From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Subject: [v3,1/5] ACPI / bus: Return error code from __acpi_match_device() in one case From: Andy Shevchenko Message-Id: <1518105548.22495.201.camel@linux.intel.com> Date: Thu, 08 Feb 2018 17:59:08 +0200 To: "Rafael J. Wysocki" Cc: dmaengine , "Rafael J . Wysocki" , ACPI Devel Maling List , Mika Westerberg , Sinan Kaya , Sakari Ailus , Vinod Koul List-ID: T24gVGh1LCAyMDE4LTAyLTA4IGF0IDE2OjQ4ICswMTAwLCBSYWZhZWwgSi4gV3lzb2NraSB3cm90 ZToKPiBPbiBUaHUsIEZlYiA4LCAyMDE4IGF0IDQ6NDQgUE0sIEFuZHkgU2hldmNoZW5rbwo+IDxh bmRyaXkuc2hldmNoZW5rb0BsaW51eC5pbnRlbC5jb20+IHdyb3RlOgo+ID4gT24gVGh1LCAyMDE4 LTAyLTA4IGF0IDE2OjE0ICswMTAwLCBSYWZhZWwgSi4gV3lzb2NraSB3cm90ZToKPiA+ID4gCgo+ ID4gCj4gPiA+IEFsc28gdGhlIHJldHVybiB2YWx1ZSBoZXJlIG1lYW5zICJzdWNjZXNzIiwgc28g d2h5IGlzIGFuIGVycm9yIHRoZQo+ID4gPiByaWdodCBjaG9pY2U/Cj4gPiAKPiA+IEJlY2F1c2Ug d2UgbmVlZCB0byByZXR1cm4gc29tZXRoaW5nIHdoaWNoIGlzIG5vdCBOVUxMLiBOYXR1cmFsbHkK PiA+IGZlZWxzCj4gPiB0aGUgZXJyb3IgY29kZSwgZXNwLiBFTk9EQVRBLCBpcyBxdWl0ZSBzdWl0 YWJsZS4gV2UgaW5kZWVkIGhhdmUgbm8KPiA+IGRhdGEKPiA+IGluIHRoaXMgY2FzZSwgYW5kIGl0 J3Mgbm90IGEgTlVMTCBjYXNlIChub3QgZm91bmQgLyBub3QgbWF0Y2gpIOKAlCB3ZQo+ID4gaGF2 ZQo+ID4gYSBtYXRjaC4KPiAKPiBCdXQgdGhpcyBpcyBhbiBlcnJvciBjb2RlIHRoYXQgbWVhbnMg InN1Y2Nlc3MiLiAgTWF5IEkgY2FsbCBpdCByYXRoZXIKPiBjb25mdXNpbmc/CgpUaGlzIGZ1bmN0 aW9uIEFGQUlDUyBkb2VzIHR3byB0aGluZ3MgYXQgb25jZToKLSBtYXRjaGVzIGRldmljZSBhZ2Fp bnN0IElECi0gcmV0dXJucyBtYXRjaGVkIElEIGVudHJ5IGluIHRoZSB0YWJsZQoKUmV0dXJuIHZh bHVlIGNvbWJpbmVzIHRob3NlIHR3byBpbnRvIGFjdHVhbGx5IHRlcm5hcnkgb3B0aW9uOgotIG5v IG1hdGNoCi0gbWF0Y2ggd2l0aCBJRAotIG1hdGNoIHdpdGhvdXQgSUQKCj4gPiA+IE92ZXJhbGws IHRoaXMgcmVhbGx5IGxvb2tzIGxpa2UgYSBwcmVwYXJhdGlvbiBmb3IgYSBmdXR1cmUgcGF0Y2gs Cj4gPiA+IHNvCj4gPiA+IHdoeSBub3QganVzdCBzYXkgdGhhdCBzdHJhaWdodCBhd2F5IGluIHRo ZSBjaGFuZ2Vsb2c/Cj4gPiAKPiA+IEl0J3Mgbm90IF9qdXN0XyBhIHByZXBhcmF0aW9uLCBpdCBt aXRpZ2F0ZXMgdGhlIHRyaWNrIHVzZWQgaW4KPiA+IG1lbnRpb25lZAo+ID4gYnkgRml4ZXMgdGFn IGNvbW1pdC4KPiA+IAo+ID4gSSB3b3VsZCByYXRoZXIgdXBkYXRlIGNvbW1lbnQgaGVyZSwgYW5k IGFkZCBleHBsYW5hdGlvbiB0byB0aGUKPiA+IGNvbW1pdAo+ID4gbWVzc2FnZSB0byBiZSBzdXJl IGl0IGNvdmVycyB0cmlja3MgbWl0aWdhdGlvbiBhbmQgcHJlcGFyYXRpb24KPiA+IHB1cnBvc2Vz Lgo+IAo+IFRoaXMgaXMgbm90IG1pdGlnYXRpb24sIHNvcnJ5LiAgSXQganVzdCByZXBsYWNlcyBv bmUgcG9zc2libHkKPiBjb25mdXNpbmcgdGhpbmcgd2l0aCBhbm90aGVyLgoKSSB3b3VsZCBhZ3Jl ZSBoZXJlLi4uCgo+IFRoZSBjb2RlIGFzIGlzIHdvcmtzIGFzIEkgc2FpZCBhbmQgdGhpcyBwYXRj aCBkb2Vzbid0IG1ha2UgaXQgYW55Cj4gYmV0dGVyIGFzIGZhciBhcyBJJ20gY29uY2VybmVkLgoK Li4uYnV0IG5vdCBoZXJlLiBJbnN0ZWFkIG9mIHJldHVybmluZyBwb2ludGVyIHRvICpzb21ldGhp bmcqIChmcm9tCmNhbGxlciBwb2ludCBvZiB2aWV3KSwgd2UgZXhwbGljaXRseSB0ZWxsIGNhbGxl ciB3aGF0IG9mIHRoZSBhYm92ZQpoYXBwZW5lZC4gV2UgZG9uJ3QgcmVseSBvbiB0aGUgb3JnYW5p emF0aW9uICBvZiBJRCB0YWJsZSBvciBpdHMgbGlmZQp0aW1lICh0aG91Z2ggaXQncyBmb3JldmVy KS4KCkkgY2FuIHNheSB0aGF0IGlzICpzbGlnaHRseSogYmV0dGVyLiBCdXQgYWdyZWUgdGhhdCBp