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[104.188.17.28]) by smtp.gmail.com with ESMTPSA id d26-v6sm6684387pfl.159.2018.08.02.14.55.18 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 02 Aug 2018 14:55:18 -0700 (PDT) Date: Thu, 2 Aug 2018 14:53:40 -0700 From: Bjorn Andersson To: Jacek Anaszewski Cc: Baolin Wang , pavel@ucw.cz, rteysseyre@gmail.com, david@lechnology.com, broonie@kernel.org, linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] leds: core: Introduce LED pattern trigger Message-ID: <20180802215340.GP30024@minitux> References: <1bf9aed83d1756dd4f81590297ce7e0b9972bf85.1533112637.git.baolin.wang@linaro.org> <34c87589-ccaf-e541-7acb-efcf3bd306f6@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <34c87589-ccaf-e541-7acb-efcf3bd306f6@gmail.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 02 Aug 14:21 PDT 2018, Jacek Anaszewski wrote: > On 08/01/2018 11:01 AM, Baolin Wang wrote: [..] > > diff --git a/drivers/leds/trigger/ledtrig-pattern.c b/drivers/leds/trigger/ledtrig-pattern.c [..] > > +static ssize_t pattern_trig_store_pattern(struct device *dev, > > + struct device_attribute *attr, > > + const char *buf, size_t count) > > +{ > > + struct led_classdev *led_cdev = dev_get_drvdata(dev); > > + struct pattern_trig_data *data = led_cdev->trigger_data; > > + int cr, ccount, offset = 0, err = 0; > > + > > + if (!data->hardware_pattern) > > + del_timer_sync(&data->timer); > > + > > + mutex_lock(&data->lock); > > + > > + data->npatterns = 0; > > + while (offset < count - 1 && data->npatterns < MAX_PATTERNS) { > > + cr = 0; > > + ccount = sscanf(buf + offset, "%d %d " PATTERN_SEPARATOR "%n", > > + &data->patterns[data->npatterns].brightness, > > + &data->patterns[data->npatterns].delta_t, &cr); > > In case user makes a typo while constructing list of pattern tuples, > e.g. he forgets a comma, the pattern gets silently truncated. > > User is able to detect the truncation by reading pattern file, > but it is not an immediate feedback anyway. > I agree, a failure to parse the entire pattern should result in an error returned, rather than just silently truncating the pattern. > I propose that pattern format should require number of tuples in the > first position which would allow to get rid of this ambiguity, since > we could verify if the number of parsed tuples is as intended. > I would prefer to see that we check that we have consumed the entire input (accepting optional \n end), rather than having to prepend a count to the string... Regards, Bjorn