > flying around for "device present", "device gone", "device present", > > > > then it could make for a very ugly user experience (think of programs to > > > > handle devices being started because of these events). > > > > > > So don't fire the events until after the final binding. > > > > It's still not a correct solution. If we want a specific driver to be > > bound to a specific device, userspace shouldn't have to jump through > > hoops to do it. It should be simple and clean. > > > > The suggestions you are giving require userspace to work around a > > deficiency in the kernel, by guessing the ordering requirements to > > satisfy what the user wants. In cases of hotplugging, it is also > > sometimes impossible to satisfy these requirements using the current > > scheme. > > Well, the kernel's deficiency is that there's multiple drivers for the > same hardware, not that userspace doesn't get first say in how hardware > is bound to drivers.
No, in a lot of cases, it's not a deficiency. Take the entire drivers/ata/pata_*.ko list. All of them match an IDE driver, however the pata driver most times does not support all the same PCI id's for the matching ide driver.
Also the other case I gave where there is an alsa driver and a media driver for the same chipset, is by design. It can't be helped. There actually is a case for wanting one driver or the other in the case of the exact same hardware, depending on the users desire. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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