Date: Wed, 19 Aug 2020 14:15:51 +0400 From: Alexander Mishin <mishin@mh.net.ru> To: Oleksandr Tymoshenko <gonzo@bluezbox.com> Subject: Re: Kmod driver at iicbus. attach() and config_intrhook(9) Message-ID: <cb1b1a670c4b624318fc090aacb014c3@mh.net.ru> In-Reply-To: <20200819072409.GA59949@bluezbox.com> References: <7fabb65d99aaa74775c1daa91bffb873@mh.net.ru> <3249fa7e-554a-83ef-57b2-7c38aa0b4591@FreeBSD.org> <20200819072409.GA59949@bluezbox.com>
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Thanks for your answers, especially for "...controllers use interrupts to get notified about...". It helped to understand. Yes, I need it as I check on attach() if the device connected. Everything was fine while I was loading the driver into an already running system, but as soon as I loaded the driver at boot time, I saw that its sysctl variables was only half filled (no result nor calculated values). config_intrhook_oneshot() solved this issue. Thanks once more Oleksandr Tymoshenko писал 2020-08-19 11:24: > 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.
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