From owner-freebsd-arm@freebsd.org Thu Aug 20 06:07:52 2020 Return-Path: Delivered-To: freebsd-arm@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 7A2703B17FA for ; Thu, 20 Aug 2020 06:07:52 +0000 (UTC) (envelope-from mishin@mh.net.ru) Received: from frog.mh.net.ru (mh.balakovo.san.ru [88.147.158.22]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4BXDhk3Wh9z3fCm for ; Thu, 20 Aug 2020 06:07:48 +0000 (UTC) (envelope-from mishin@mh.net.ru) Received: from webmail.mh.net.ru (mouse.home [192.168.5.6]) by frog.mh.net.ru (Postfix) with ESMTPSA id 61351AC6F9 for ; Thu, 20 Aug 2020 10:07:39 +0400 (+04) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Thu, 20 Aug 2020 10:07:38 +0400 From: Alexander Mishin To: freebsd-arm@freebsd.org Subject: Re: Kmod driver at iicbus. attach() and config_intrhook(9) 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> User-Agent: Roundcube Webmail/1.4.2 Message-ID: X-Sender: mishin@mh.net.ru X-Rspamd-Queue-Id: 4BXDhk3Wh9z3fCm X-Spamd-Bar: ++ Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=mh.net.ru (policy=none); spf=fail (mx1.freebsd.org: domain of mishin@mh.net.ru does not designate 88.147.158.22 as permitted sender) smtp.mailfrom=mishin@mh.net.ru X-Spamd-Result: default: False [2.18 / 15.00]; RCVD_TLS_ALL(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_SPF_FAIL(1.00)[-all]; MID_RHS_MATCH_FROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; NEURAL_SPAM_SHORT(0.56)[0.563]; MIME_GOOD(-0.10)[text/plain]; TO_DN_NONE(0.00)[]; PREVIOUSLY_DELIVERED(0.00)[freebsd-arm@freebsd.org]; NEURAL_SPAM_MEDIUM(0.61)[0.613]; RCPT_COUNT_ONE(0.00)[1]; ARC_NA(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:12389, ipnet:88.147.128.0/17, country:RU]; RCVD_COUNT_TWO(0.00)[2]; MAILMAN_DEST(0.00)[freebsd-arm]; DMARC_POLICY_SOFTFAIL(0.10)[mh.net.ru : No valid SPF, No valid DKIM,none] X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: "Porting FreeBSD to ARM processors." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 20 Aug 2020 06:07:52 -0000 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.