cyBub3QgY2xlYW5lc3QKc29sdXRpb24gSSBjYW4gY29tZSB1cCB3aXRoLgoKSSdtIGFsbCBlYXJz IG9uIG90aGVyIHBvc3NpYmlsaXRpZXMgaG93IHRvIGdldCByaWQgb2YgdGhhdCB0cmljay4K From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Subject: Re: [PATCH v3 1/5] ACPI / bus: Return error code from __acpi_match_device() in one case Date: Thu, 08 Feb 2018 17:59:08 +0200 Message-ID: <1518105548.22495.201.camel@linux.intel.com> References: <20180207145610.88434-1-andriy.shevchenko@linux.intel.com> <1518104647.22495.195.camel@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Return-path: Received: from mga03.intel.com ([134.134.136.65]:20944 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752422AbeBHP7M (ORCPT ); Thu, 8 Feb 2018 10:59:12 -0500 In-Reply-To: Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: "Rafael J. Wysocki" Cc: dmaengine , "Rafael J . Wysocki" , ACPI Devel Maling List , Mika Westerberg , Sinan Kaya , Sakari Ailus , Vinod Koul On Thu, 2018-02-08 at 16:48 +0100, Rafael J. Wysocki wrote: > On Thu, Feb 8, 2018 at 4:44 PM, Andy Shevchenko > wrote: > > On Thu, 2018-02-08 at 16:14 +0100, Rafael J. Wysocki wrote: > > > > > > > > Also the return value here means "success", so why is an error the > > > right choice? > > > > Because we need to return something which is not NULL. Naturally > > feels > > the error code, esp. ENODATA, is quite suitable. We indeed have no > > data > > in this case, and it's not a NULL case (not found / not match) — we > > have > > a match. > > But this is an error code that means "success". May I call it rather > confusing? This function AFAICS does two things at once: - matches device against ID - returns matched ID entry in the table Return value combines those two into actually ternary option: - no match - match with ID - match without ID > > > Overall, this really looks like a preparation for a future patch, > > > so > > > why not just say that straight away in the changelog? > > > > It's not _just_ a preparation, it mitigates the trick used in > > mentioned > > by Fixes tag commit. > > > > I would rather update comment here, and add explanation to the > > commit > > message to be sure it covers tricks mitigation and preparation > > purposes. > > This is not mitigation, sorry. It just replaces one possibly > confusing thing with another. I would agree here... > The code as is works as I said and this patch doesn't make it any > better as far as I'm concerned. ...but not here. Instead of returning pointer to *something* (from caller point of view), we explicitly tell caller what of the above happened. We don't rely on the organization of ID table or its life time (though it's forever). I can say that is *slightly* better. But agree that is not cleanest solution I can come up with. I'm all ears on other possibilities how to get rid of that trick. -- Andy Shevchenko Intel Finland Oy