Date: Tue, 24 Jan 2012 15:53:41 +0200 From: Aleksandr Rybalko <ray@dlink.ua> To: Oleksandr Tymoshenko <gonzo@bluezbox.com> Cc: Ben Gray <ben.r.gray@gmail.com>, freebsd-arch@freebsd.org Subject: Re: Extending sys/dev/mii Message-ID: <20120124155341.84a000f5.ray@dlink.ua> In-Reply-To: <EDEACD17-6B1A-4F80-B20B-84ADB559092E@bluezbox.com> References: <8D025847-4BE4-4B2C-87D7-97E72CC9D325@lassitu.de> <20120104215930.GM90831@alchemy.franken.de> <47ABA638-7E08-4350-A03C-3D4A23BF2D7E@lassitu.de> <1763C3FF-1EA0-4DC0-891D-63816EBF4A04@lassitu.de> <20120106182756.GA88161@alchemy.franken.de> <95372FB3-406F-46C2-8684-4FDB672D9FCF@lassitu.de> <20120106214741.GB88161@alchemy.franken.de> <F60B2B70-049F-4497-BBA8-3C421088C1EA@lassitu.de> <20120108130039.GG88161@alchemy.franken.de> <23477898-8D85-498C-8E30-192810BD68A8@lassitu.de> <20120111193738.GB44286@alchemy.franken.de> <66DDA0A2-F878-43FF-8824-54868F493B18@lassitu.de> <8EF24110-C985-400F-ADDF-B1D63C4E304B@bsdimp.com> <4F1A3B58.7040001@freebsd.org> <EDEACD17-6B1A-4F80-B20B-84ADB559092E@bluezbox.com>
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On Mon, 23 Jan 2012 23:45:29 -0800
Oleksandr Tymoshenko <gonzo@bluezbox.com> wrote:
>>
>> On 2012-01-20, at 8:13 PM, Oleksandr Tymoshenko wrote:
>>
>> > On 20/01/2012 5:43 PM, Warner Losh wrote:
>> >>
>> >> On Jan 20, 2012, at 5:08 PM, Stefan Bethke wrote:
>> >>> The second problem is that there's currently no way to express a
>> >>> dependency between two devices other than a parent-child
>> >>> relationship. I would be interested to learn why this appears
>> >>> to be so uncommon that I could not find any discussion of such a
>> >>> feature. Has it really never before come up?
>> >>
>> >> Sure there is: you can do it by name. I wrote a driver that
>> >> attached to the ISA bus, but also needed to talk to the ppbus
>> >> that was attached to the printer. My solution was to have a
>> >> post-attach name-lookup so that it could then call methods on the
>> >> other driver's device_t. I wonder why we can't do that here?
>> >
>> > I've been thinking about it recently in regard to GPIO
>> > subsystem. And the same issue appeared during OMAP code import:
>> > there are at least two subsystems that are used by the rest of the
>> > drivers. Ben's suggested following solution: define kobj interface
>> > if_SUBSYTEM.m and then provide API call in form:
>> >
>> > int omap_prcm_clk_enable(clk_ident_t clk)
>> > {
>> > device_t prcm_dev;
>> >
>> > prcm_dev = devclass_get_device(devclass_find("omap_prcm"),
>> > 0); if (prcm_dev == NULL) {
>> > printf("Error: failed to get the PRCM device\n");
>> > return (EINVAL);
>> > }
>> >
>> > return OMAP_PRCM_CLK_ENABLE(prcm_dev, clk);
>> > }
>> >
>> > So it might make sense to create some kind of upper-level API for
>> > defining this kind of subsystems' APIs since every implementation
>> > would duplicate a lot of code: look for instance of specific
>> > devclass, check if it exists. Not sure how to do it at the moment
>> > though.
>>
>>
>> I tinkered a little bit with this idea and here is what I've come up
>> with so far:
>>
>> http://people.freebsd.org/~gonzo/patches/horizontal-api.diff
>>
>> this patch adds one more available declaration to .m files: APIMETHOD
>> In addition to usual kobj method declaration one more function is
>> generated. This function gets first device in devclass with the same
>> name as declared interface and uses it as object for respective
>> method call.
>>
>> Also if there is at least one APIMETHOD in interface one more
>> function called XXXX_available() is generated. It returns 1 if there
>> is device of required devclass.
>>
>> Usage example:
>> int maxpin;
>>
>> printf("GPIO available: %d\n", gpio_available());
>> if (gpio_available()) {
>> gpio_pin_max(&maxpin);
>> printf("GPIO pins: %d\n", maxpin);
>> }
>>
>> Possible improvements: instead of using devclass for identifying
>> kobj, create way for device to explicitly register/deregister as an
>> API "provider".
If I understand patch correct, it will search for device every "API"
call. Is it good?
>>
>>
>> Comments, ideas?_______________________________________________
>> freebsd-arch@freebsd.org mailing list
>> http://lists.freebsd.org/mailman/listinfo/freebsd-arch
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--
Alexandr Rybalko <ray@dlink.ua>
aka Alex RAY <ray@ddteam.net>
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