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[85.228.174.190]) by smtp.gmail.com with ESMTPSA id w6sm510268ljw.11.2020.06.30.01.38.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jun 2020 01:38:13 -0700 (PDT) Received: from johan by xi.terra with local (Exim 4.93.0.4) (envelope-from ) id 1jqBmM-0001nh-86; Tue, 30 Jun 2020 10:38:11 +0200 Date: Tue, 30 Jun 2020 10:38:10 +0200 From: Johan Hovold To: Lee Jones Subject: Re: [PATCH 2/5] mfd: lm3533-ctrlbank: Cap BRIGHTNESS_MAX to 127 since API uses u8 as carrier Message-ID: <20200630083810.GY3334@localhost> References: <20200629123215.1014747-1-lee.jones@linaro.org> <20200629123215.1014747-3-lee.jones@linaro.org> <20200629125102.GT3334@localhost> <20200629132506.GJ177734@dell> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200629132506.GJ177734@dell> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Johan Hovold , Johan Hovold , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org T24gTW9uLCBKdW4gMjksIDIwMjAgYXQgMDI6MjU6MDZQTSArMDEwMCwgTGVlIEpvbmVzIHdyb3Rl Ogo+IE9uIE1vbiwgMjkgSnVuIDIwMjAsIEpvaGFuIEhvdm9sZCB3cm90ZToKPiAKPiA+IE9uIE1v biwgSnVuIDI5LCAyMDIwIGF0IDAxOjMyOjEyUE0gKzAxMDAsIExlZSBKb25lcyB3cm90ZToKPiA+ ID4gU2luY2UgaXRzIGNvbmNlcHRpb24gaW4gMjAxMiBicmlnaHRuZXNzIGhhcyBiZWVuIGFydGlm aWNpYWxseSBjYXBwZWQKPiA+ID4gYXQgMTI3IHNpbmNlIHRoZSB2YXJpYWJsZSBjYXJyeWluZyB0 aGUgdmFsdWUgaXMgdTguICBXZSBjb3VsZCBnbyB0bwo+ID4gPiB0aGUgdHJvdWJsZSBvZiBjaGFu Z2luZyB0aGUgd2hvbGUgQVBJIChjcm9zc2luZyAzIGRpZmZlcmVudCBzdWJzeXN0ZW1zKSwKPiA+ ID4gYnV0IGNsZWFybHkgdGhpcyBoYXNuJ3QgYm90aGVyZWQgYW55b25lIGluIHRoZSBiZXN0IHBh cnQgb2YgYSBkZWNhZGUuCj4gPiA+IAo+ID4gPiBTaW1wbHksIGNhcCBCUklHSFRORVNTX01BWCB0 byAxMjcgaW5zdGVhZCAoZm9yIG5vdyBhdCBsZWFzdCkuCj4gPiAKPiA+IEhtbS4gVGhpcyBwYXRj aCBpcyBjbGVhcmx5IGJyb2tlbiBhbmQgd291bGQgY29udHJhcnkgdG8gdGhlIGNsYWltIGJlCj4g PiBpbnRyb2R1Y2luZyBhbiBhcnRpZmljaWFsIGNhcCBhdCBoYWxmIGJyaWdodG5lc3MuIHU4IGNh biBob2xkIHRoZSBtYXgKPiA+IGJyaWdodG5lc3MgdmFsdWUgMjU1IGp1c3QgZmluZS4KPiAKPiBZ ZXMsIG9mIGNvdXJzZSBpdCBjYW4uICBTZW5pb3IgbW9tZW50IG9uIG15IGFjY291bnQuCj4gCj4g PiA+IEZpeGVzIHRoZSBmb2xsb3dpbmcgVz0xIHdhcm5pbmcocyk6Cj4gPiA+IAo+ID4gPiAgZHJp dmVycy9tZmQvbG0zNTMzLWN0cmxiYW5rLmM6IEluIGZ1bmN0aW9uIOKAmGxtMzUzM19jdHJsYmFu a19zZXRfYnJpZ2h0bmVzc+KAmToKPiA+ID4gIGRyaXZlcnMvbWZkL2xtMzUzMy1jdHJsYmFuay5j Ojk4OjEwOiB3YXJuaW5nOiBjb21wYXJpc29uIGlzIGFsd2F5cyBmYWxzZSBkdWUgdG8gbGltaXRl ZCByYW5nZSBvZiBkYXRhIHR5cGUgWy1XdHlwZS1saW1pdHNdCj4gPiA+ICA5OCB8IGlmICh2YWwg PiBMTTM1MzNfIyNfTkFNRSMjX01BWCkgfCBeCj4gPiA+ICBkcml2ZXJzL21mZC9sbTM1MzMtY3Ry bGJhbmsuYzoxMjU6MTogbm90ZTogaW4gZXhwYW5zaW9uIG9mIG1hY3JvIOKAmGxtMzUzM19jdHJs