Date: Thu, 20 Aug 2020 10:07:38 +0400 From: Alexander Mishin <mishin@mh.net.ru> To: freebsd-arm@freebsd.org Subject: Re: Kmod driver at iicbus. attach() and config_intrhook(9) Message-ID: <d603cf3b852d5e18fa5faa9066f643a3@mh.net.ru> In-Reply-To: <05145b71692af74b103bb226a2e93a15e1e851cb.camel@freebsd.org> References: <7fabb65d99aaa74775c1daa91bffb873@mh.net.ru> <3249fa7e-554a-83ef-57b2-7c38aa0b4591@FreeBSD.org> <20200819072409.GA59949@bluezbox.com> <05145b71692af74b103bb226a2e93a15e1e851cb.camel@freebsd.org>
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Ian Lepore писал 2020-08-19 19:39: > On Wed, 2020-08-19 at 00:24 -0700, Oleksandr Tymoshenko wrote: >> Andriy Gapon (avg@FreeBSD.org) wrote: >> > On 18/08/2020 22:05, Alexander Mishin wrote: >> > > Hi >> > > ... >> > > But I see that some other devices (from /usr/src/sys/dev) uses >> > > CONFIG_INTRHOOK(9) >> > > on attach() for initialize themselfs. >> > > I wonder if I need this too? ... >> > >> > This is usually needed when a driver needs to talk to its device >> > while >> > attaching. E.g., to set some initial configuration or to confirm >> > device's >> > identity, etc. >> >> To extend Andriy's explanation a bit: all these operations may >> perform >> I2C transfers and most I2C controllers use interrupts to get notified >> about tranfer status change (finished, error, etc...). There is no >> guarantee that when driver's attach method is called interrupts are >> globally enabled. What would happen in this case is: I2C controller >> is going to initiate I2C operation and wait for an interrupt that's >> never going to be delivered. CONFIG_INTRHOOK is a solution for this >> problem, if your attach method requires interrupts - just split it >> in two parts and postpone running interrupt-dependent part until >> after >> interrupts are globally enabled. >> > > A note about all this: It should never be necessary for an i2c slave > device driver to do this. The reason it's needed is because many i2c > controller drivers attach the iicbus from their attach() routine even > though they can't actually do i2c IO until interrupts are available. > It is these controller drivers that should have the intrhook logic to > not call bus_generic_attach() until interrupts are available if they > can't do IO until interrupts are available. > > It has long been my goal to fix all our i2c controller drivers to > behave correctly, so that i2c slave device drivers don't all need the > intrhook logic. But somehow I never get around to it. > > -- Ian I think, it would be helpful, as it would be possible to return an error on early stage, from attach(), if there is no connection with the configured device.
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