Re: [PATCH 4/5] driver core: inhibit automatic driver binding on reserved devices

Andy Shevchenko
2021-10-25T12:58:55Z

On Mon, Oct 25, 2021 at 06:44:26AM -0500, Patrick Williams wrote:
> On Mon, Oct 25, 2021 at 08:15:41AM +0200, Greg Kroah-Hartman wrote:
> > On Mon, Oct 25, 2021 at 12:38:08AM -0500, Frank Rowand wrote:
> > > On 10/23/21 3:56 AM, Greg Kroah-Hartman wrote:
>
> > We have the bind/unbind ability today, from userspace, that can control
> > this. Why not just have Linux grab the device when it boots, and then
> > when userspace wants to "give the device up", it writes to "unbind" in
> > sysfs, and then when all is done, it writes to the "bind" file and then
> > Linux takes back over.
> >
> > Unless for some reason Linux should _not_ grab the device when booting,
> > then things get messier, as we have seen in this thread.
>
> This is probably more typical on a BMC than atypical. The systems often require
> the BMC (running Linux) to be able to reboot independently from the managed host
> (running anything). In the example Zev gave, the BMC rebooting would rip away
> the BIOS chip from the running host.
>
> The BMC almost always needs to come up in a "I don't know what could possibly be
> going on in the system" state and re-discover where the system was left off.

Isn't it an architectural issue then?

--
With Best Regards,
Andy Shevchenko