YmFua19zZXTigJkKPiA+ID4gIDEyNSB8IGxtMzUzM19jdHJsYmFua19zZXQoYnJpZ2h0bmVzcywg QlJJR0hUTkVTUyk7Cj4gPiA+ICB8IF5+fn5+fn5+fn5+fn5+fn5+fn4KPiA+IAo+ID4gVGhpcyB3 YXJuaW5nIGlzIGJlbmlnbi4gVGhlIHNhbWUgbWFjcm8gaXMgdXNlZCB0byBkZWZpbmVkIHR3byBm dW5jdGlvbgo+ID4gd2hlcmUgaW4gb25lIGNhc2UgdGhlIG1heCB2YWx1ZSBjb2luY2lkZXMgd2l0 aCBVOF9NQVggc28gdGhhdCB0aGUgc2FuaXR5Cj4gPiBjaGVjayBiZWNvbWVzIHJlZHVuZGFudC4K PiAKPiBBIGJlbmlnbiB3YXJuaW5nLCBhcyBtb3N0IFc9MSB3YXJuaW5ncyBhcmUsIGlzIHN0aWxs IGEgd2FybmluZy4KCk5vdCBldmVyeSB3YXJuaW5nIG5lZWRzIHRvIGJlIGFkZHJlc3NlZCwgdGhl cmUncyBhIHJlYXNvbiBzb21lIG9mIHRoZXNlCmFyZSBoaWRkZW4gYmVoaW5kIFc9MSBvciBoaWdo ZXIuCgo+IFNvIGhvdyBkbyB5b3UgcHJvcG9zZSB3ZSBmaXggaXQ/Cj4gCj4gSXMgMjU1IGEgdmFs aWQgYW5kIHVzZWQgYnJpZ2h0bmVzcyBsZXZlbD8KClllcy4KCj4gSWYgc28sIGhvdyBkbyB5b3Ug ZmVlbCBhYm91dDoKPiAKPiAgIC8qIEF2b2lkICdhbHdheXMgZmFsc2UnIGNoZWNrICcodTgpID4g MjU1JyAqLwo+ICAgaWYgKExNMzUzM18jI19OQU1FIyNfTUFYICE9IDB4ZmYgJiYgdmFsID4gTE0z NTMzXyMjX05BTUUjI19NQVgpCj4gICAgICAgICAgIHJldHVybiAtRUlOVkFMOyAgICAgICAgCgpJ J20gYWZyYWlkIHRoYXQncyBub3Qgc3VmZmljaWVudCB0byBzaHV0IHRoZSBjb21waWxlciB1cC4K CkknbGwgc2VuZCB5b3UgcGF0Y2ggZXhwYW5kaW5nIHRoZXNlIGFjY2Vzc29ycyBpbnN0ZWFkLiBI YXZpbmcgZXhwb3J0ZWQKZnVuY3Rpb25zIGltcGxlbWVudGVkIGJ5IG1hY3JvcyBpcyBwYXJ0aWN1 bGFybHkgbmljZSAoaGFyZCB0byBncmVwIGZvcgpldGMpLiBUaGVyZSBhcmUgYSBjb3VwbGUgb2Yg bW9yZSBzZXRzIG9mIGNvbnRyb2wtYmFuayByZWdpc3RlcnMgdGhhdApjb3VsZCBwb3RlbnRpYWxs eSBoYXZlIHNoYXJlZCB0aGUgaW1wbGVtZW50YXRpb24gYW5kIHdoaWNoIG1vdGl2YXRlZCB0aGUK dXNlIG9mIG1hY3JvcywgYnV0IGl0IGRvZXMgbm90IHNlZW0gdmVyeSBsaWtlbHkgdGhhdCB3ZSds bCBiZSBhZGRpbmcKdGhvc2UgYW55dGltZSBzb29uIGFueXdheS4KCkpvaGFuCgpfX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fXwpsaW51eC1hcm0ta2VybmVsIG1h aWxpbmcgbGlzdApsaW51eC1hcm0ta2VybmVsQGxpc3RzLmluZnJhZGVhZC5vcmcKaHR0cDovL2xp c3RzLmluZnJhZGVhZC5vcmcvbWFpbG1hbi9saXN0aW5mby9saW51eC1hcm0ta2VybmVsCg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 485E6C433E0 for ; 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[85.228.174.190]) by smtp.gmail.com with ESMTPSA id w6sm510268ljw.11.2020.06.30.01.38.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jun 2020 01:38:13 -0700 (PDT) Received: from johan by xi.terra with local (Exim 4.93.0.4) (envelope-from ) id 1jqBmM-0001nh-86; Tue, 30 Jun 2020 10:38:11 +0200 Date: Tue, 30 Jun 2020 10:38:10 +0200 From: Johan Hovold To: Lee Jones Cc: Johan Hovold , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Johan Hovold Subject: Re: [PATCH 2/5] mfd: lm3533-ctrlbank: Cap BRIGHTNESS_MAX to 127 since API uses u8 as carrier Message-ID: <20200630083810.GY3334@localhost> References: <20200629123215.1014747-1-lee.jones@linaro.org> <20200629123215.1014747-3-lee.jones@linaro.org> <20200629125102.GT3334@localhost> <20200629132506.GJ177734@dell> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200629132506.GJ177734@dell> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 29, 2020 at 02:25:06PM +0100, Lee Jones wrote: > On Mon, 29 Jun 2020, Johan Hovold wrote: > > > On Mon, Jun 29, 2020 at 01:32:12PM +0100, Lee Jones wrote: > > > Since its conception in 2012 brightness has been artificially capped > > > at 127 since the variable carrying the value is u8. We could go to > > > the trouble of changing the whole API (crossing 3 different subsystems), > > > but clearly this hasn't bothered anyone in the best part of a decade. > > > > > > Simply, cap BRIGHTNESS_MAX to 127 instead (for now at least). > > > > Hmm. This patch is clearly broken and would contrary to the claim be > > introducing an artificial cap at half brightness. u8 can hold the max > > brightness value 255 just fine. > > Yes, of course it can. Senior moment on my account. > > > > Fixes the following W=1 warning(s): > > > > > > drivers/mfd/lm3533-ctrlbank.c: In function ‘lm3533_ctrlbank_set_brightness’: > > > drivers/mfd/lm3533-ctrlbank.c:98:10: warning: comparison is always false due to limited range of data type [-Wtype-limits] > > > 98 | if (val > LM3533_##_NAME##_MAX) | ^ > > > drivers/mfd/lm3533-ctrlbank.c:125:1: note: in expansion of macro ‘lm3533_ctrlbank_set’ > > > 125 | lm3533_ctrlbank_set(brightness, BRIGHTNESS); > > > | ^~~~~~~~~~~~~~~~~~~ > > > > This warning is benign. The same macro is used to defined two function > > where in one case the max value coincides with U8_MAX so that the sanity > > check becomes redundant. > > A benign warning, as most W=1 warnings are, is still a warning. Not every warning needs to be addressed, there's a reason some of these are hidden behind W=1 or higher. > So how do you propose we fix it? > > Is 255 a valid and used brightness level? Yes. > If so, how do you feel about: > > /* Avoid 'always false' check '(u8) > 255' */ > if (LM3533_##_NAME##_MAX != 0xff && val > LM3533_##_NAME##_MAX) > return -EINVAL; I'm afraid that's not sufficient to shut the compiler up. I'll send you patch expanding these accessors instead. Having exported functions implemented by macros is particularly nice (hard to grep for etc). There are a couple of more sets of control-bank registers that could potentially have shared the implementation and which motivated the use of macros, but it does not seem very likely that we'll be adding those anytime soon anyway. Johan