From nobody Thu Jan 09 23:01:41 2025 X-Original-To: dev-commits-src-main@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4YTgK0207Bz5kDTp; Thu, 09 Jan 2025 23:01:56 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (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 4YTgJz4g5zz450j; Thu, 9 Jan 2025 23:01:55 +0000 (UTC) (envelope-from kostikbel@gmail.com) Authentication-Results: mx1.freebsd.org; none Received: from tom.home (kib@localhost [127.0.0.1] (may be forged)) by kib.kiev.ua (8.18.1/8.18.1) with ESMTP id 509N1fJ7095437; Fri, 10 Jan 2025 01:01:44 +0200 (EET) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua 509N1fJ7095437 Received: (from kostik@localhost) by tom.home (8.18.1/8.18.1/Submit) id 509N1fRK095436; Fri, 10 Jan 2025 01:01:41 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Fri, 10 Jan 2025 01:01:41 +0200 From: Konstantin Belousov To: John Baldwin Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: ccabc7c2e556 - main - DEVICE_IDENTIFY.9: Modernize description and use cases Message-ID: References: <202501092020.509KKt1U058876@gitrepo.freebsd.org> List-Id: Commit messages for the main branch of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-main List-Help: List-Post: List-Subscribe: List-Unsubscribe: X-BeenThere: dev-commits-src-main@freebsd.org Sender: owner-dev-commits-src-main@FreeBSD.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202501092020.509KKt1U058876@gitrepo.freebsd.org> X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FROM, NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on tom.home X-Rspamd-Queue-Id: 4YTgJz4g5zz450j X-Spamd-Bar: ---- X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:6939, ipnet:2001:470::/32, country:US] On Thu, Jan 09, 2025 at 08:20:55PM +0000, John Baldwin wrote: > The branch main has been updated by jhb: > > URL: https://cgit.FreeBSD.org/src/commit/?id=ccabc7c2e556ac0b14da9b682b706ccaf251c0fe > > commit ccabc7c2e556ac0b14da9b682b706ccaf251c0fe > Author: John Baldwin > AuthorDate: 2025-01-09 20:20:16 +0000 > Commit: John Baldwin > CommitDate: 2025-01-09 20:20:16 +0000 > > DEVICE_IDENTIFY.9: Modernize description and use cases > > Mention adding devices based on firmware tables and software-only > pseudo-devices as use cases for identify methods as those are more > common than reading random I/O ports to identify a legacy ISA device. > > Describe how device_find_chid can be used to avoid duplicates. While > here, explicitly note that devices added in identify methods typically > use a fixed device name. > > Trim the cross-references a bit. > > Reviewed by: ziaee, imp > Differential Revision: https://reviews.freebsd.org/D48367 > --- > share/man/man9/DEVICE_IDENTIFY.9 | 52 +++++++++++++++++++--------------------- > 1 file changed, 25 insertions(+), 27 deletions(-) > > diff --git a/share/man/man9/DEVICE_IDENTIFY.9 b/share/man/man9/DEVICE_IDENTIFY.9 > index d75c1a91ce4a..b10d94143050 100644 > --- a/share/man/man9/DEVICE_IDENTIFY.9 > +++ b/share/man/man9/DEVICE_IDENTIFY.9 > @@ -26,44 +26,46 @@ > .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF > .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. > .\" > -.Dd January 15, 2017 > +.Dd January 9, 2025 > .Dt DEVICE_IDENTIFY 9 > .Os > .Sh NAME > .Nm DEVICE_IDENTIFY > -.Nd identify a device, register it > +.Nd identify new child devices and register them > .Sh SYNOPSIS > .In sys/param.h > .In sys/bus.h > .Ft void > .Fn DEVICE_IDENTIFY "driver_t *driver" "device_t parent" So what is the 'parent' for driver which creates devices based on the firmware tables? > .Sh DESCRIPTION > -The identify function for a device is only needed for devices on buses > -that cannot identify their children independently, e.g.\& the ISA bus. > -It is used to recognize the device (usually done by accessing non-ambiguous > -registers in the hardware) and to tell the kernel about it and thus > -creating a new device instance. > +The identify method of a device driver is used to add devices that cannot be > +enumerated by the standard method on a bus device. > +Devices can be enumerated in various ways including accessing non-ambiguous > +device registers and parsing firmware tables. > +Software-only pseudo devices are also often enumerated via identify methods. > .Pp > +For each newly identified device, > +a new device instance should be created by invoking the > .Xr BUS_ADD_CHILD 9 > -is used to register the device as a child of the bus. > -The device's resources (such as IRQ and I/O ports) are registered > -with the kernel by calling > -.Fn bus_set_resource > -for each resource (refer to > +method. > +If the identify method is able to discover other properties about the new > +device, those should also be set. > +For example, device resources should be added to the device by calling > .Xr bus_set_resource 9 > -for more information). > +for each resource. > .Pp > -Since the device tree and the device driver tree are disjoint, the > -.Fn DEVICE_IDENTIFY > -routine needs to take this into account. > -If you load and unload your device driver that has the identify > -routine, the child node has the potential for adding the same node > -multiple times unless specific measure are taken to preclude that > -possibility. > +An identify method might be invoked multiple times. > +If a device driver is unloaded and loaded, > +the identify method will be called a second time after being reloaded. > +As a result, the identify method should avoid duplicate devices. > +Devices added by identify methods typically use a fixed device name > +in which case > +.Xr device_find_child 9 > +can be used to detect existing devices. > .Sh EXAMPLES > The following pseudo-code shows an example of a function that > probes for a piece of hardware and registers it and its resource > -(an I/O port) with the kernel. > +(an I/O port) with the parent bus device. > .Bd -literal > void > foo_identify(driver_t *driver, device_t parent) > @@ -72,7 +74,7 @@ foo_identify(driver_t *driver, device_t parent) > > retrieve_device_information; > if (devices matches one of your supported devices && > - not already in device tree) { > + device_get_child(parent, "foo", DEVICE_UNIT_ANY) == NULL) { > child = BUS_ADD_CHILD(parent, 0, "foo", DEVICE_UNIT_ANY); > bus_set_resource(child, SYS_RES_IOPORT, 0, FOO_IOADDR, 1); > } > @@ -82,11 +84,7 @@ foo_identify(driver_t *driver, device_t parent) > .Xr BUS_ADD_CHILD 9 , > .Xr bus_set_resource 9 , > .Xr device 9 , > -.Xr device_add_child 9 , > -.Xr DEVICE_ATTACH 9 , > -.Xr DEVICE_DETACH 9 , > -.Xr DEVICE_PROBE 9 , > -.Xr DEVICE_SHUTDOWN 9 > +.Xr device_find_child 9 > .Sh AUTHORS > This manual page was written by > .An Alexander Langer Aq Mt alex@FreeBSD.org .