Date: Mon, 5 Jan 2015 12:16:50 -0800 From: Adrian Chadd <adrian@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: "freebsd-arch@freebsd.org" <arch@freebsd.org> Subject: Re: devctl(8): A device control utility Message-ID: <CAJ-VmokUvmtVi1FNcGnnVPTWtThn4j3bKdEg_%2Bb2%2Bn8Q-FZp7w@mail.gmail.com> In-Reply-To: <3200196.9ZgXApgRdA@ralph.baldwin.cx> References: <3200196.9ZgXApgRdA@ralph.baldwin.cx>
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Hi, This looks good to me. I'm sure there will be fallout (like hps@ comment about sync'ing with other attach/detach things in USB) but I think this is fine as-is and will be useful for finding bugs in various attach/detach paths. -adrian On 5 January 2015 at 12:01, John Baldwin <jhb@freebsd.org> wrote: > For a long time I've wanted a way to administratively manipulate the state of > new-bus devices from userland. I think the first use case I wanted was a way > to power off the sound controller (and anything else I wasn't using) on my > first laptop (a Dell Inspiron 5000e I got back in 2000). Similarly, it would > be nice to have a way to handle "ejectable" devices (ACPI has a provision for > this, and said laptop had _EJx methods to allow one to swap a CD drive out for > a battery in a bay while the laptop was in S3). There are some other use > cases that would also be nice such as detaching a driver from a PCI device to > decide at runtime that it should be passed through to a bhyve guest (and > possibly undoing that to allow a host driver to take it back over). Forcing a > rescan of a PCI device can be useful if you are using an FPGA and would like > to alter BAR layout/sizes without having to reboot the OS. A way to force > resets at runtime might also be useful (e.g. a FLR for a PCI device). A few > weeks ago I finally sat down and started on an implementation. It can be > found here: > > https://github.com/bsdjhb/freebsd/compare/devctl > > Sample commands look like: > > % devctl disable virtio_pci2 > > # detaches the driver, but leaves the device's name intact similar to > # specifying hint.virtio_pci.2.disabled=1 at boot > > % devctl enable virtio_pci2 > > # enables a disabled device, including attaching it > > % devctl detach uart1 > > # does a full detach, which means the device is now unnamed > > % devctl attach \_SB_.PCI0.LPC.UAR1 > > # attaches an unattached device. A provision is made for recognizing > # device addresses via an EVENTHANDLER hook that a bus driver can > # install. Currently ACPI handles and pci selectors (ala pciconf) > # are recognized via hooks in the ACPI and PCI bus drivers. > > % devctl set driver foo0 bar > > # forces the 'foo0' device to use the 'bar' device class and thus > # only attach to a driver named 'bar' (assuming that 'bar' will > # probe it, this doesn't override device_probe). With some changes > # to ppt.c, this would allow one to do 'devctl set driver foo0 ppt' > # to detach a host driver and mark a device for PCI passthrough at > # runtime. I have not yet implemented a "clear driver" to reset > # back to an empty device class. > > The current version also includes 'suspend' and 'resume' commands which > use bus_suspend_child() (recently added by Justin Hibbits) to suspend > (and possibly power down) individual devices. > > Implementation notes: > > For the kernel <-> userland interface, I chose to use ioctls. The ioctls > use a 'struct devreq' structure that is modeled on 'struct ifreq' used > for network interface ioctls in that there are a set of common fields and > a union of request-specific fields. > > I would have liked to reuse /dev/devctl for this, but it is a single > purpose device intended for use by devd. If I had my druthers, I would > probably like to rename /dev/devctl to /dev/devevents or /dev/devnotify > or some such and create a new /dev/devctl for these control ioctls. Instead > what I've done for now is create a /dev/devctl2 for the new ioctls. > > There is a thin library (libdevctl) that wraps the /dev/devctl2 ioctls and > provides methods like devctl_detach(), etc. The thin library even has a > manpage already. > > The devctl(8) utility is then a thin wrapper around libdevctl (and does not > yet have a manpage). > > Do folks have any feedback? > > -- > John Baldwin > _______________________________________________ > freebsd-arch@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-arch > To unsubscribe, send any mail to "freebsd-arch-unsubscribe@freebsd.org"
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