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[83.31.7.43]) by smtp.gmail.com with ESMTPSA id w202-v6sm1572631lff.17.2018.09.21.15.11.30 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 21 Sep 2018 15:11:31 -0700 (PDT) Subject: Re: [PATCH v12 1/2] leds: core: Introduce LED pattern trigger To: Pavel Machek Cc: Baolin Wang , rteysseyre@gmail.com, Bjorn Andersson , Mark Brown , Linus Walleij , Linux LED Subsystem , LKML References: <67ebebf02edd6d8ee42a13b139733e9cc680ea86.1536631975.git.baolin.wang@linaro.org> <324778a9-a32c-ae6e-337a-39845f214bfc@gmail.com> <20180921211758.GC18062@amd> From: Jacek Anaszewski Message-ID: Date: Sat, 22 Sep 2018 00:11:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180921211758.GC18062@amd> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/21/2018 11:17 PM, Pavel Machek wrote: > On Fri 2018-09-21 22:59:40, Jacek Anaszewski wrote: >> Hi Baolin, >> >> On 09/21/2018 05:31 AM, Baolin Wang wrote: >>> Hi Jacek and Pavel, >>> >>> On 11 September 2018 at 10:47, Baolin Wang wrote: >>>> This patch adds one new led trigger that LED device can configure >>>> the software or hardware pattern and trigger it. >>>> >>>> Consumers can write 'pattern' file to enable the software pattern >>>> which alters the brightness for the specified duration with one >>>> software timer. >>>> >>>> Moreover consumers can write 'hw_pattern' file to enable the hardware >>>> pattern for some LED controllers which can autonomously control >>>> brightness over time, according to some preprogrammed hardware >>>> patterns. >>>> >>>> Signed-off-by: Raphael Teysseyre >>>> Signed-off-by: Baolin Wang > >>> Do you have any comments for the v12 patch set? Thanks. >> >> We will probably have to remove hw_pattern from ledtrig-pattern >> since we are unable to come up with generic interface for it. >> Unless thread [0] will end up with some brilliant ideas. So far >> we're waiting for Pavel's reply. >> >> [0] https://lkml.org/lkml/2018/9/13/1216 > > To paint a picture: > > brightness > > rise hold lower hold down > ^ XXXXXXXXXXXXXXX > | X XX > | X XX > | X XXXXXXXXXXXXXXXXXXXXXXXXXX > +-------------------------------------------------------> time > > This is what Baolin's hardware can do, right? > > This is also what pattern trigger can do, right? > > So all we need to do is match the two interfaces, so that hw_pattern > returns -EINVAL on patterns hardware can not actually do. > > I believe I described code to do that in [0] above. You said that we should get the same effect by writing the same series of tuples to either pattern or hw_pattern file. Below command consists of four tuples (marked with brackets to highlight), and it will activate breathing mode in Baolin's hw_pattern: "[0 rise_duration] [brightness high_duration] [brightness fall_duration] [0 low_duration]" Now, I can't see how these four tuples could force the software fallback to produce breathing effect you depicted. -- Best regards, Jacek Anaszewski